Configuring and managing networking
Managing network interfaces, firewalls, and advanced networking features
Abstract
- You can configure bonds, VLANs, bridges, tunnels and other network types to connect the host to the network.
- You can build performance-critical firewalls for the local host and the entire network. RHEL contains packet filtering software, such as the
firewalld
service, thenftables
framework, and Express Data Path (XDP). - RHEL also supports advanced networking features, such as policy-based routing and Multipath TCP (MPTCP).
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Chapter 1. Implementing consistent network interface naming
The udev
device manager implements consistent device naming in Red Hat Enterprise Linux. The device manager supports different naming schemes and, by default, assigns fixed names based on firmware, topology, and location information.
Without consistent device naming, the Linux kernel assigns names to network interfaces by combining a fixed prefix and an index. The index increases as the kernel initializes the network devices. For example, eth0
represents the first Ethernet device being probed on start-up. If you add another network interface controller to the system, the assignment of the kernel device names is no longer fixed because, after a reboot, the devices can initialize in a different order. In that case, the kernel can name the devices differently.
To solve this problem, udev
assigns consistent device names. This has the following advantages:
- Device names are stable across reboots.
- Device names stay fixed even if you add or remove hardware.
- Defective hardware can be seamlessly replaced.
- The network naming is stateless and does not require explicit configuration files.
Generally, Red Hat does not support systems where consistent device naming is disabled. For exceptions, see the Is it safe to set net.ifnames=0 solution.
1.1. How the udev device manager renames network interfaces
To implement a consistent naming scheme for network interfaces, the udev
device manager processes the following rule files in the listed order:
Optional:
/usr/lib/udev/rules.d/60-net.rules
The
/usr/lib/udev/rules.d/60-net.rules
file defines that the deprecated/usr/lib/udev/rename_device
helper utility searches for theHWADDR
parameter in/etc/sysconfig/network-scripts/ifcfg-*
files. If the value set in the variable matches the MAC address of an interface, the helper utility renames the interface to the name set in theDEVICE
parameter of theifcfg
file.If the system uses only NetworkManager connection profiles in keyfile format,
udev
skips this step.Only on Dell systems:
/usr/lib/udev/rules.d/71-biosdevname.rules
This file exists only if the
biosdevname
package is installed, and the rules file defines that thebiosdevname
utility renames the interface according to its naming policy, if it was not renamed in the previous step.NoteInstall and use
biosdevname
only on Dell systems./usr/lib/udev/rules.d/75-net-description.rules
This file defines how
udev
examines the network interface and sets the properties inudev
-internal variables. These variables are then processed in the next step by the/usr/lib/udev/rules.d/80-net-setup-link.rules
file. Some of the properties can be undefined./usr/lib/udev/rules.d/80-net-setup-link.rules
This file calls the
net_setup_link
builtin of theudev
service, andudev
renames the interface based on the order of the policies in theNamePolicy
parameter in the/usr/lib/systemd/network/99-default.link
file. For further details, see Network interface naming policies.If none of the policies applies,
udev
does not rename the interface.
Additional resources
1.2. Network interface naming policies
By default, the udev
device manager uses the /usr/lib/systemd/network/99-default.link
file to determine which device naming policies to apply when it renames interfaces. The NamePolicy
parameter in this file defines which policies udev
uses and in which order:
NamePolicy=kernel database onboard slot path
The following table describes the different actions of udev
based on which policy matches first as specified by the NamePolicy
parameter:
Policy | Description | Example name |
---|---|---|
kernel |
If the kernel indicates that a device name is predictable, |
|
database |
This policy assigns names based on mappings in the |
|
onboard | Device names incorporate firmware or BIOS-provided index numbers for onboard devices. |
|
slot | Device names incorporate firmware or BIOS-provided PCI Express (PCIe) hot-plug slot-index numbers. |
|
path | Device names incorporate the physical location of the connector of the hardware. |
|
mac | Device names incorporate the MAC address. By default, Red Hat Enterprise Linux does not use this policy, but administrators can enable it. |
|
Additional resources
- How the udev device manager renames network interfaces
-
systemd.link(5)
man page
1.3. Network interface naming schemes
The udev
device manager uses certain stable interface attributes that device drivers provide to generate consistent device names.
If a new udev
version changes how the service creates names for certain interfaces, Red Hat adds a new scheme version and documents the details in the systemd.net-naming-scheme(7)
man page. By default, Red Hat Enterprise Linux (RHEL) 8 uses the rhel-8.0
naming scheme, even if you install or update to a later minor version of RHEL.
If you want to use a scheme other than the default, you can switch the network interface naming scheme.
For further details about the naming schemes for different device types and platforms, see the systemd.net-naming-scheme(7)
man page.
1.4. Switching to a different network interface naming scheme
By default, Red Hat Enterprise Linux (RHEL) 8 uses the rhel-8.0
naming scheme, even if you install or update to a later minor version of RHEL. While the default naming scheme fits in most scenarios, there might be reasons to switch to a different scheme version, for example:
- A new scheme can help to better identify a device if it adds additional attributes, such as a slot number, to an interface name.
-
An new scheme can prevent
udev
from falling back to the kernel-assigned device names (eth*
). This happens if the driver does not provide enough unique attributes for two or more interfaces to generate unique names for them.
Prerequisites
- You have access to the console of the server.
Procedure
List the network interfaces:
# ip link show 2: eno1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP mode DEFAULT group default qlen 1000 link/ether 00:00:5e:00:53:1a brd ff:ff:ff:ff:ff:ff ...
Record the MAC addresses of the interfaces.
Optional: Display the
ID_NET_NAMING_SCHEME
property of a network interface to identify the naming scheme that RHEL currently uses:# udevadm info --query=property --property=ID_NET_NAMING_SCHEME /sys/class/net/eno1' ID_NET_NAMING_SCHEME=rhel-8.0
Note that the property is not available on the
lo
loopback device.Append the
net.naming-scheme=<scheme>
option to the command line of all installed kernels, for example:# grubby --update-kernel=ALL --args=net.naming-scheme=rhel-8.4
Reboot the system.
# reboot
Based on the MAC addresses you recorded, identify the new names of network interfaces that have changed due to the different naming scheme:
# ip link show 2: eno1np0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP mode DEFAULT group default qlen 1000 link/ether 00:00:5e:00:53:1a brd ff:ff:ff:ff:ff:ff ...
After switching the scheme,
udev
names in this example the device with MAC address00:00:5e:00:53:1a
eno1np0
, whereas it was namedeno1
before.Identify which NetworkManager connection profile uses an interface with the previous name:
# nmcli -f device,name connection show DEVICE NAME eno1 example_profile ...
Set the
connection.interface-name
property in the connection profile to the new interface name:# nmcli connection modify example_profile connection.interface-name "eno1np0"
Reactivate the connection profile:
# nmcli connection up example_profile
Verification
Identify the naming scheme that RHEL now uses by displaying the
ID_NET_NAMING_SCHEME
property of a network interface:# udevadm info --query=property --property=ID_NET_NAMING_SCHEME /sys/class/net/eno1np0' ID_NET_NAMING_SCHEME=_rhel-8.4
Additional resources
1.5. Determining a predictable RoCE device name on the IBM Z platform
On Red Hat Enterprise Linux (RHEL) 8.7 and later, the udev
device manager sets names for RoCE interfaces on IBM Z as follows:
-
If the host enforces a unique identifier (UID) for a device,
udev
assigns a consistent device name that is based on the UID, for exampleeno<UID_in_decimal>
. If the host does not enforce a UID for a device, the behavior depends on your settings:
-
By default,
udev
uses unpredictable names for the device. -
If you set the
net.naming-scheme=rhel-8.7
kernel command line option,udev
assigns a consistent device name that is based on the function identifier (FID) of the device, for exampleens<FID_in_decimal>
.
-
By default,
Manually configure predictable device name for RoCE interfaces on IBM Z in the following cases:
Your host runs RHEL 8.6 or earlier and enforces a UID for a device, and you plan to update to RHEL 8.7 or later.
After an update to RHEL 8.7 or later,
udev
uses consistent interface names. However, if you used unpredictable device names before the update, NetworkManager connection profiles still use these names and fail to activate until you update the affected profiles.- Your host runs RHEL 8.7 or later and does not enforce a UID, and you plan to upgrade to RHEL 9.
Before you can use a udev
rule or a systemd
link file to rename an interface manually, you must determine a predictable device name.
Prerequisites
- An RoCE controller is installed in the system.
-
The
sysfsutils
package is installed.
Procedure
Display the available network devices, and note the names of the RoCE devices:
# ip link show ... 2: enP5165p0s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP mode DEFAULT group default qlen 1000 ...
Display the device path in the
/sys/
file system:# systool -c net -p Class = "net" Class Device = "enP5165p0s0" Class Device path = "/sys/devices/pci142d:00/142d:00:00.0/net/enP5165p0s0" Device = "142d:00:00.0" Device path = "/sys/devices/pci142d:00/142d:00:00.0"
Use the path shown in the
Device path
field in the next steps.Display the value of the
<device_path>/uid_id_unique
file, for example:# cat /sys/devices/pci142d:00/142d:00:00.0/uid_id_unique
The displayed value indicates whether UID uniqueness is enforced or not, and you require this value in later steps.
Determine a unique identifier:
If UID uniqueness is enforced (
1
), display the UID stored in the<device_path>/uid
file, for example:# cat /sys/devices/pci142d:00/142d:00:00.0/uid
If UID uniqueness is not enforced (
0
), display the FID stored in the<device_path>/function_id
file, for example:# cat /sys/devices/pci142d:00/142d:00:00.0/function_id
The outputs of the commands display the UID and FID values in hexadecimal.
Convert the hexadecimal identifier to decimal, for example:
# printf "%d\n" 0x00001402 5122
To determine the predictable device name, append the identifier in decimal format to the corresponding prefix based on whether UID uniqueness is enforced or not:
-
If UID uniqueness is enforced, append the identifier to the
eno
prefix, for exampleeno5122
. -
If UID uniqueness is not enforced, append the identifier to the
ens
prefix, for exampleens5122
.
-
If UID uniqueness is enforced, append the identifier to the
Next steps
Use one of the following methods to rename the interface to the predictable name:
Additional resources
- IBM documentation: Network interface names
-
systemd.net-naming-scheme(7)
man page
1.6. Customizing the prefix for Ethernet interfaces during installation
If you do not want to use the default device-naming policy for Ethernet interfaces, you can set a custom device prefix during the Red Hat Enterprise Linux (RHEL) installation.
Red Hat supports systems with customized Ethernet prefixes only if you set the prefix during the RHEL installation. Using the prefixdevname
utility on already deployed systems is not supported.
If you set a device prefix during the installation, the udev
service uses the <prefix><index>
format for Ethernet interfaces after the installation. For example, if you set the prefix net
, the service assigns the names net0
, net1
, and so on to the Ethernet interfaces.
The udev
service appends the index to the custom prefix, and preserves the index values of known Ethernet interfaces. If you add an interface, udev
assigns an index value that is one greater than the previously-assigned index value to the new interface.
Prerequisites
- The prefix consists of ASCII characters.
- The prefix is an alphanumeric string.
- The prefix is shorter than 16 characters.
-
The prefix does not conflict with any other well-known network interface prefix, such as
eth
,eno
,ens
, andem
.
Procedure
- Boot the Red Hat Enterprise Linux installation media.
In the boot manager, follow these steps:
-
Select the
Install Red Hat Enterprise Linux <version>
entry. - Press Tab to edit the entry.
-
Append
net.ifnames.prefix=<prefix>
to the kernel options. - Press Enter to start the installation program.
-
Select the
- Install Red Hat Enterprise Linux.
Verification
To verify the interface names, display the network interfaces:
# ip link show ... 2: net0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP mode DEFAULT group default qlen 1000 link/ether 00:00:5e:00:53:1a brd ff:ff:ff:ff:ff:ff ...
Additional resources
1.7. Configuring user-defined network interface names by using udev rules
You can use udev
rules to implement custom network interface names that reflect your organization’s requirements.
Procedure
Identify the network interface that you want to rename:
# ip link show ... enp1s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP mode DEFAULT group default qlen 1000 link/ether 00:00:5e:00:53:1a brd ff:ff:ff:ff:ff:ff ...
Record the MAC address of the interface.
Display the device type ID of the interface:
# cat /sys/class/net/enp1s0/type 1
Create the
/etc/udev/rules.d/70-persistent-net.rules
file, and add a rule for each interface that you want to rename:SUBSYSTEM=="net",ACTION=="add",ATTR{address}=="<MAC_address>",ATTR{type}=="<device_type_id>",NAME="<new_interface_name>"
ImportantUse only
70-persistent-net.rules
as a file name if you require consistent device names during the boot process. Thedracut
utility adds a file with this name to theinitrd
image if you regenerate the RAM disk image.For example, use the following rule to rename the interface with MAC address
00:00:5e:00:53:1a
toprovider0
:SUBSYSTEM=="net",ACTION=="add",ATTR{address}=="00:00:5e:00:53:1a",ATTR{type}=="1",NAME="provider0"
Optional: Regenerate the
initrd
RAM disk image:# dracut -f
You require this step only if you need networking capabilities in the RAM disk. For example, this is the case if the root file system is stored on a network device, such as iSCSI.
Identify which NetworkManager connection profile uses the interface that you want to rename:
# nmcli -f device,name connection show DEVICE NAME enp1s0 example_profile ...
Unset the
connection.interface-name
property in the connection profile:# nmcli connection modify example_profile connection.interface-name ""
Temporarily, configure the connection profile to match both the new and the previous interface name:
# nmcli connection modify example_profile match.interface-name "provider0 enp1s0"
Reboot the system:
# reboot
Verify that the device with the MAC address that you specified in the link file has been renamed to
provider0
:# ip link show provider0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP mode DEFAULT group default qlen 1000 link/ether 00:00:5e:00:53:1a brd ff:ff:ff:ff:ff:ff ...
Configure the connection profile to match only the new interface name:
# nmcli connection modify example_profile match.interface-name "provider0"
You have now removed the old interface name from the connection profile.
Reactivate the connection profile:
# nmcli connection up example_profile
Additional resources
-
udev(7)
man page
1.8. Configuring user-defined network interface names by using systemd link files
You can use systemd
link files to implement custom network interface names that reflect your organization’s requirements.
Prerequisites
- You must meet one of these conditions: NetworkManager does not manage this interface, or the corresponding connection profile uses the keyfile format.
Procedure
Identify the network interface that you want to rename:
# ip link show ... enp1s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP mode DEFAULT group default qlen 1000 link/ether 00:00:5e:00:53:1a brd ff:ff:ff:ff:ff:ff ...
Record the MAC address of the interface.
If it does not already exist, create the
/etc/systemd/network/
directory:# mkdir -p /etc/systemd/network/
For each interface that you want to rename, create a
70-*.link
file in the/etc/systemd/network/
directory with the following content:[Match] MACAddress=<MAC_address> [Link] Name=<new_interface_name>
ImportantUse a file name with a
70-
prefix to keep the file names consistent with theudev
rules-based solution.For example, create the
/etc/systemd/network/70-provider0.link
file with the following content to rename the interface with MAC address00:00:5e:00:53:1a
toprovider0
:[Match] MACAddress=00:00:5e:00:53:1a [Link] Name=provider0
Optional: Regenerate the
initrd
RAM disk image:# dracut -f
You require this step only if you need networking capabilities in the RAM disk. For example, this is the case if the root file system is stored on a network device, such as iSCSI.
Identify which NetworkManager connection profile uses the interface that you want to rename:
# nmcli -f device,name connection show DEVICE NAME enp1s0 example_profile ...
Unset the
connection.interface-name
property in the connection profile:# nmcli connection modify example_profile connection.interface-name ""
Temporarily, configure the connection profile to match both the new and the previous interface name:
# nmcli connection modify example_profile match.interface-name "provider0 enp1s0"
Reboot the system:
# reboot
Verify that the device with the MAC address that you specified in the link file has been renamed to
provider0
:# ip link show provider0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP mode DEFAULT group default qlen 1000 link/ether 00:00:5e:00:53:1a brd ff:ff:ff:ff:ff:ff ...
Configure the connection profile to match only the new interface name:
# nmcli connection modify example_profile match.interface-name "provider0"
You have now removed the old interface name from the connection profile.
Reactivate the connection profile.
# nmcli connection up example_profile
Additional resources
-
systemd.link(5)
man page
1.9. Assigning alternative names to a network interface by using systemd link files
With alternative interface naming, the kernel can assign additional names to network interfaces. You can use these alternative names in the same way as the normal interface names in commands that require a network interface name.
Prerequisites
- You must use ASCII characters for the alternative name.
- The alternative name must be shorter than 128 characters.
Procedure
Display the network interface names and their MAC addresses:
# ip link show ... enp1s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP mode DEFAULT group default qlen 1000 link/ether 00:00:5e:00:53:1a brd ff:ff:ff:ff:ff:ff ...
Record the MAC address of the interface to which you want to assign an alternative name.
If it does not already exist, create the
/etc/systemd/network/
directory:# mkdir -p /etc/systemd/network/
For each interface that must have an alternative name, create a
*.link
file in the/etc/systemd/network/
directory with the following content:[Match] MACAddress=<MAC_address> [Link] AlternativeName=<alternative_interface_name_1> AlternativeName=<alternative_interface_name_2> AlternativeName=<alternative_interface_name_n>
For example, create the
/etc/systemd/network/70-altname.link
file with the following content to assignprovider
as an alternative name to the interface with MAC address00:00:5e:00:53:1a
:[Match] MACAddress=00:00:5e:00:53:1a [Link] AlternativeName=provider
Regenerate the
initrd
RAM disk image:# dracut -f
Reboot the system:
# reboot
Verification
Use the alternative interface name. For example, display the IP address settings of the device with the alternative name
provider
:# ip address show provider 2: enp1s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000 link/ether 00:00:5e:00:53:1a brd ff:ff:ff:ff:ff:ff altname provider ...
Additional resources
Chapter 2. Configuring an Ethernet connection
NetworkManager creates a connection profile for each Ethernet adapter that is installed in a host. By default, this profile uses DHCP for both IPv4 and IPv6 connections. Modify this automatically-created profile or add a new one in the following cases:
- The network requires custom settings, such as a static IP address configuration.
- You require multiple profiles because the host roams among different networks.
Red Hat Enterprise Linux provides administrators different options to configure Ethernet connections. For example:
-
Use
nmcli
to configure connections on the command line. -
Use
nmtui
to configure connections in a text-based user interface. -
Use the GNOME Settings menu or
nm-connection-editor
application to configure connections in a graphical interface. -
Use
nmstatectl
to configure connections through the Nmstate API. - Use RHEL system roles to automate the configuration of connections on one or multiple hosts.
If you want to manually configure Ethernet connections on hosts running in the Microsoft Azure cloud, disable the cloud-init
service or configure it to ignore the network settings retrieved from the cloud environment. Otherwise, cloud-init
will override on the next reboot the network settings that you have manually configured.
2.1. Configuring an Ethernet connection by using nmcli
If you connect a host to the network over Ethernet, you can manage the connection’s settings on the command line by using the nmcli
utility.
Prerequisites
- A physical or virtual Ethernet Network Interface Controller (NIC) exists in the server’s configuration.
Procedure
List the NetworkManager connection profiles:
# nmcli connection show NAME UUID TYPE DEVICE Wired connection 1 a5eb6490-cc20-3668-81f8-0314a27f3f75 ethernet enp1s0
By default, NetworkManager creates a profile for each NIC in the host. If you plan to connect this NIC only to a specific network, adapt the automatically-created profile. If you plan to connect this NIC to networks with different settings, create individual profiles for each network.
If you want to create an additional connection profile, enter:
# nmcli connection add con-name <connection-name> ifname <device-name> type ethernet
Skip this step to modify an existing profile.
Optional: Rename the connection profile:
# nmcli connection modify "Wired connection 1" connection.id "Internal-LAN"
On hosts with multiple profiles, a meaningful name makes it easier to identify the purpose of a profile.
Display the current settings of the connection profile:
# nmcli connection show Internal-LAN ... connection.interface-name: enp1s0 connection.autoconnect: yes ipv4.method: auto ipv6.method: auto ...
Configure the IPv4 settings:
To use DHCP, enter:
# nmcli connection modify Internal-LAN ipv4.method auto
Skip this step if
ipv4.method
is already set toauto
(default).To set a static IPv4 address, network mask, default gateway, DNS servers, and search domain, enter:
# nmcli connection modify Internal-LAN ipv4.method manual ipv4.addresses 192.0.2.1/24 ipv4.gateway 192.0.2.254 ipv4.dns 192.0.2.200 ipv4.dns-search example.com
Configure the IPv6 settings:
To use stateless address autoconfiguration (SLAAC), enter:
# nmcli connection modify Internal-LAN ipv6.method auto
Skip this step if
ipv6.method
is already set toauto
(default).To set a static IPv6 address, network mask, default gateway, DNS servers, and search domain, enter:
# nmcli connection modify Internal-LAN ipv6.method manual ipv6.addresses 2001:db8:1::fffe/64 ipv6.gateway 2001:db8:1::fffe ipv6.dns 2001:db8:1::ffbb ipv6.dns-search example.com
To customize other settings in the profile, use the following command:
# nmcli connection modify <connection-name> <setting> <value>
Enclose values with spaces or semicolons in quotes.
Activate the profile:
# nmcli connection up Internal-LAN
Verification
Display the IP settings of the NIC:
# ip address show enp1s0 2: enp1s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000 link/ether 52:54:00:17:b8:b6 brd ff:ff:ff:ff:ff:ff inet 192.0.2.1/24 brd 192.0.2.255 scope global noprefixroute enp1s0 valid_lft forever preferred_lft forever inet6 2001:db8:1::fffe/64 scope global noprefixroute valid_lft forever preferred_lft forever
Display the IPv4 default gateway:
# ip route show default default via 192.0.2.254 dev enp1s0 proto static metric 102
Display the IPv6 default gateway:
# ip -6 route show default default via 2001:db8:1::ffee dev enp1s0 proto static metric 102 pref medium
Display the DNS settings:
# cat /etc/resolv.conf search example.com nameserver 192.0.2.200 nameserver 2001:db8:1::ffbb
If multiple connection profiles are active at the same time, the order of
nameserver
entries depend on the DNS priority values in these profile and the connection types.Use the
ping
utility to verify that this host can send packets to other hosts:# ping <host-name-or-IP-address>
Troubleshooting
- Verify that the network cable is plugged-in to the host and a switch.
- Check whether the link failure exists only on this host or also on other hosts connected to the same switch.
- Verify that the network cable and the network interface are working as expected. Perform hardware diagnosis steps and replace defect cables and network interface cards.
- If the configuration on the disk does not match the configuration on the device, starting or restarting NetworkManager creates an in-memory connection that reflects the configuration of the device. For further details and how to avoid this problem, see the NetworkManager duplicates a connection after restart of NetworkManager service solution.
Additional resources
-
nm-settings(5)
man page
2.2. Configuring an Ethernet connection by using the nmcli
interactive editor
If you connect a host to the network over Ethernet, you can manage the connection’s settings on the command line by using the nmcli
utility.
Prerequisites
- A physical or virtual Ethernet Network Interface Controller (NIC) exists in the server’s configuration.
Procedure
List the NetworkManager connection profiles:
# nmcli connection show NAME UUID TYPE DEVICE Wired connection 1 a5eb6490-cc20-3668-81f8-0314a27f3f75 ethernet enp1s0
By default, NetworkManager creates a profile for each NIC in the host. If you plan to connect this NIC only to a specific network, adapt the automatically-created profile. If you plan to connect this NIC to networks with different settings, create individual profiles for each network.
Start
nmcli
in interactive mode:To create an additional connection profile, enter:
# nmcli connection edit type ethernet con-name "<connection-name>"
To modify an existing connection profile, enter:
# nmcli connection edit con-name "<connection-name>"
Optional: Rename the connection profile:
nmcli> set connection.id Internal-LAN
On hosts with multiple profiles, a meaningful name makes it easier to identify the purpose of a profile.
Do not use quotes to set an ID that contains spaces to avoid that
nmcli
makes the quotes part of the name. For example, to setExample Connection
as ID, enterset connection.id Example Connection
.Display the current settings of the connection profile:
nmcli> print ... connection.interface-name: enp1s0 connection.autoconnect: yes ipv4.method: auto ipv6.method: auto ...
If you create a new connection profile, set the network interface:
nmcli> set connection.interface-name enp1s0
Configure the IPv4 settings:
To use DHCP, enter:
nmcli> set ipv4.method auto
Skip this step if
ipv4.method
is already set toauto
(default).To set a static IPv4 address, network mask, default gateway, DNS servers, and search domain, enter:
nmcli> ipv4.addresses 192.0.2.1/24 Do you also want to set 'ipv4.method' to 'manual'? [yes]: yes nmcli> ipv4.gateway 192.0.2.254 nmcli> ipv4.dns 192.0.2.200 nmcli> ipv4.dns-search example.com
Configure the IPv6 settings:
To use stateless address autoconfiguration (SLAAC), enter:
nmcli> set ipv6.method auto
Skip this step if
ipv6.method
is already set toauto
(default).To set a static IPv6 address, network mask, default gateway, DNS servers, and search domain, enter:
nmcli> ipv6.addresses 2001:db8:1::fffe/64 Do you also want to set 'ipv6.method' to 'manual'? [yes]: yes nmcli> ipv6.gateway 2001:db8:1::fffe nmcli> ipv6.dns 2001:db8:1::ffbb nmcli> ipv6.dns-search example.com
Save and activate the connection:
nmcli> save persistent
Leave the interactive mode:
nmcli> quit
Verification
Display the IP settings of the NIC:
# ip address show enp1s0 2: enp1s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000 link/ether 52:54:00:17:b8:b6 brd ff:ff:ff:ff:ff:ff inet 192.0.2.1/24 brd 192.0.2.255 scope global noprefixroute enp1s0 valid_lft forever preferred_lft forever inet6 2001:db8:1::fffe/64 scope global noprefixroute valid_lft forever preferred_lft forever
Display the IPv4 default gateway:
# ip route show default default via 192.0.2.254 dev enp1s0 proto static metric 102
Display the IPv6 default gateway:
# ip -6 route show default default via 2001:db8:1::ffee dev enp1s0 proto static metric 102 pref medium
Display the DNS settings:
# cat /etc/resolv.conf search example.com nameserver 192.0.2.200 nameserver 2001:db8:1::ffbb
If multiple connection profiles are active at the same time, the order of
nameserver
entries depend on the DNS priority values in these profile and the connection types.Use the
ping
utility to verify that this host can send packets to other hosts:# ping <host-name-or-IP-address>
Troubleshooting
- Verify that the network cable is plugged-in to the host and a switch.
- Check whether the link failure exists only on this host or also on other hosts connected to the same switch.
- Verify that the network cable and the network interface are working as expected. Perform hardware diagnosis steps and replace defect cables and network interface cards.
- If the configuration on the disk does not match the configuration on the device, starting or restarting NetworkManager creates an in-memory connection that reflects the configuration of the device. For further details and how to avoid this problem, see the NetworkManager duplicates a connection after restart of NetworkManager service solution
Additional resources
-
nm-settings(5)
man page -
nmcli(1)
man page
2.3. Configuring an Ethernet connection by using nmtui
If you connect a host to the network over Ethernet, you can manage the connection’s settings in a text-based user interface by using the nmtui
application. Use nmtui
to create new profiles and to update existing ones on a host without a graphical interface.
In nmtui
:
- Navigate by using the cursor keys.
- Press a button by selecting it and hitting Enter.
- Select and clear checkboxes by using Space.
Prerequisites
- A physical or virtual Ethernet Network Interface Controller (NIC) exists in the server’s configuration.
Procedure
If you do not know the network device name you want to use in the connection, display the available devices:
# nmcli device status DEVICE TYPE STATE CONNECTION enp1s0 ethernet unavailable -- ...
Start
nmtui
:# nmtui
- Select Edit a connection, and press Enter.
Choose whether to add a new connection profile or to modify an existing one:
To create a new profile:
- Press Add.
- Select Ethernet from the list of network types, and press Enter.
- To modify an existing profile, select the profile from the list, and press Enter.
Optional: Update the name of the connection profile.
On hosts with multiple profiles, a meaningful name makes it easier to identify the purpose of a profile.
- If you create a new connection profile, enter the network device name into the Device field.
Depending on your environment, configure the IP address settings in the
IPv4 configuration
andIPv6 configuration
areas accordingly. For this, press the button next to these areas, and select:- Disabled, if this connection does not require an IP address.
- Automatic, if a DHCP server dynamically assigns an IP address to this NIC.
Manual, if the network requires static IP address settings. In this case, you must fill further fields:
- Press Show next to the protocol you want to configure to display additional fields.
Press Add next to Addresses, and enter the IP address and the subnet mask in Classless Inter-Domain Routing (CIDR) format.
If you do not specify a subnet mask, NetworkManager sets a
/32
subnet mask for IPv4 addresses and/64
for IPv6 addresses.- Enter the address of the default gateway.
- Press Add next to DNS servers, and enter the DNS server address.
- Press Add next to Search domains, and enter the DNS search domain.
Figure 2.1. Example of an Ethernet connection with static IP address settings
- Press OK to create and automatically activate the new connection.
- Press Back to return to the main menu.
-
Select Quit, and press Enter to close the
nmtui
application.
Verification
Display the IP settings of the NIC:
# ip address show enp1s0 2: enp1s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000 link/ether 52:54:00:17:b8:b6 brd ff:ff:ff:ff:ff:ff inet 192.0.2.1/24 brd 192.0.2.255 scope global noprefixroute enp1s0 valid_lft forever preferred_lft forever inet6 2001:db8:1::fffe/64 scope global noprefixroute valid_lft forever preferred_lft forever
Display the IPv4 default gateway:
# ip route show default default via 192.0.2.254 dev enp1s0 proto static metric 102
Display the IPv6 default gateway:
# ip -6 route show default default via 2001:db8:1::ffee dev enp1s0 proto static metric 102 pref medium
Display the DNS settings:
# cat /etc/resolv.conf search example.com nameserver 192.0.2.200 nameserver 2001:db8:1::ffbb
If multiple connection profiles are active at the same time, the order of
nameserver
entries depend on the DNS priority values in these profile and the connection types.Use the
ping
utility to verify that this host can send packets to other hosts:# ping <host-name-or-IP-address>
Troubleshooting
- Verify that the network cable is plugged-in to the host and a switch.
- Check whether the link failure exists only on this host or also on other hosts connected to the same switch.
- Verify that the network cable and the network interface are working as expected. Perform hardware diagnosis steps and replace defect cables and network interface cards.
- If the configuration on the disk does not match the configuration on the device, starting or restarting NetworkManager creates an in-memory connection that reflects the configuration of the device. For further details and how to avoid this problem, see the NetworkManager duplicates a connection after restart of NetworkManager service solution.
2.4. Configuring an Ethernet connection by using control-center
If you connect a host to the network over Ethernet, you can manage the connection’s settings with a graphical interface by using the GNOME Settings menu.
Note that control-center
does not support as many configuration options as the nm-connection-editor
application or the nmcli
utility.
Prerequisites
- A physical or virtual Ethernet Network Interface Controller (NIC) exists in the server’s configuration.
- GNOME is installed.
Procedure
-
Press the Super key, enter
Settings
, and press Enter. - Select Network in the navigation on the left.
Choose whether to add a new connection profile or to modify an existing one:
- To create a new profile, click the Ethernet entry. button next to the
- To modify an existing profile, click the gear icon next to the profile entry.
Optional: On the Identity tab, update the name of the connection profile.
On hosts with multiple profiles, a meaningful name makes it easier to identify the purpose of a profile.
Depending on your environment, configure the IP address settings on the IPv4 and IPv6 tabs accordingly:
-
To use DHCP or IPv6 stateless address autoconfiguration (SLAAC), select
Automatic (DHCP)
as method (default). To set a static IP address, network mask, default gateway, DNS servers, and search domain, select
Manual
as method, and fill the fields on the tabs:
-
To use DHCP or IPv6 stateless address autoconfiguration (SLAAC), select
Depending on whether you add or modify a connection profile, click the
or button to save the connection.The GNOME
control-center
automatically activates the connection.
Verification
Display the IP settings of the NIC:
# ip address show enp1s0 2: enp1s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000 link/ether 52:54:00:17:b8:b6 brd ff:ff:ff:ff:ff:ff inet 192.0.2.1/24 brd 192.0.2.255 scope global noprefixroute enp1s0 valid_lft forever preferred_lft forever inet6 2001:db8:1::fffe/64 scope global noprefixroute valid_lft forever preferred_lft forever
Display the IPv4 default gateway:
# ip route show default default via 192.0.2.254 dev enp1s0 proto static metric 102
Display the IPv6 default gateway:
# ip -6 route show default default via 2001:db8:1::ffee dev enp1s0 proto static metric 102 pref medium
Display the DNS settings:
# cat /etc/resolv.conf search example.com nameserver 192.0.2.200 nameserver 2001:db8:1::ffbb
If multiple connection profiles are active at the same time, the order of
nameserver
entries depend on the DNS priority values in these profile and the connection types.Use the
ping
utility to verify that this host can send packets to other hosts:# ping <host-name-or-IP-address>
Troubleshooting steps
- Verify that the network cable is plugged-in to the host and a switch.
- Check whether the link failure exists only on this host or also on other hosts connected to the same switch.
- Verify that the network cable and the network interface are working as expected. Perform hardware diagnosis steps and replace defect cables and network interface cards.
- If the configuration on the disk does not match the configuration on the device, starting or restarting NetworkManager creates an in-memory connection that reflects the configuration of the device. For further details and how to avoid this problem, see the NetworkManager duplicates a connection after restart of NetworkManager service solution.
2.5. Configuring an Ethernet connection by using nm-connection-editor
If you connect a host to the network over Ethernet, you can manage the connection’s settings with a graphical interface by using the nm-connection-editor application.
Prerequisites
- A physical or virtual Ethernet Network Interface Controller (NIC) exists in the server’s configuration.
- GNOME is installed.
Procedure
Open a terminal, and enter:
$ nm-connection-editor
Choose whether to add a new connection profile or to modify an existing one:
To create a new profile:
- Click the button
- Select Ethernet as connection type, and click .
- To modify an existing profile, double-click the profile entry.
Optional: Update the name of the profile in the Connection Name field.
On hosts with multiple profiles, a meaningful name makes it easier to identify the purpose of a profile.
If you create a new profile, select the device on the
Ethernet
tab:Depending on your environment, configure the IP address settings on the IPv4 Settings and IPv6 Settings tabs accordingly:
-
To use DHCP or IPv6 stateless address autoconfiguration (SLAAC), select
Automatic (DHCP)
as method (default). To set a static IP address, network mask, default gateway, DNS servers, and search domain, select
Manual
as method, and fill the fields on the tabs:
-
To use DHCP or IPv6 stateless address autoconfiguration (SLAAC), select
- Click .
- Close nm-connection-editor.
Verification
Display the IP settings of the NIC:
# ip address show enp1s0 2: enp1s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000 link/ether 52:54:00:17:b8:b6 brd ff:ff:ff:ff:ff:ff inet 192.0.2.1/24 brd 192.0.2.255 scope global noprefixroute enp1s0 valid_lft forever preferred_lft forever inet6 2001:db8:1::fffe/64 scope global noprefixroute valid_lft forever preferred_lft forever
Display the IPv4 default gateway:
# ip route show default default via 192.0.2.254 dev enp1s0 proto static metric 102
Display the IPv6 default gateway:
# ip -6 route show default default via 2001:db8:1::ffee dev enp1s0 proto static metric 102 pref medium
Display the DNS settings:
# cat /etc/resolv.conf search example.com nameserver 192.0.2.200 nameserver 2001:db8:1::ffbb
If multiple connection profiles are active at the same time, the order of
nameserver
entries depend on the DNS priority values in these profile and the connection types.Use the
ping
utility to verify that this host can send packets to other hosts:# ping <host-name-or-IP-address>
Troubleshooting steps
- Verify that the network cable is plugged-in to the host and a switch.
- Check whether the link failure exists only on this host or also on other hosts connected to the same switch.
- Verify that the network cable and the network interface are working as expected. Perform hardware diagnosis steps and replace defect cables and network interface cards.
- If the configuration on the disk does not match the configuration on the device, starting or restarting NetworkManager creates an in-memory connection that reflects the configuration of the device. For further details and how to avoid this problem, see the NetworkManager duplicates a connection after restart of NetworkManager service solution.
2.6. Configuring an Ethernet connection with a static IP address by using nmstatectl
Use the nmstatectl
utility to configure an Ethernet connection through the Nmstate API. The Nmstate API ensures that, after setting the configuration, the result matches the configuration file. If anything fails, nmstatectl
automatically rolls back the changes to avoid leaving the system in an incorrect state.
Prerequisites
- A physical or virtual Ethernet Network Interface Controller (NIC) exists in the server’s configuration.
-
The
nmstate
package is installed.
Procedure
Create a YAML file, for example
~/create-ethernet-profile.yml
, with the following content:--- interfaces: - name: enp1s0 type: ethernet state: up ipv4: enabled: true address: - ip: 192.0.2.1 prefix-length: 24 dhcp: false ipv6: enabled: true address: - ip: 2001:db8:1::1 prefix-length: 64 autoconf: false dhcp: false routes: config: - destination: 0.0.0.0/0 next-hop-address: 192.0.2.254 next-hop-interface: enp1s0 - destination: ::/0 next-hop-address: 2001:db8:1::fffe next-hop-interface: enp1s0 dns-resolver: config: search: - example.com server: - 192.0.2.200 - 2001:db8:1::ffbb
These settings define an Ethernet connection profile for the
enp1s0
device with the following settings:-
A static IPv4 address -
192.0.2.1
with the/24
subnet mask -
A static IPv6 address -
2001:db8:1::1
with the/64
subnet mask -
An IPv4 default gateway -
192.0.2.254
-
An IPv6 default gateway -
2001:db8:1::fffe
-
An IPv4 DNS server -
192.0.2.200
-
An IPv6 DNS server -
2001:db8:1::ffbb
-
A DNS search domain -
example.com
-
A static IPv4 address -
Apply the settings to the system:
# nmstatectl apply ~/create-ethernet-profile.yml
Verification
Display the current state in YAML format:
# nmstatectl show enp1s0
Display the IP settings of the NIC:
# ip address show enp1s0 2: enp1s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000 link/ether 52:54:00:17:b8:b6 brd ff:ff:ff:ff:ff:ff inet 192.0.2.1/24 brd 192.0.2.255 scope global noprefixroute enp1s0 valid_lft forever preferred_lft forever inet6 2001:db8:1::fffe/64 scope global noprefixroute valid_lft forever preferred_lft forever
Display the IPv4 default gateway:
# ip route show default default via 192.0.2.254 dev enp1s0 proto static metric 102
Display the IPv6 default gateway:
# ip -6 route show default default via 2001:db8:1::ffee dev enp1s0 proto static metric 102 pref medium
Display the DNS settings:
# cat /etc/resolv.conf search example.com nameserver 192.0.2.200 nameserver 2001:db8:1::ffbb
If multiple connection profiles are active at the same time, the order of
nameserver
entries depend on the DNS priority values in these profile and the connection types.Use the
ping
utility to verify that this host can send packets to other hosts:# ping <host-name-or-IP-address>
Additional resources
-
nmstatectl(8)
man page -
/usr/share/doc/nmstate/examples/
directory
2.7. Configuring an Ethernet connection with a static IP address by using the network
RHEL system role with an interface name
To connect a Red Hat Enterprise Linux host to an Ethernet network, create a NetworkManager connection profile for the network device. By using Ansible and the network
RHEL system role, you can automate this process and remotely configure connection profiles on the hosts defined in a playbook.
You can use the network
RHEL system role to configure an Ethernet connection with static IP addresses, gateways, and DNS settings, and assign them to a specified interface name.
Prerequisites
- You have prepared the control node and the managed nodes
- You are logged in to the control node as a user who can run playbooks on the managed nodes.
-
The account you use to connect to the managed nodes has
sudo
permissions on them. - A physical or virtual Ethernet device exists in the server’s configuration.
- The managed nodes use NetworkManager to configure the network.
Procedure
Create a playbook file, for example
~/playbook.yml
, with the following content:--- - name: Configure the network hosts: managed-node-01.example.com tasks: - name: Ethernet connection profile with static IP address settings ansible.builtin.include_role: name: rhel-system-roles.network vars: network_connections: - name: enp1s0 interface_name: enp1s0 type: ethernet autoconnect: yes ip: address: - 192.0.2.1/24 - 2001:db8:1::1/64 gateway4: 192.0.2.254 gateway6: 2001:db8:1::fffe dns: - 192.0.2.200 - 2001:db8:1::ffbb dns_search: - example.com state: up
For details about all variables used in the playbook, see the
/usr/share/ansible/roles/rhel-system-roles.network/README.md
file on the control node.Validate the playbook syntax:
$ ansible-playbook --syntax-check ~/playbook.yml
Note that this command only validates the syntax and does not protect against a wrong but valid configuration.
Run the playbook:
$ ansible-playbook ~/playbook.yml
Verification
Query the Ansible facts of the managed node and verify the active network settings:
# ansible managed-node-01.example.com -m ansible.builtin.setup ... "ansible_default_ipv4": { "address": "192.0.2.1", "alias": "enp1s0", "broadcast": "192.0.2.255", "gateway": "192.0.2.254", "interface": "enp1s0", "macaddress": "52:54:00:17:b8:b6", "mtu": 1500, "netmask": "255.255.255.0", "network": "192.0.2.0", "prefix": "24", "type": "ether" }, "ansible_default_ipv6": { "address": "2001:db8:1::1", "gateway": "2001:db8:1::fffe", "interface": "enp1s0", "macaddress": "52:54:00:17:b8:b6", "mtu": 1500, "prefix": "64", "scope": "global", "type": "ether" }, ... "ansible_dns": { "nameservers": [ "192.0.2.1", "2001:db8:1::ffbb" ], "search": [ "example.com" ] }, ...
Additional resources
-
/usr/share/ansible/roles/rhel-system-roles.network/README.md
file -
/usr/share/doc/rhel-system-roles/network/
directory
2.8. Configuring an Ethernet connection with a static IP address by using the network
RHEL system role with a device path
To connect a Red Hat Enterprise Linux host to an Ethernet network, create a NetworkManager connection profile for the network device. By using Ansible and the network
RHEL system role, you can automate this process and remotely configure connection profiles on the hosts defined in a playbook.
You can use the network
RHEL system role to configure an Ethernet connection with static IP addresses, gateways, and DNS settings, and assign them to a device based on its path instead of its name.
Prerequisites
- You have prepared the control node and the managed nodes
- You are logged in to the control node as a user who can run playbooks on the managed nodes.
-
The account you use to connect to the managed nodes has
sudo
permissions on them. - A physical or virtual Ethernet device exists in the server’s configuration.
- The managed nodes use NetworkManager to configure the network.
-
You know the path of the device. You can display the device path by using the
udevadm info /sys/class/net/<device_name> | grep ID_PATH=
command.
Procedure
Create a playbook file, for example
~/playbook.yml
, with the following content:--- - name: Configure the network hosts: managed-node-01.example.com tasks: - name: Ethernet connection profile with static IP address settings ansible.builtin.include_role: name: rhel-system-roles.network vars: network_connections: - name: example match: path: - pci-0000:00:0[1-3].0 - &!pci-0000:00:02.0 type: ethernet autoconnect: yes ip: address: - 192.0.2.1/24 - 2001:db8:1::1/64 gateway4: 192.0.2.254 gateway6: 2001:db8:1::fffe dns: - 192.0.2.200 - 2001:db8:1::ffbb dns_search: - example.com state: up
The settings specified in the example playbook include the following:
match
-
Defines that a condition must be met in order to apply the settings. You can only use this variable with the
path
option. path
-
Defines the persistent path of a device. You can set it as a fixed path or an expression. Its value can contain modifiers and wildcards. The example applies the settings to devices that match PCI ID
0000:00:0[1-3].0
, but not0000:00:02.0
.
For details about all variables used in the playbook, see the
/usr/share/ansible/roles/rhel-system-roles.network/README.md
file on the control node.Validate the playbook syntax:
$ ansible-playbook --syntax-check ~/playbook.yml
Note that this command only validates the syntax and does not protect against a wrong but valid configuration.
Run the playbook:
$ ansible-playbook ~/playbook.yml
Verification
Query the Ansible facts of the managed node and verify the active network settings:
# ansible managed-node-01.example.com -m ansible.builtin.setup ... "ansible_default_ipv4": { "address": "192.0.2.1", "alias": "enp1s0", "broadcast": "192.0.2.255", "gateway": "192.0.2.254", "interface": "enp1s0", "macaddress": "52:54:00:17:b8:b6", "mtu": 1500, "netmask": "255.255.255.0", "network": "192.0.2.0", "prefix": "24", "type": "ether" }, "ansible_default_ipv6": { "address": "2001:db8:1::1", "gateway": "2001:db8:1::fffe", "interface": "enp1s0", "macaddress": "52:54:00:17:b8:b6", "mtu": 1500, "prefix": "64", "scope": "global", "type": "ether" }, ... "ansible_dns": { "nameservers": [ "192.0.2.1", "2001:db8:1::ffbb" ], "search": [ "example.com" ] }, ...
Additional resources
-
/usr/share/ansible/roles/rhel-system-roles.network/README.md
file -
/usr/share/doc/rhel-system-roles/network/
directory
2.9. Configuring an Ethernet connection with a dynamic IP address by using nmstatectl
Use the nmstatectl
utility to configure an Ethernet connection through the Nmstate API. The Nmstate API ensures that, after setting the configuration, the result matches the configuration file. If anything fails, nmstatectl
automatically rolls back the changes to avoid leaving the system in an incorrect state.
Prerequisites
- A physical or virtual Ethernet Network Interface Controller (NIC) exists in the server’s configuration.
- A DHCP server is available in the network.
-
The
nmstate
package is installed.
Procedure
Create a YAML file, for example
~/create-ethernet-profile.yml
, with the following content:--- interfaces: - name: enp1s0 type: ethernet state: up ipv4: enabled: true auto-dns: true auto-gateway: true auto-routes: true dhcp: true ipv6: enabled: true auto-dns: true auto-gateway: true auto-routes: true autoconf: true dhcp: true
These settings define an Ethernet connection profile for the
enp1s0
device. The connection retrieves IPv4 addresses, IPv6 addresses, default gateway, routes, DNS servers, and search domains from a DHCP server and IPv6 stateless address autoconfiguration (SLAAC).Apply the settings to the system:
# nmstatectl apply ~/create-ethernet-profile.yml
Verification
Display the current state in YAML format:
# nmstatectl show enp1s0
Display the IP settings of the NIC:
# ip address show enp1s0 2: enp1s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000 link/ether 52:54:00:17:b8:b6 brd ff:ff:ff:ff:ff:ff inet 192.0.2.1/24 brd 192.0.2.255 scope global noprefixroute enp1s0 valid_lft forever preferred_lft forever inet6 2001:db8:1::fffe/64 scope global noprefixroute valid_lft forever preferred_lft forever
Display the IPv4 default gateway:
# ip route show default default via 192.0.2.254 dev enp1s0 proto static metric 102
Display the IPv6 default gateway:
# ip -6 route show default default via 2001:db8:1::ffee dev enp1s0 proto static metric 102 pref medium
Display the DNS settings:
# cat /etc/resolv.conf search example.com nameserver 192.0.2.200 nameserver 2001:db8:1::ffbb
If multiple connection profiles are active at the same time, the order of
nameserver
entries depend on the DNS priority values in these profile and the connection types.Use the
ping
utility to verify that this host can send packets to other hosts:# ping <host-name-or-IP-address>
Additional resources
-
nmstatectl(8)
man page -
/usr/share/doc/nmstate/examples/
directory
2.10. Configuring an Ethernet connection with a dynamic IP address by using the network
RHEL system role with an interface name
To connect a Red Hat Enterprise Linux host to an Ethernet network, create a NetworkManager connection profile for the network device. By using Ansible and the network
RHEL system role, you can automate this process and remotely configure connection profiles on the hosts defined in a playbook.
You can use the network
RHEL system role to configure an Ethernet connection that retrieves its IP addresses, gateways, and DNS settings from a DHCP server and IPv6 stateless address autoconfiguration (SLAAC). With this role you can assign the connection profile to the specified interface name.
Prerequisites
- You have prepared the control node and the managed nodes
- You are logged in to the control node as a user who can run playbooks on the managed nodes.
-
The account you use to connect to the managed nodes has
sudo
permissions on them. - A physical or virtual Ethernet device exists in the server’s configuration.
- A DHCP server and SLAAC are available in the network.
- The managed nodes use the NetworkManager service to configure the network.
Procedure
Create a playbook file, for example
~/playbook.yml
, with the following content:--- - name: Configure the network hosts: managed-node-01.example.com tasks: - name: Ethernet connection profile with dynamic IP address settings ansible.builtin.include_role: name: rhel-system-roles.network vars: network_connections: - name: enp1s0 interface_name: enp1s0 type: ethernet autoconnect: yes ip: dhcp4: yes auto6: yes state: up
The settings specified in the example playbook include the following:
dhcp4: yes
- Enables automatic IPv4 address assignment from DHCP, PPP, or similar services.
auto6: yes
-
Enables IPv6 auto-configuration. By default, NetworkManager uses Router Advertisements. If the router announces the
managed
flag, NetworkManager requests an IPv6 address and prefix from a DHCPv6 server.
For details about all variables used in the playbook, see the
/usr/share/ansible/roles/rhel-system-roles.network/README.md
file on the control node.Validate the playbook syntax:
$ ansible-playbook --syntax-check ~/playbook.yml
Note that this command only validates the syntax and does not protect against a wrong but valid configuration.
Run the playbook:
$ ansible-playbook ~/playbook.yml
Verification
Query the Ansible facts of the managed node and verify that the interface received IP addresses and DNS settings:
# ansible managed-node-01.example.com -m ansible.builtin.setup ... "ansible_default_ipv4": { "address": "192.0.2.1", "alias": "enp1s0", "broadcast": "192.0.2.255", "gateway": "192.0.2.254", "interface": "enp1s0", "macaddress": "52:54:00:17:b8:b6", "mtu": 1500, "netmask": "255.255.255.0", "network": "192.0.2.0", "prefix": "24", "type": "ether" }, "ansible_default_ipv6": { "address": "2001:db8:1::1", "gateway": "2001:db8:1::fffe", "interface": "enp1s0", "macaddress": "52:54:00:17:b8:b6", "mtu": 1500, "prefix": "64", "scope": "global", "type": "ether" }, ... "ansible_dns": { "nameservers": [ "192.0.2.1", "2001:db8:1::ffbb" ], "search": [ "example.com" ] }, ...
Additional resources
-
/usr/share/ansible/roles/rhel-system-roles.network/README.md
file -
/usr/share/doc/rhel-system-roles/network/
directory
2.11. Configuring an Ethernet connection with a dynamic IP address by using the network
RHEL system role with a device path
To connect a Red Hat Enterprise Linux host to an Ethernet network, create a NetworkManager connection profile for the network device. By using Ansible and the network
RHEL system role, you can automate this process and remotely configure connection profiles on the hosts defined in a playbook.
You can use the network
RHEL system role to configure an Ethernet connection that retrieves its IP addresses, gateways, and DNS settings from a DHCP server and IPv6 stateless address autoconfiguration (SLAAC). The role can assign the connection profile to a device based on its path instead of an interface name.
Prerequisites
- You have prepared the control node and the managed nodes
- You are logged in to the control node as a user who can run playbooks on the managed nodes.
-
The account you use to connect to the managed nodes has
sudo
permissions on them. - A physical or virtual Ethernet device exists in the server’s configuration.
- A DHCP server and SLAAC are available in the network.
- The managed hosts use NetworkManager to configure the network.
-
You know the path of the device. You can display the device path by using the
udevadm info /sys/class/net/<device_name> | grep ID_PATH=
command.
Procedure
Create a playbook file, for example
~/playbook.yml
, with the following content:--- - name: Configure the network hosts: managed-node-01.example.com tasks: - name: Ethernet connection profile with dynamic IP address settings ansible.builtin.include_role: name: rhel-system-roles.network vars: network_connections: - name: example match: path: - pci-0000:00:0[1-3].0 - &!pci-0000:00:02.0 type: ethernet autoconnect: yes ip: dhcp4: yes auto6: yes state: up
The settings specified in the example playbook include the following:
match: path
-
Defines that a condition must be met in order to apply the settings. You can only use this variable with the
path
option. path: <path_and_expressions>
-
Defines the persistent path of a device. You can set it as a fixed path or an expression. Its value can contain modifiers and wildcards. The example applies the settings to devices that match PCI ID
0000:00:0[1-3].0
, but not0000:00:02.0
. dhcp4: yes
- Enables automatic IPv4 address assignment from DHCP, PPP, or similar services.
auto6: yes
-
Enables IPv6 auto-configuration. By default, NetworkManager uses Router Advertisements. If the router announces the
managed
flag, NetworkManager requests an IPv6 address and prefix from a DHCPv6 server.
For details about all variables used in the playbook, see the
/usr/share/ansible/roles/rhel-system-roles.network/README.md
file on the control node.Validate the playbook syntax:
$ ansible-playbook --syntax-check ~/playbook.yml
Note that this command only validates the syntax and does not protect against a wrong but valid configuration.
Run the playbook:
$ ansible-playbook ~/playbook.yml
Verification
Query the Ansible facts of the managed node and verify that the interface received IP addresses and DNS settings:
# ansible managed-node-01.example.com -m ansible.builtin.setup ... "ansible_default_ipv4": { "address": "192.0.2.1", "alias": "enp1s0", "broadcast": "192.0.2.255", "gateway": "192.0.2.254", "interface": "enp1s0", "macaddress": "52:54:00:17:b8:b6", "mtu": 1500, "netmask": "255.255.255.0", "network": "192.0.2.0", "prefix": "24", "type": "ether" }, "ansible_default_ipv6": { "address": "2001:db8:1::1", "gateway": "2001:db8:1::fffe", "interface": "enp1s0", "macaddress": "52:54:00:17:b8:b6", "mtu": 1500, "prefix": "64", "scope": "global", "type": "ether" }, ... "ansible_dns": { "nameservers": [ "192.0.2.1", "2001:db8:1::ffbb" ], "search": [ "example.com" ] }, ...
Additional resources
-
/usr/share/ansible/roles/rhel-system-roles.network/README.md
file -
/usr/share/doc/rhel-system-roles/network/
directory
2.12. Configuring multiple Ethernet interfaces by using a single connection profile by interface name
In most cases, one connection profile contains the settings of one network device. However, NetworkManager also supports wildcards when you set the interface name in connection profiles. If a host roams between Ethernet networks with dynamic IP address assignment, you can use this feature to create a single connection profile that you can use for multiple Ethernet interfaces.
Prerequisites
- Multiple physical or virtual Ethernet devices exist in the server’s configuration.
- A DHCP server is available in the network.
- No connection profile exists on the host.
Procedure
Add a connection profile that applies to all interface names starting with
enp
:# nmcli connection add con-name "Wired connection 1" connection.multi-connect multiple match.interface-name enp* type ethernet
Verification
Display all settings of the single connection profile:
# nmcli connection show "Wired connection 1" connection.id: Wired connection 1 ... connection.multi-connect: 3 (multiple) match.interface-name:
enp*
...3
indicates the number of interfaces active on the connection profile at the same time, and not the number of network interfaces in the connection profile. The connection profile uses all devices that match the pattern in thematch.interface-name
parameter and, therefore, the connection profiles have the same Universally Unique Identifier (UUID).Display the status of the connections:
# nmcli connection show NAME UUID TYPE DEVICE ... Wired connection 1 6f22402e-c0cc-49cf-b702-eaf0cd5ea7d1 ethernet enp7s0 Wired connection 1 6f22402e-c0cc-49cf-b702-eaf0cd5ea7d1 ethernet enp8s0 Wired connection 1 6f22402e-c0cc-49cf-b702-eaf0cd5ea7d1 ethernet enp9s0
Additional resources
-
nmcli(1)
man page -
nm-settings(5)
man page
2.13. Configuring a single connection profile for multiple Ethernet interfaces using PCI IDs
The PCI ID is a unique identifier of the devices connected to the system. The connection profile adds multiple devices by matching interfaces based on a list of PCI IDs. You can use this procedure to connect multiple device PCI IDs to the single connection profile.
Prerequisites
- Multiple physical or virtual Ethernet devices exist in the server’s configuration.
- A DHCP server is available in the network.
- No connection profile exists on the host.
Procedure
Identify the device path. For example, to display the device paths of all interfaces starting with
enp
, enter :# udevadm info /sys/class/net/enp | grep ID_PATH=* ... E: ID_PATH=pci-0000:07:00.0 E: ID_PATH=pci-0000:08:00.0
Add a connection profile that applies to all PCI IDs matching the
0000:00:0[7-8].0
expression:# nmcli connection add type ethernet connection.multi-connect multiple match.path "pci-0000:07:00.0 pci-0000:08:00.0" con-name "Wired connection 1"
Verification
Display the status of the connection:
# nmcli connection show NAME UUID TYPE DEVICE Wired connection 1 9cee0958-512f-4203-9d3d-b57af1d88466 ethernet enp7s0 Wired connection 1 9cee0958-512f-4203-9d3d-b57af1d88466 ethernet enp8s0 ...
To display all settings of the connection profile:
# nmcli connection show "Wired connection 1" connection.id: Wired connection 1 ... connection.multi-connect: 3 (multiple) match.path: pci-0000:07:00.0,pci-0000:08:00.0 ...
This connection profile uses all devices with a PCI ID which match the pattern in the
match.path
parameter and, therefore, the connection profiles have the same Universally Unique Identifier (UUID).
Additional resources
-
nmcli(1)
man page -
nm-settings(5)
man page
Chapter 3. Configuring a network bond
A network bond is a method to combine or aggregate physical and virtual network interfaces to provide a logical interface with higher throughput or redundancy. In a bond, the kernel handles all operations exclusively. You can create bonds on different types of devices, such as Ethernet devices or VLANs.
Red Hat Enterprise Linux provides administrators different options to configure team devices. For example:
-
Use
nmcli
to configure bond connections using the command line. - Use the RHEL web console to configure bond connections using a web browser.
-
Use
nmtui
to configure bond connections in a text-based user interface. -
Use the
nm-connection-editor
application to configure bond connections in a graphical interface. -
Use
nmstatectl
to configure bond connections through the Nmstate API. - Use RHEL system roles to automate the bond configuration on one or multiple hosts.
3.1. Understanding the default behavior of controller and port interfaces
Consider the following default behavior when managing or troubleshooting team or bond port interfaces using the NetworkManager
service:
- Starting the controller interface does not automatically start the port interfaces.
- Starting a port interface always starts the controller interface.
- Stopping the controller interface also stops the port interface.
- A controller without ports can start static IP connections.
- A controller without ports waits for ports when starting DHCP connections.
- A controller with a DHCP connection waiting for ports completes when you add a port with a carrier.
- A controller with a DHCP connection waiting for ports continues waiting when you add a port without carrier.
3.2. Upstream switch configuration depending on the bonding modes
Depending on the bonding mode you want to use, you must configure the ports on the switch:
Bonding mode | Configuration on the switch |
---|---|
| Requires static EtherChannel enabled, not Link Aggregation Control Protocol (LACP)-negotiated. |
| No configuration required on the switch. |
| Requires static EtherChannel enabled, not LACP-negotiated. |
| Requires static EtherChannel enabled, not LACP-negotiated. |
| Requires LACP-negotiated EtherChannel enabled. |
| No configuration required on the switch. |
| No configuration required on the switch. |
For details how to configure your switch, see the documentation of the switch.
Certain network bonding features, such as the fail-over mechanism, do not support direct cable connections without a network switch. For further details, see the Is bonding supported with direct connection using crossover cables? KCS solution.
3.3. Configuring a network bond by using nmcli
To configure a network bond on the command line, use the nmcli
utility.
Prerequisites
- Two or more physical or virtual network devices are installed on the server.
- To use Ethernet devices as ports of the bond, the physical or virtual Ethernet devices must be installed on the server.
To use team, bridge, or VLAN devices as ports of the bond, you can either create these devices while you create the bond or you can create them in advance as described in:
Procedure
Create a bond interface:
# nmcli connection add type bond con-name bond0 ifname bond0 bond.options "mode=active-backup"
This command creates a bond named
bond0
that uses theactive-backup
mode.To additionally set a Media Independent Interface (MII) monitoring interval, add the
miimon=interval
option to thebond.options
property, for example:# nmcli connection add type bond con-name bond0 ifname bond0 bond.options "mode=active-backup,miimon=1000"
Display the network interfaces, and note names of interfaces you plan to add to the bond:
# nmcli device status DEVICE TYPE STATE CONNECTION enp7s0 ethernet disconnected -- enp8s0 ethernet disconnected -- bridge0 bridge connected bridge0 bridge1 bridge connected bridge1 ...
In this example:
-
enp7s0
andenp8s0
are not configured. To use these devices as ports, add connection profiles in the next step. -
bridge0
andbridge1
have existing connection profiles. To use these devices as ports, modify their profiles in the next step.
-
Assign interfaces to the bond:
If the interfaces you want to assign to the bond are not configured, create new connection profiles for them:
# nmcli connection add type ethernet slave-type bond con-name bond0-port1 ifname enp7s0 master bond0 # nmcli connection add type ethernet slave-type bond con-name bond0-port2 ifname enp8s0 master bond0
These commands create profiles for
enp7s0
andenp8s0
, and add them to thebond0
connection.To assign an existing connection profile to the bond:
Set the
master
parameter of these connections tobond0
:# nmcli connection modify bridge0 master bond0 # nmcli connection modify bridge1 master bond0
These commands assign the existing connection profiles named
bridge0
andbridge1
to thebond0
connection.Reactivate the connections:
# nmcli connection up bridge0 # nmcli connection up bridge1
Configure the IPv4 settings:
To use this bond device as a port of other devices, enter:
# nmcli connection modify bond0 ipv4.method disabled
- To use DHCP, no action is required.
To set a static IPv4 address, network mask, default gateway, and DNS server to the
bond0
connection, enter:# nmcli connection modify bond0 ipv4.addresses '192.0.2.1/24' ipv4.gateway '192.0.2.254' ipv4.dns '192.0.2.253' ipv4.dns-search 'example.com' ipv4.method manual
Configure the IPv6 settings:
To use this bond device as a port of other devices, enter:
# nmcli connection modify bond0 ipv6.method disabled
- To use stateless address autoconfiguration (SLAAC), no action is required.
To set a static IPv6 address, network mask, default gateway, and DNS server to the
bond0
connection, enter:# nmcli connection modify bond0 ipv6.addresses '2001:db8:1::1/64' ipv6.gateway '2001:db8:1::fffe' ipv6.dns '2001:db8:1::fffd' ipv6.dns-search 'example.com' ipv6.method manual
Optional: If you want to set any parameters on the bond ports, use the following command:
# nmcli connection modify bond0-port1 bond-port.<parameter> <value>
Activate the connection:
# nmcli connection up bond0
Verify that the ports are connected, and the
CONNECTION
column displays the port’s connection name:# nmcli device DEVICE TYPE STATE CONNECTION ... enp7s0 ethernet connected bond0-port1 enp8s0 ethernet connected bond0-port2
When you activate any port of the connection, NetworkManager also activates the bond, but not the other ports of it. You can configure that Red Hat Enterprise Linux enables all ports automatically when the bond is enabled:
Enable the
connection.autoconnect-slaves
parameter of the bond’s connection:# nmcli connection modify bond0 connection.autoconnect-slaves 1
Reactivate the bridge:
# nmcli connection up bond0
Verification
Temporarily remove the network cable from one of the network devices and check if the other device in the bond handling the traffic.
Note that there is no method to properly test link failure events using software utilities. Tools that deactivate connections, such as
nmcli
, show only the bonding driver’s ability to handle port configuration changes and not actual link failure events.Display the status of the bond:
# cat /proc/net/bonding/bond0
3.4. Configuring a network bond by using the RHEL web console
Use the RHEL web console to configure a network bond if you prefer to manage network settings using a web browser-based interface.
Prerequisites
- Two or more physical or virtual network devices are installed on the server.
- To use Ethernet devices as members of the bond, the physical or virtual Ethernet devices must be installed on the server.
To use team, bridge, or VLAN devices as members of the bond, create them in advance as described in:
You have installed the RHEL 8 web console.
For instructions, see Installing and enabling the web console.
Procedure
Log in to the RHEL 8 web console.
For details, see Logging in to the web console.
- Select the Networking tab in the navigation on the left side of the screen.
- Click Interfaces section. in the
- Enter the name of the bond device you want to create.
- Select the interfaces that should be members of the bond.
Select the mode of the bond.
If you select Active backup, the web console shows the additional field Primary in which you can select the preferred active device.
-
Set the link monitoring mode. For example, when you use the Adaptive load balancing mode, set it to
ARP
. Optional: Adjust the monitoring interval, link up delay, and link down delay settings. Typically, you only change the defaults for troubleshooting purposes.
- Click .
By default, the bond uses a dynamic IP address. If you want to set a static IP address:
- Click the name of the bond in the Interfaces section.
- Click Edit next to the protocol you want to configure.
- Select Manual next to Addresses, and enter the IP address, prefix, and default gateway.
- In the DNS section, click the button, and enter the IP address of the DNS server. Repeat this step to set multiple DNS servers.
- In the DNS search domains section, click the button, and enter the search domain.
If the interface requires static routes, configure them in the Routes section.
- Click
Verification
Select the Networking tab in the navigation on the left side of the screen, and check if there is incoming and outgoing traffic on the interface:
Temporarily remove the network cable from one of the network devices and check if the other device in the bond handling the traffic.
Note that there is no method to properly test link failure events using software utilities. Tools that deactivate connections, such as the web console, show only the bonding driver’s ability to handle member configuration changes and not actual link failure events.
Display the status of the bond:
# cat /proc/net/bonding/bond0
3.5. Configuring a network bond by using nmtui
The nmtui
application provides a text-based user interface for NetworkManager. You can use nmtui
to configure a network bond on a host without a graphical interface.
In nmtui
:
- Navigate by using the cursor keys.
- Press a button by selecting it and hitting Enter.
- Select and clear checkboxes by using Space.
Prerequisites
- Two or more physical or virtual network devices are installed on the server.
- To use Ethernet devices as ports of the bond, the physical or virtual Ethernet devices must be installed on the server.
Procedure
If you do not know the network device names on which you want configure a network bond, display the available devices:
# nmcli device status DEVICE TYPE STATE CONNECTION enp7s0 ethernet unavailable -- enp8s0 ethernet unavailable -- ...
Start
nmtui
:# nmtui
- Select Edit a connection, and press Enter.
- Press Add.
- Select Bond from the list of network types, and press Enter.
Optional: Enter a name for the NetworkManager profile to be created.
On hosts with multiple profiles, a meaningful name makes it easier to identify the purpose of a profile.
- Enter the bond device name to be created into the Device field.
Add ports to the bond to be created:
- Press Add next to the Slaves list.
- Select the type of the interface you want to add as port to the bond, for example, Ethernet.
- Optional: Enter a name for the NetworkManager profile to be created for this bond port.
- Enter the port’s device name into the Device field.
Press OK to return to the window with the bond settings.
Figure 3.1. Adding an Ethernet device as port to a bond
- Repeat these steps to add more ports to the bond.
-
Set the bond mode. Depending on the value you set,
nmtui
displays additional fields for settings that are related to the selected mode. Depending on your environment, configure the IP address settings in the IPv4 configuration and IPv6 configuration areas accordingly. For this, press the button next to these areas, and select:
-
Disabled
, if the bond does not require an IP address. -
Automatic
, if a DHCP server or stateless address autoconfiguration (SLAAC) dynamically assigns an IP address to the bond. Manual
, if the network requires static IP address settings. In this case, you must fill further fields:- Press Show next to the protocol you want to configure to display additional fields.
Press Add next to Addresses, and enter the IP address and the subnet mask in Classless Inter-Domain Routing (CIDR) format.
If you do not specify a subnet mask, NetworkManager sets a
/32
subnet mask for IPv4 addresses and/64
for IPv6 addresses.- Enter the address of the default gateway.
- Press Add next to DNS servers, and enter the DNS server address.
- Press Add next to Search domains, and enter the DNS search domain.
Figure 3.2. Example of a bond connection with static IP address settings
-
- Press OK to create and automatically activate the new connection.
- Press Back to return to the main menu.
-
Select Quit, and press Enter to close the
nmtui
application.
Verification
Temporarily remove the network cable from one of the network devices and check if the other device in the bond handling the traffic.
Note that there is no method to properly test link failure events using software utilities. Tools that deactivate connections, such as
nmcli
, show only the bonding driver’s ability to handle port configuration changes and not actual link failure events.Display the status of the bond:
# cat /proc/net/bonding/bond0
3.6. Configuring a network bond by using nm-connection-editor
If you use Red Hat Enterprise Linux with a graphical interface, you can configure network bonds using the nm-connection-editor
application.
Note that nm-connection-editor
can add only new ports to a bond. To use an existing connection profile as a port, create the bond by using the nmcli
utility as described in Configuring a network bond by using nmcli.
Prerequisites
- Two or more physical or virtual network devices are installed on the server.
- To use Ethernet devices as ports of the bond, the physical or virtual Ethernet devices must be installed on the server.
- To use team, bond, or VLAN devices as ports of the bond, ensure that these devices are not already configured.
Procedure
Open a terminal, and enter
nm-connection-editor
:$ nm-connection-editor
- Click the button to add a new connection.
- Select the Bond connection type, and click .
On the Bond tab:
- Optional: Set the name of the bond interface in the Interface name field.
Click the
button to add a network interface as a port to the bond.- Select the connection type of the interface. For example, select Ethernet for a wired connection.
- Optional: Set a connection name for the port.
- If you create a connection profile for an Ethernet device, open the Ethernet tab, and select in the Device field the network interface you want to add as a port to the bond. If you selected a different device type, configure it accordingly. Note that you can only use Ethernet interfaces in a bond that are not configured.
- Click .
Repeat the previous step for each interface you want to add to the bond:
- Optional: Set other options, such as the Media Independent Interface (MII) monitoring interval.
Configure the IP address settings on both the IPv4 Settings and IPv6 Settings tabs:
- To use this bridge device as a port of other devices, set the Method field to Disabled.
- To use DHCP, leave the Method field at its default, Automatic (DHCP).
To use static IP settings, set the Method field to Manual and fill the fields accordingly:
- Click .
-
Close
nm-connection-editor
.
Verification
Temporarily remove the network cable from one of the network devices and check if the other device in the bond handling the traffic.
Note that there is no method to properly test link failure events using software utilities. Tools that deactivate connections, such as
nmcli
, show only the bonding driver’s ability to handle port configuration changes and not actual link failure events.Display the status of the bond:
# cat /proc/net/bonding/bond0
3.7. Configuring a network bond by using nmstatectl
Use the nmstatectl
utility to configure a network bond through the Nmstate API. The Nmstate API ensures that, after setting the configuration, the result matches the configuration file. If anything fails, nmstatectl
automatically rolls back the changes to avoid leaving the system in an incorrect state.
Depending on your environment, adjust the YAML file accordingly. For example, to use different devices than Ethernet adapters in the bond, adapt the base-iface
attribute and type
attributes of the ports you use in the bond.
Prerequisites
- Two or more physical or virtual network devices are installed on the server.
- To use Ethernet devices as ports in the bond, the physical or virtual Ethernet devices must be installed on the server.
-
To use team, bridge, or VLAN devices as ports in the bond, set the interface name in the
port
list, and define the corresponding interfaces. -
The
nmstate
package is installed.
Procedure
Create a YAML file, for example
~/create-bond.yml
, with the following content:--- interfaces: - name: bond0 type: bond state: up ipv4: enabled: true address: - ip: 192.0.2.1 prefix-length: 24 dhcp: false ipv6: enabled: true address: - ip: 2001:db8:1::1 prefix-length: 64 autoconf: false dhcp: false link-aggregation: mode: active-backup port: - enp1s0 - enp7s0 - name: enp1s0 type: ethernet state: up - name: enp7s0 type: ethernet state: up routes: config: - destination: 0.0.0.0/0 next-hop-address: 192.0.2.254 next-hop-interface: bond0 - destination: ::/0 next-hop-address: 2001:db8:1::fffe next-hop-interface: bond0 dns-resolver: config: search: - example.com server: - 192.0.2.200 - 2001:db8:1::ffbb
These settings define a network bond with the following settings:
-
Network interfaces in the bond:
enp1s0
andenp7s0
-
Mode:
active-backup
-
Static IPv4 address:
192.0.2.1
with a/24
subnet mask -
Static IPv6 address:
2001:db8:1::1
with a/64
subnet mask -
IPv4 default gateway:
192.0.2.254
-
IPv6 default gateway:
2001:db8:1::fffe
-
IPv4 DNS server:
192.0.2.200
-
IPv6 DNS server:
2001:db8:1::ffbb
-
DNS search domain:
example.com
-
Network interfaces in the bond:
Apply the settings to the system:
# nmstatectl apply ~/create-bond.yml
Verification
Display the status of the devices and connections:
# nmcli device status DEVICE TYPE STATE CONNECTION bond0 bond connected bond0
Display all settings of the connection profile:
# nmcli connection show bond0 connection.id: bond0 connection.uuid: 79cbc3bd-302e-4b1f-ad89-f12533b818ee connection.stable-id: -- connection.type: bond connection.interface-name: bond0 ...
Display the connection settings in YAML format:
# nmstatectl show bond0
Additional resources
-
nmstatectl(8)
man page -
/usr/share/doc/nmstate/examples/
directory
3.8. Configuring a network bond by using the network
RHEL system role
You can combine network interfaces in a bond to provide a logical interface with higher throughput or redundancy. To configure a bond, create a NetworkManager connection profile. By using Ansible and the network
RHEL system role, you can automate this process and remotely configure connection profiles on the hosts defined in a playbook.
You can use the network
RHEL system role to configure a network bond and, if a connection profile for the bond’s parent device does not exist, the role can create it as well.
Prerequisites
- You have prepared the control node and the managed nodes
- You are logged in to the control node as a user who can run playbooks on the managed nodes.
-
The account you use to connect to the managed nodes has
sudo
permissions on them. - Two or more physical or virtual network devices are installed on the server.
Procedure
Create a playbook file, for example
~/playbook.yml
, with the following content:--- - name: Configure the network hosts: managed-node-01.example.com tasks: - name: Bond connection profile with two Ethernet ports ansible.builtin.include_role: name: rhel-system-roles.network vars: network_connections: # Bond profile - name: bond0 type: bond interface_name: bond0 ip: dhcp4: yes auto6: yes bond: mode: active-backup state: up # Port profile for the 1st Ethernet device - name: bond0-port1 interface_name: enp7s0 type: ethernet controller: bond0 state: up # Port profile for the 2nd Ethernet device - name: bond0-port2 interface_name: enp8s0 type: ethernet controller: bond0 state: up
The settings specified in the example playbook include the following:
type: <profile_type>
- Sets the type of the profile to create. The example playbook creates three connection profiles: One for the bond and two for the Ethernet devices.
dhcp4: yes
- Enables automatic IPv4 address assignment from DHCP, PPP, or similar services.
auto6: yes
-
Enables IPv6 auto-configuration. By default, NetworkManager uses Router Advertisements. If the router announces the
managed
flag, NetworkManager requests an IPv6 address and prefix from a DHCPv6 server. mode: <bond_mode>
Sets the bonding mode. Possible values are:
-
balance-rr
(default) -
active-backup
-
balance-xor
-
broadcast
-
802.3ad
-
balance-tlb
-
balance-alb
.
Depending on the mode you set, you need to set additional variables in the playbook.
-
For details about all variables used in the playbook, see the
/usr/share/ansible/roles/rhel-system-roles.network/README.md
file on the control node.Validate the playbook syntax:
$ ansible-playbook --syntax-check ~/playbook.yml
Note that this command only validates the syntax and does not protect against a wrong but valid configuration.
Run the playbook:
$ ansible-playbook ~/playbook.yml
Verification
Temporarily remove the network cable from one of the network devices and check if the other device in the bond handling the traffic.
Note that there is no method to properly test link failure events using software utilities. Tools that deactivate connections, such as
nmcli
, show only the bonding driver’s ability to handle port configuration changes and not actual link failure events.
Additional resources
-
/usr/share/ansible/roles/rhel-system-roles.network/README.md
file -
/usr/share/doc/rhel-system-roles/network/
directory
3.9. Creating a network bond to enable switching between an Ethernet and wireless connection without interrupting the VPN
RHEL users who connect their workstation to their company’s network typically use a VPN to access remote resources. However, if the workstation switches between an Ethernet and Wi-Fi connection, for example, if you release a laptop from a docking station with an Ethernet connection, the VPN connection is interrupted. To avoid this problem, you can create a network bond that uses the Ethernet and Wi-Fi connection in active-backup
mode.
Prerequisites
- The host contains an Ethernet and a Wi-Fi device.
An Ethernet and Wi-Fi NetworkManager connection profile has been created and both connections work independently.
This procedure uses the following connection profiles to create a network bond named
bond0
:-
Docking_station
associated with theenp11s0u1
Ethernet device -
Wi-Fi
associated with thewlp1s0
Wi-Fi device
-
Procedure
Create a bond interface in
active-backup
mode:# nmcli connection add type bond con-name bond0 ifname bond0 bond.options "mode=active-backup"
This command names both the interface and connection profile
bond0
.Configure the IPv4 settings of the bond:
- If a DHCP server in your network assigns IPv4 addresses to hosts, no action is required.
If your local network requires static IPv4 addresses, set the address, network mask, default gateway, DNS server, and DNS search domain to the
bond0
connection:# nmcli connection modify bond0 ipv4.addresses '192.0.2.1/24' # nmcli connection modify bond0 ipv4.gateway '192.0.2.254' # nmcli connection modify bond0 ipv4.dns '192.0.2.253' # nmcli connection modify bond0 ipv4.dns-search 'example.com' # nmcli connection modify bond0 ipv4.method manual
Configure the IPv6 settings of the bond:
- If your router or a DHCP server in your network assigns IPv6 addresses to hosts, no action is required.
If your local network requires static IPv6 addresses, set the address, network mask, default gateway, DNS server, and DNS search domain to the
bond0
connection:# nmcli connection modify bond0 ipv6.addresses '2001:db8:1::1/64' # nmcli connection modify bond0 ipv6.gateway '2001:db8:1::fffe' # nmcli connection modify bond0 ipv6.dns '2001:db8:1::fffd' # nmcli connection modify bond0 ipv6.dns-search 'example.com' # nmcli connection modify bond0 ipv6.method manual
Display the connection profiles:
# nmcli connection show NAME UUID TYPE DEVICE Docking_station 256dd073-fecc-339d-91ae-9834a00407f9 ethernet enp11s0u1 Wi-Fi 1f1531c7-8737-4c60-91af-2d21164417e8 wifi wlp1s0 ...
You require the names of the connection profiles and the Ethernet device name in the next steps.
Assign the connection profile of the Ethernet connection to the bond:
# nmcli connection modify Docking_station master bond0
Assign the connection profile of the Wi-Fi connection to the bond:
# nmcli connection modify Wi-Fi master bond0
If your Wi-Fi network uses MAC filtering to allow only MAC addresses on a allow list to access the network, configure that NetworkManager dynamically assigns the MAC address of the active port to the bond:
# nmcli connection modify bond0 +bond.options fail_over_mac=1
With this setting, you must set only the MAC address of the Wi-Fi device to the allow list instead of the MAC address of both the Ethernet and Wi-Fi device.
Set the device associated with the Ethernet connection as primary device of the bond:
# nmcli con modify bond0 +bond.options "primary=enp11s0u1"
With this setting, the bond always uses the Ethernet connection if it is available.
Configure that NetworkManager automatically activates ports when the
bond0
device is activated:# nmcli connection modify bond0 connection.autoconnect-slaves 1
Activate the
bond0
connection:# nmcli connection up bond0
Verification
Display the currently active device, the status of the bond and its ports:
# cat /proc/net/bonding/bond0 Ethernet Channel Bonding Driver: v3.7.1 (April 27, 2011) Bonding Mode: fault-tolerance (active-backup) (fail_over_mac active) Primary Slave: enp11s0u1 (primary_reselect always) Currently Active Slave: enp11s0u1 MII Status: up MII Polling Interval (ms): 1 Up Delay (ms): 0 Down Delay (ms): 0 Peer Notification Delay (ms): 0 Slave Interface: enp11s0u1 MII Status: up Speed: 1000 Mbps Duplex: full Link Failure Count: 0 Permanent HW addr: 00:53:00:59:da:b7 Slave queue ID: 0 Slave Interface: wlp1s0 MII Status: up Speed: Unknown Duplex: Unknown Link Failure Count: 2 Permanent HW addr: 00:53:00:b3:22:ba Slave queue ID: 0
Additional resources
3.10. The different network bonding modes
The Linux bonding driver provides link aggregation. Bonding is the process of aggregating multiple network interfaces in parallel to provide a single logical bonded interface. The actions of a bonded interface depend on the bonding policy that is also known as mode. The different modes provide either load-balancing or hot standby services.
The following modes exist:
- Balance-rr (Mode 0)
Balance-rr
uses the round-robin algorithm that sequentially transmits packets from the first available port to the last one. This mode provides load balancing and fault tolerance.This mode requires switch configuration of a port aggregation group, also called EtherChannel or similar port grouping. An EtherChannel is a port link aggregation technology to group multiple physical Ethernet links to one logical Ethernet link.
The drawback of this mode is that it is not suitable for heavy workloads and if TCP throughput or ordered packet delivery is essential.
- Active-backup (Mode 1)
Active-backup
uses the policy that determines that only one port is active in the bond. This mode provides fault tolerance and does not require any switch configuration.If the active port fails, an alternate port becomes active. The bond sends a gratuitous address resolution protocol (ARP) response to the network. The gratuitous ARP forces the receiver of the ARP frame to update their forwarding table. The
Active-backup
mode transmits a gratuitous ARP to announce the new path to maintain connectivity for the host.The
primary
option defines the preferred port of the bonding interface.- Balance-xor (Mode 2)
Balance-xor
uses the selected transmit hash policy to send the packets. This mode provides load balancing, fault tolerance, and requires switch configuration to set up an Etherchannel or similar port grouping.To alter packet transmission and balance transmit, this mode uses the
xmit_hash_policy
option. Depending on the source or destination of traffic on the interface, the interface requires an additional load-balancing configuration. See description xmit_hash_policy bonding parameter.- Broadcast (Mode 3)
Broadcast
uses a policy that transmits every packet on all interfaces. This mode provides fault tolerance and requires a switch configuration to set up an EtherChannel or similar port grouping.The drawback of this mode is that it is not suitable for heavy workloads and if TCP throughput or ordered packet delivery is essential.
- 802.3ad (Mode 4)
802.3ad
uses the same-named IEEE standard dynamic link aggregation policy. This mode provides fault tolerance. This mode requires switch configuration to set up a Link Aggregation Control Protocol (LACP) port grouping.This mode creates aggregation groups that share the same speed and duplex settings and utilizes all ports in the active aggregator. Depending on the source or destination of traffic on the interface, this mode requires an additional load-balancing configuration.
By default, the port selection for outgoing traffic depends on the transmit hash policy. Use the
xmit_hash_policy
option of the transmit hash policy to change the port selection and balance transmit.The difference between the
802.3ad
and theBalance-xor
is compliance. The802.3ad
policy negotiates LACP between the port aggregation groups. See description xmit_hash_policy bonding parameter- Balance-tlb (Mode 5)
Balance-tlb
uses the transmit load balancing policy. This mode provides fault tolerance, load balancing, and establishes channel bonding that does not require any switch support.The active port receives the incoming traffic. In case of failure of the active port, another one takes over the MAC address of the failed port. To decide which interface processes the outgoing traffic, use one of the following modes:
-
Value
0
: Uses the hash distribution policy to distribute traffic without load balancing Value
1
: Distributes traffic to each port by using load balancingWith the bonding option
tlb_dynamic_lb=0
, this bonding mode uses thexmit_hash_policy
bonding option to balance transmit. Theprimary
option defines the preferred port of the bonding interface.
See description xmit_hash_policy bonding parameter.
-
Value
- Balance-alb (Mode 6)
Balance-alb
uses an adaptive load balancing policy. This mode provides fault tolerance, load balancing, and does not require any special switch support.This mode Includes balance-transmit load balancing (
balance-tlb
) and receive-load balancing for IPv4 and IPv6 traffic. The bonding intercepts ARP replies sent by the local system and overwrites the source hardware address of one of the ports in the bond. ARP negotiation manages the receive-load balancing. Therefore, different ports use different hardware addresses for the server.The
primary
option defines the preferred port of the bonding interface. With the bonding optiontlb_dynamic_lb=0
, this bonding mode uses thexmit_hash_policy
bonding option to balance transmit. See description xmit_hash_policy bonding parameter.
Additional resources
-
/usr/share/doc/kernel-doc-<version>/Documentation/networking/bonding.rst
provided by thekernel-doc
package -
/usr/share/doc/kernel-doc-<version>/Documentation/networking/bonding.txt
provided by thekernel-doc
package - Which bonding modes work when used with a bridge that virtual machine guests or containers connect to?
- How are the values for different policies in "xmit_hash_policy" bonding parameter calculated?
3.11. The xmit_hash_policy bonding parameter
The xmit_hash_policy
load balancing parameter selects the transmit hash policy for a node selection in the balance-xor
, 802.3ad
, balance-alb
, and balance-tlb
modes. It is only applicable to mode 5 and 6 if the tlb_dynamic_lb parameter is 0
. The possible values of this parameter are layer2
, layer2+3
, layer3+4
, encap2+3
, encap3+4
, and vlan+srcmac
.
Refer the table for details:
Policy or Network layers | Layer2 | Layer2+3 | Layer3+4 | encap2+3 | encap3+4 | VLAN+srcmac |
Uses | XOR of source and destination MAC addresses and Ethernet protocol type | XOR of source and destination MAC addresses and IP addresses | XOR of source and destination ports and IP addresses |
XOR of source and destination MAC addresses and IP addresses inside a supported tunnel, for example, Virtual Extensible LAN (VXLAN). This mode relies on |
XOR of source and destination ports and IP addresses inside a supported tunnel, for example, VXLAN. This mode relies on | XOR of VLAN ID and source MAC vendor and source MAC device |
Placement of traffic | All traffic to a particular network peer on the same underlying network interface | All traffic to a particular IP address on the same underlying network interface | All traffic to a particular IP address and port on the same underlying network interface | |||
Primary choice | If network traffic is between this system and multiple other systems in the same broadcast domain | If network traffic between this system and multiple other systems goes through a default gateway | If network traffic between this system and another system uses the same IP addresses but goes through multiple ports | The encapsulated traffic is between the source system and multiple other systems using multiple IP addresses | The encapsulated traffic is between the source system and other systems using multiple port numbers | If the bond carries network traffic, from multiple containers or virtual machines (VM), that expose their MAC address directly to the external network such as the bridge network, and you can not configure a switch for Mode 2 or Mode 4 |
Secondary choice | If network traffic is mostly between this system and multiple other systems behind a default gateway | If network traffic is mostly between this system and another system | ||||
Compliant | 802.3ad | 802.3ad | Not 802.3ad | |||
Default policy | This is the default policy if no configuration is provided |
For non-IP traffic, the formula is the same as for the |
For non-IP traffic, the formula is the same as for the |
Chapter 4. Configuring a NIC team
Network interface controller (NIC) teaming is a method to combine or aggregate physical and virtual network interfaces to provide a logical interface with higher throughput or redundancy. NIC teaming uses a small kernel module to implement fast handling of packet flows and a user-space service for other tasks. This way, NIC teaming is an easily extensible and scalable solution for load-balancing and redundancy requirements.
Red Hat Enterprise Linux provides administrators different options to configure team devices. For example:
-
Use
nmcli
to configure teams connections using the command line. - Use the RHEL web console to configure team connections using a web browser.
-
Use the
nm-connection-editor
application to configure team connections in a graphical interface.
NIC teaming is deprecated in Red Hat Enterprise Linux 9. If you plan to upgrade your server to a future version of RHEL, consider using the kernel bonding driver as an alternative. For details, see Configuring a network bond.
4.1. Understanding the default behavior of controller and port interfaces
Consider the following default behavior when managing or troubleshooting team or bond port interfaces using the NetworkManager
service:
- Starting the controller interface does not automatically start the port interfaces.
- Starting a port interface always starts the controller interface.
- Stopping the controller interface also stops the port interface.
- A controller without ports can start static IP connections.
- A controller without ports waits for ports when starting DHCP connections.
- A controller with a DHCP connection waiting for ports completes when you add a port with a carrier.
- A controller with a DHCP connection waiting for ports continues waiting when you add a port without carrier.
4.2. Understanding the teamd service, runners, and link-watchers
The team service, teamd
, controls one instance of the team driver. This instance of the driver adds instances of a hardware device driver to form a team of network interfaces. The team driver presents a network interface, for example team0
, to the kernel.
The teamd
service implements the common logic to all methods of teaming. Those functions are unique to the different load sharing and backup methods, such as round-robin, and implemented by separate units of code referred to as runners
. Administrators specify runners in JavaScript Object Notation (JSON) format, and the JSON code is compiled into an instance of teamd
when the instance is created. Alternatively, when using NetworkManager
, you can set the runner in the team.runner
parameter, and NetworkManager
auto-creates the corresponding JSON code.
The following runners are available:
-
broadcast
: Transmits data over all ports. -
roundrobin
: Transmits data over all ports in turn. -
activebackup
: Transmits data over one port while the others are kept as a backup. -
loadbalance
: Transmits data over all ports with active Tx load balancing and Berkeley Packet Filter (BPF)-based Tx port selectors. -
random
: Transmits data on a randomly selected port. -
lacp
: Implements the 802.3ad Link Aggregation Control Protocol (LACP).
The teamd
services uses a link watcher to monitor the state of subordinate devices. The following link-watchers are available:
-
ethtool
: Thelibteam
library uses theethtool
utility to watch for link state changes. This is the default link-watcher. -
arp_ping
: Thelibteam
library uses thearp_ping
utility to monitor the presence of a far-end hardware address using Address Resolution Protocol (ARP). -
nsna_ping
: On IPv6 connections, thelibteam
library uses the Neighbor Advertisement and Neighbor Solicitation features from the IPv6 Neighbor Discovery protocol to monitor the presence of a neighbor’s interface.
Each runner can use any link watcher, with the exception of lacp
. This runner can only use the ethtool
link watcher.
4.3. Configuring a NIC team by using nmcli
To configure a network interface controller (NIC) team on the command line, use the nmcli
utility.
NIC teaming is deprecated in Red Hat Enterprise Linux 9. If you plan to upgrade your server to a future version of RHEL, consider using the kernel bonding driver as an alternative. For details, see Configuring a network bond.
Prerequisites
-
The
teamd
andNetworkManager-team
packages are installed. - Two or more physical or virtual network devices are installed on the server.
- To use Ethernet devices as ports of the team, the physical or virtual Ethernet devices must be installed on the server and connected to a switch.
To use bond, bridge, or VLAN devices as ports of the team, you can either create these devices while you create the team or you can create them in advance as described in:
Procedure
Create a team interface:
# nmcli connection add type team con-name team0 ifname team0 team.runner activebackup
This command creates a NIC team named
team0
that uses theactivebackup
runner.Optional: Set a link watcher. For example, to set the
ethtool
link watcher in theteam0
connection profile:# nmcli connection modify team0 team.link-watchers "name=ethtool"
Link watchers support different parameters. To set parameters for a link watcher, specify them space-separated in the
name
property. Note that the name property must be surrounded by quotation marks. For example, to use theethtool
link watcher and set itsdelay-up
parameter to2500
milliseconds (2.5 seconds):# nmcli connection modify team0 team.link-watchers "name=ethtool delay-up=2500"
To set multiple link watchers and each of them with specific parameters, the link watchers must be separated by a comma. The following example sets the
ethtool
link watcher with thedelay-up
parameter and thearp_ping
link watcher with thesource-host
andtarget-host
parameter:# nmcli connection modify team0 team.link-watchers "name=ethtool delay-up=2, name=arp_ping source-host=192.0.2.1 target-host=192.0.2.2"
Display the network interfaces, and note the names of the interfaces you want to add to the team:
# nmcli device status DEVICE TYPE STATE CONNECTION enp7s0 ethernet disconnected -- enp8s0 ethernet disconnected -- bond0 bond connected bond0 bond1 bond connected bond1 ...
In this example:
-
enp7s0
andenp8s0
are not configured. To use these devices as ports, add connection profiles in the next step. Note that you can only use Ethernet interfaces in a team that are not assigned to any connection. -
bond0
andbond1
have existing connection profiles. To use these devices as ports, modify their profiles in the next step.
-
Assign the port interfaces to the team:
If the interfaces you want to assign to the team are not configured, create new connection profiles for them:
# nmcli connection add type ethernet slave-type team con-name team0-port1 ifname enp7s0 master team0 # nmcli connection add type ethernet slave--type team con-name team0-port2 ifname enp8s0 master team0
These commands create profiles for
enp7s0
andenp8s0
, and add them to theteam0
connection.To assign an existing connection profile to the team:
Set the
master
parameter of these connections toteam0
:# nmcli connection modify bond0 master team0 # nmcli connection modify bond1 master team0
These commands assign the existing connection profiles named
bond0
andbond1
to theteam0
connection.Reactivate the connections:
# nmcli connection up bond0 # nmcli connection up bond1
Configure the IPv4 settings:
To use this team device as a port of other devices, enter:
# nmcli connection modify team0 ipv4.method disabled
- To use DHCP, no action is required.
To set a static IPv4 address, network mask, default gateway, and DNS server to the
team0
connection, enter:# nmcli connection modify team0 ipv4.addresses '192.0.2.1/24' ipv4.gateway '192.0.2.254' ipv4.dns '192.0.2.253' ipv4.dns-search 'example.com' ipv4.method manual
Configure the IPv6 settings:
To use this team device as a port of other devices, enter:
# nmcli connection modify team0 ipv6.method disabled
- To use stateless address autoconfiguration (SLAAC), no action is required.
To set a static IPv6 address, network mask, default gateway, and DNS server to the
team0
connection, enter:# nmcli connection modify team0 ipv6.addresses '2001:db8:1::1/64' ipv6.gateway '2001:db8:1::fffe' ipv6.dns '2001:db8:1::fffd' ipv6.dns-search 'example.com' ipv6.method manual
Activate the connection:
# nmcli connection up team0
Verification
Display the status of the team:
# teamdctl team0 state setup: runner: activebackup ports: enp7s0 link watches: link summary: up instance[link_watch_0]: name: ethtool link: up down count: 0 enp8s0 link watches: link summary: up instance[link_watch_0]: name: ethtool link: up down count: 0 runner: active port: enp7s0
In this example, both ports are up.
Additional resources
- Configuring NetworkManager to avoid using a specific profile to provide a default gateway
- Understanding the teamd service, runners, and link-watchers
-
nm-settings(5)
man page -
teamd.conf(5)
man page
4.4. Configuring a NIC team by using the RHEL web console
Use the RHEL web console to configure a network interface controller (NIC) team if you prefer to manage network settings using a web browser-based interface.
NIC teaming is deprecated in Red Hat Enterprise Linux 9. If you plan to upgrade your server to a future version of RHEL, consider using the kernel bonding driver as an alternative. For details, see Configuring a network bond.
Prerequisites
-
The
teamd
andNetworkManager-team
packages are installed. - Two or more physical or virtual network devices are installed on the server.
- To use Ethernet devices as ports of the team, the physical or virtual Ethernet devices must be installed on the server and connected to a switch.
To use bond, bridge, or VLAN devices as ports of the team, create them in advance as described in:
You have installed the RHEL 8 web console.
For instructions, see Installing and enabling the web console.
Procedure
Log in to the RHEL 8 web console.
For details, see Logging in to the web console.
-
Select the
Networking
tab in the navigation on the left side of the screen. -
Click
Interfaces
section. in the - Enter the name of the team device you want to create.
- Select the interfaces that should be ports of the team.
Select the runner of the team.
If you select
Load balancing
or802.3ad LACP
, the web console shows the additional fieldBalancer
.Set the link watcher:
-
If you select
Ethtool
, additionally, set a link up and link down delay. -
If you set
ARP ping
orNSNA ping
, additionally, set a ping interval and ping target.
-
If you select
- Click .
By default, the team uses a dynamic IP address. If you want to set a static IP address:
-
Click the name of the team in the
Interfaces
section. -
Click
Edit
next to the protocol you want to configure. -
Select
Manual
next toAddresses
, and enter the IP address, prefix, and default gateway. -
In the
DNS
section, click the button, and enter the IP address of the DNS server. Repeat this step to set multiple DNS servers. -
In the
DNS search domains
section, click the button, and enter the search domain. If the interface requires static routes, configure them in the
Routes
section.- Click
-
Click the name of the team in the
Verification
Select the
Networking
tab in the navigation on the left side of the screen, and check if there is incoming and outgoing traffic on the interface.Display the status of the team:
# teamdctl team0 state setup: runner: activebackup ports: enp7s0 link watches: link summary: up instance[link_watch_0]: name: ethtool link: up down count: 0 enp8s0 link watches: link summary: up instance[link_watch_0]: name: ethtool link: up down count: 0 runner: active port: enp7s0
In this example, both ports are up.
Additional resources
4.5. Configuring a NIC team by using nm-connection-editor
If you use Red Hat Enterprise Linux with a graphical interface, you can configure network interface controller (NIC) teams using the nm-connection-editor
application.
Note that nm-connection-editor
can add only new ports to a team. To use an existing connection profile as a port, create the team using the nmcli
utility as described in Configuring a NIC team by using nmcli.
NIC teaming is deprecated in Red Hat Enterprise Linux 9. If you plan to upgrade your server to a future version of RHEL, consider using the kernel bonding driver as an alternative. For details, see Configuring a network bond.
Prerequisites
-
The
teamd
andNetworkManager-team
packages are installed. - Two or more physical or virtual network devices are installed on the server.
- To use Ethernet devices as ports of the team, the physical or virtual Ethernet devices must be installed on the server.
- To use team, bond, or VLAN devices as ports of the team, ensure that these devices are not already configured.
Procedure
Open a terminal, and enter
nm-connection-editor
:$ nm-connection-editor
- Click the button to add a new connection.
- Select the Team connection type, and click .
On the Team tab:
- Optional: Set the name of the team interface in the Interface name field.
Click the
button to add a new connection profile for a network interface and adding the profile as a port to the team.- Select the connection type of the interface. For example, select Ethernet for a wired connection.
- Optional: Set a connection name for the port.
- If you create a connection profile for an Ethernet device, open the Ethernet tab, and select in the Device field the network interface you want to add as a port to the team. If you selected a different device type, configure it accordingly. Note that you can only use Ethernet interfaces in a team that are not assigned to any connection.
- Click .
Repeat the previous step for each interface you want to add to the team.
Click the
button to set advanced options to the team connection.- On the Runner tab, select the runner.
- On the Link Watcher tab, set the link watcher and its optional settings.
- Click .
Configure the IP address settings on both the IPv4 Settings and IPv6 Settings tabs:
- To use this bridge device as a port of other devices, set the Method field to Disabled.
- To use DHCP, leave the Method field at its default, Automatic (DHCP).
To use static IP settings, set the Method field to Manual and fill the fields accordingly:
- Click .
-
Close
nm-connection-editor
.
Verification
Display the status of the team:
# teamdctl team0 state setup: runner: activebackup ports: enp7s0 link watches: link summary: up instance[link_watch_0]: name: ethtool link: up down count: 0 enp8s0 link watches: link summary: up instance[link_watch_0]: name: ethtool link: up down count: 0 runner: active port: enp7s0
Additional resources
- Configuring a network bond by using nm-connection-editor
- Configuring a NIC team by using nm-connection-editor
- Configuring VLAN tagging by using nm-connection-editor
- Configuring NetworkManager to avoid using a specific profile to provide a default gateway
- Understanding the teamd service, runners, and link-watchers
- NetworkManager duplicates a connection after restart of NetworkManager service
Chapter 5. Configuring VLAN tagging
A Virtual Local Area Network (VLAN) is a logical network within a physical network. The VLAN interface tags packets with the VLAN ID as they pass through the interface, and removes tags of returning packets. You create VLAN interfaces on top of another interface, such as Ethernet, bond, team, or bridge devices. These interfaces are called the parent interface
.
Red Hat Enterprise Linux provides administrators different options to configure VLAN devices. For example:
-
Use
nmcli
to configure VLAN tagging using the command line. - Use the RHEL web console to configure VLAN tagging using a web browser.
-
Use
nmtui
to configure VLAN tagging in a text-based user interface. -
Use the
nm-connection-editor
application to configure connections in a graphical interface. -
Use
nmstatectl
to configure connections through the Nmstate API. - Use RHEL system roles to automate the VLAN configuration on one or multiple hosts.
5.1. Configuring VLAN tagging by using nmcli
You can configure Virtual Local Area Network (VLAN) tagging on the command line using the nmcli
utility.
Prerequisites
- The interface you plan to use as a parent to the virtual VLAN interface supports VLAN tags.
If you configure the VLAN on top of a bond interface:
- The ports of the bond are up.
-
The bond is not configured with the
fail_over_mac=follow
option. A VLAN virtual device cannot change its MAC address to match the parent’s new MAC address. In such a case, the traffic would still be sent with the incorrect source MAC address. -
The bond is usually not expected to get IP addresses from a DHCP server or IPv6 auto-configuration. Ensure it by setting the
ipv4.method=disable
andipv6.method=ignore
options while creating the bond. Otherwise, if DHCP or IPv6 auto-configuration fails after some time, the interface might be brought down.
- The switch, the host is connected to, is configured to support VLAN tags. For details, see the documentation of your switch.
Procedure
Display the network interfaces:
# nmcli device status DEVICE TYPE STATE CONNECTION enp1s0 ethernet disconnected enp1s0 bridge0 bridge connected bridge0 bond0 bond connected bond0 ...
Create the VLAN interface. For example, to create a VLAN interface named
vlan10
that usesenp1s0
as its parent interface and that tags packets with VLAN ID10
, enter:# nmcli connection add type vlan con-name vlan10 ifname vlan10 vlan.parent enp1s0 vlan.id 10
Note that the VLAN must be within the range from
0
to4094
.By default, the VLAN connection inherits the maximum transmission unit (MTU) from the parent interface. Optionally, set a different MTU value:
# nmcli connection modify vlan10 ethernet.mtu 2000
Configure the IPv4 settings:
To use this VLAN device as a port of other devices, enter:
# nmcli connection modify vlan10 ipv4.method disabled
- To use DHCP, no action is required.
To set a static IPv4 address, network mask, default gateway, and DNS server to the
vlan10
connection, enter:# nmcli connection modify vlan10 ipv4.addresses '192.0.2.1/24' ipv4.gateway '192.0.2.254' ipv4.dns '192.0.2.253' ipv4.method manual
Configure the IPv6 settings:
To use this VLAN device as a port of other devices, enter:
# nmcli connection modify vlan10 ipv6.method disabled
- To use stateless address autoconfiguration (SLAAC), no action is required.
To set a static IPv6 address, network mask, default gateway, and DNS server to the
vlan10
connection, enter:# nmcli connection modify vlan10 ipv6.addresses '2001:db8:1::1/32' ipv6.gateway '2001:db8:1::fffe' ipv6.dns '2001:db8:1::fffd' ipv6.method manual
Activate the connection:
# nmcli connection up vlan10
Verification
Verify the settings:
# ip -d addr show vlan10 4: vlan10@enp1s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000 link/ether 52:54:00:72:2f:6e brd ff:ff:ff:ff:ff:ff promiscuity 0 vlan protocol 802.1Q id 10 <REORDER_HDR> numtxqueues 1 numrxqueues 1 gso_max_size 65536 gso_max_segs 65535 inet 192.0.2.1/24 brd 192.0.2.255 scope global noprefixroute vlan10 valid_lft forever preferred_lft forever inet6 2001:db8:1::1/32 scope global noprefixroute valid_lft forever preferred_lft forever inet6 fe80::8dd7:9030:6f8e:89e6/64 scope link noprefixroute valid_lft forever preferred_lft forever
Additional resources
-
nm-settings(5)
man page
5.2. Configuring VLAN tagging by using the RHEL web console
You can configure VLAN tagging if you prefer to manage network settings using a web browser-based interface in the RHEL web console.
Prerequisites
- The interface you plan to use as a parent to the virtual VLAN interface supports VLAN tags.
If you configure the VLAN on top of a bond interface:
- The ports of the bond are up.
-
The bond is not configured with the
fail_over_mac=follow
option. A VLAN virtual device cannot change its MAC address to match the parent’s new MAC address. In such a case, the traffic would still be sent with the incorrect source MAC address. - The bond is usually not expected to get IP addresses from a DHCP server or IPv6 auto-configuration. Ensure it by disabling the IPv4 and IPv6 protocol creating the bond. Otherwise, if DHCP or IPv6 auto-configuration fails after some time, the interface might be brought down.
- The switch, the host is connected to, is configured to support VLAN tags. For details, see the documentation of your switch.
You have installed the RHEL 8 web console.
For instructions, see Installing and enabling the web console.
Procedure
Log in to the RHEL 8 web console.
For details, see Logging in to the web console.
-
Select the
Networking
tab in the navigation on the left side of the screen. -
Click
Interfaces
section. in the - Select the parent device.
- Enter the VLAN ID.
Enter the name of the VLAN device or keep the automatically-generated name.
- Click .
By default, the VLAN device uses a dynamic IP address. If you want to set a static IP address:
-
Click the name of the VLAN device in the
Interfaces
section. -
Click
Edit
next to the protocol you want to configure. -
Select
Manual
next toAddresses
, and enter the IP address, prefix, and default gateway. -
In the
DNS
section, click the button, and enter the IP address of the DNS server. Repeat this step to set multiple DNS servers. -
In the
DNS search domains
section, click the button, and enter the search domain. If the interface requires static routes, configure them in the
Routes
section.- Click
-
Click the name of the VLAN device in the
Verification
Select the
Networking
tab in the navigation on the left side of the screen, and check if there is incoming and outgoing traffic on the interface:
5.3. Configuring VLAN tagging by using nmtui
The nmtui
application provides a text-based user interface for NetworkManager. You can use nmtui
to configure VLAN tagging on a host without a graphical interface.
In nmtui
:
- Navigate by using the cursor keys.
- Press a button by selecting it and hitting Enter.
- Select and clear checkboxes by using Space.
Prerequisites
- The interface you plan to use as a parent to the virtual VLAN interface supports VLAN tags.
If you configure the VLAN on top of a bond interface:
- The ports of the bond are up.
-
The bond is not configured with the
fail_over_mac=follow
option. A VLAN virtual device cannot change its MAC address to match the parent’s new MAC address. In such a case, the traffic would still be sent with the then incorrect source MAC address. -
The bond is usually not expected to get IP addresses from a DHCP server or IPv6 auto-configuration. Ensure it by setting the
ipv4.method=disable
andipv6.method=ignore
options while creating the bond. Otherwise, if DHCP or IPv6 auto-configuration fails after some time, the interface might be brought down.
- The switch the host is connected to is configured to support VLAN tags. For details, see the documentation of your switch.
Procedure
If you do not know the network device name on which you want configure VLAN tagging, display the available devices:
# nmcli device status DEVICE TYPE STATE CONNECTION enp1s0 ethernet unavailable -- ...
Start
nmtui
:# nmtui
- Select Edit a connection, and press Enter.
- Press Add.
- Select VLAN from the list of network types, and press Enter.
Optional: Enter a name for the NetworkManager profile to be created.
On hosts with multiple profiles, a meaningful name makes it easier to identify the purpose of a profile.
- Enter the VLAN device name to be created into the Device field.
- Enter the name of the device on which you want to configure VLAN tagging into the Parent field.
-
Enter the VLAN ID. The ID must be within the range from
0
to4094
. Depending on your environment, configure the IP address settings in the IPv4 configuration and IPv6 configuration areas accordingly. For this, press the button next to these areas, and select:
-
Disabled
, if this VLAN device does not require an IP address or you want to use it as a port of other devices. -
Automatic
, if a DHCP server or stateless address autoconfiguration (SLAAC) dynamically assigns an IP address to the VLAN device. Manual
, if the network requires static IP address settings. In this case, you must fill further fields:- Press Show next to the protocol you want to configure to display additional fields.
Press Add next to Addresses, and enter the IP address and the subnet mask in Classless Inter-Domain Routing (CIDR) format.
If you do not specify a subnet mask, NetworkManager sets a
/32
subnet mask for IPv4 addresses and/64
for IPv6 addresses.- Enter the address of the default gateway.
- Press Add next to DNS servers, and enter the DNS server address.
- Press Add next to Search domains, and enter the DNS search domain.
Figure 5.1. Example of a VLAN connection with static IP address settings
-
- Press OK to create and automatically activate the new connection.
- Press Back to return to the main menu.
-
Select Quit, and press Enter to close the
nmtui
application.
Verification
Verify the settings:
# ip -d addr show vlan10 4: vlan10@enp1s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000 link/ether 52:54:00:72:2f:6e brd ff:ff:ff:ff:ff:ff promiscuity 0 vlan protocol 802.1Q id 10 <REORDER_HDR> numtxqueues 1 numrxqueues 1 gso_max_size 65536 gso_max_segs 65535 inet 192.0.2.1/24 brd 192.0.2.255 scope global noprefixroute vlan10 valid_lft forever preferred_lft forever inet6 2001:db8:1::1/32 scope global noprefixroute valid_lft forever preferred_lft forever inet6 fe80::8dd7:9030:6f8e:89e6/64 scope link noprefixroute valid_lft forever preferred_lft forever
5.4. Configuring VLAN tagging by using nm-connection-editor
You can configure Virtual Local Area Network (VLAN) tagging in a graphical interface using the nm-connection-editor
application.
Prerequisites
- The interface you plan to use as a parent to the virtual VLAN interface supports VLAN tags.
If you configure the VLAN on top of a bond interface:
- The ports of the bond are up.
-
The bond is not configured with the
fail_over_mac=follow
option. A VLAN virtual device cannot change its MAC address to match the parent’s new MAC address. In such a case, the traffic would still be sent with the incorrect source MAC address.
- The switch, the host is connected, to is configured to support VLAN tags. For details, see the documentation of your switch.
Procedure
Open a terminal, and enter
nm-connection-editor
:$ nm-connection-editor
- Click the button to add a new connection.
- Select the VLAN connection type, and click .
On the VLAN tab:
- Select the parent interface.
- Select the VLAN id. Note that the VLAN must be within the range from 0 to 4094.
- By default, the VLAN connection inherits the maximum transmission unit (MTU) from the parent interface. Optionally, set a different MTU value.
Optional: Set the name of the VLAN interface and further VLAN-specific options.
Configure the IP address settings on both the IPv4 Settings and IPv6 Settings tabs:
- To use this bridge device as a port of other devices, set the Method field to Disabled.
- To use DHCP, leave the Method field at its default, Automatic (DHCP).
To use static IP settings, set the Method field to Manual and fill the fields accordingly:
- Click .
-
Close
nm-connection-editor
.
Verification
Verify the settings:
# ip -d addr show vlan10 4: vlan10@enp1s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000 link/ether 52:54:00:d5:e0:fb brd ff:ff:ff:ff:ff:ff promiscuity 0 vlan protocol 802.1Q id 10 <REORDER_HDR> numtxqueues 1 numrxqueues 1 gso_max_size 65536 gso_max_segs 65535 inet 192.0.2.1/24 brd 192.0.2.255 scope global noprefixroute vlan10 valid_lft forever preferred_lft forever inet6 2001:db8:1::1/32 scope global noprefixroute valid_lft forever preferred_lft forever inet6 fe80::8dd7:9030:6f8e:89e6/64 scope link noprefixroute valid_lft forever preferred_lft forever
5.5. Configuring VLAN tagging by using nmstatectl
Use the nmstatectl
utility to configure Virtual Local Area Network VLAN through the Nmstate API. The Nmstate API ensures that, after setting the configuration, the result matches the configuration file. If anything fails, nmstatectl
automatically rolls back the changes to avoid leaving the system in an incorrect state.
Depending on your environment, adjust the YAML file accordingly. For example, to use different devices than Ethernet adapters in the VLAN, adapt the base-iface
attribute and type
attributes of the ports you use in the VLAN.
Prerequisites
- To use Ethernet devices as ports in the VLAN, the physical or virtual Ethernet devices must be installed on the server.
-
The
nmstate
package is installed.
Procedure
Create a YAML file, for example
~/create-vlan.yml
, with the following content:--- interfaces: - name: vlan10 type: vlan state: up ipv4: enabled: true address: - ip: 192.0.2.1 prefix-length: 24 dhcp: false ipv6: enabled: true address: - ip: 2001:db8:1::1 prefix-length: 64 autoconf: false dhcp: false vlan: base-iface: enp1s0 id: 10 - name: enp1s0 type: ethernet state: up routes: config: - destination: 0.0.0.0/0 next-hop-address: 192.0.2.254 next-hop-interface: vlan10 - destination: ::/0 next-hop-address: 2001:db8:1::fffe next-hop-interface: vlan10 dns-resolver: config: search: - example.com server: - 192.0.2.200 - 2001:db8:1::ffbb
These settings define a VLAN with ID 10 that uses the
enp1s0
device. As the child device, the VLAN connection has the following settings:-
A static IPv4 address -
192.0.2.1
with the/24
subnet mask -
A static IPv6 address -
2001:db8:1::1
with the/64
subnet mask -
An IPv4 default gateway -
192.0.2.254
-
An IPv6 default gateway -
2001:db8:1::fffe
-
An IPv4 DNS server -
192.0.2.200
-
An IPv6 DNS server -
2001:db8:1::ffbb
-
A DNS search domain -
example.com
-
A static IPv4 address -
Apply the settings to the system:
# nmstatectl apply ~/create-vlan.yml
Verification
Display the status of the devices and connections:
# nmcli device status DEVICE TYPE STATE CONNECTION vlan10 vlan connected vlan10
Display all settings of the connection profile:
# nmcli connection show vlan10 connection.id: vlan10 connection.uuid: 1722970f-788e-4f81-bd7d-a86bf21c9df5 connection.stable-id: -- connection.type: vlan connection.interface-name: vlan10 ...
Display the connection settings in YAML format:
# nmstatectl show vlan0
Additional resources
-
nmstatectl(8)
man page -
/usr/share/doc/nmstate/examples/
directory
5.6. Configuring VLAN tagging by using the network
RHEL system role
If your network uses Virtual Local Area Networks (VLANs) to separate network traffic into logical networks, create a NetworkManager connection profile to configure VLAN tagging. By using Ansible and the network
RHEL system role, you can automate this process and remotely configure connection profiles on the hosts defined in a playbook.
You can use the network
RHEL system role to configure VLAN tagging and, if a connection profile for the VLAN’s parent device does not exists, the role can create it as well.
If the VLAN device requires an IP address, default gateway, and DNS settings, configure them on the VLAN device and not on the parent device.
Prerequisites
- You have prepared the control node and the managed nodes
- You are logged in to the control node as a user who can run playbooks on the managed nodes.
-
The account you use to connect to the managed nodes has
sudo
permissions on them.
Procedure
Create a playbook file, for example
~/playbook.yml
, with the following content:--- - name: Configure the network hosts: managed-node-01.example.com tasks: - name: VLAN connection profile with Ethernet port ansible.builtin.include_role: name: rhel-system-roles.network vars: network_connections: # Ethernet profile - name: enp1s0 type: ethernet interface_name: enp1s0 autoconnect: yes state: up ip: dhcp4: no auto6: no # VLAN profile - name: enp1s0.10 type: vlan vlan: id: 10 ip: dhcp4: yes auto6: yes parent: enp1s0 state: up
e settings specified in the example playbook include the following:
type: <profile_type>
- Sets the type of the profile to create. The example playbook creates two connection profiles: One for the parent Ethernet device and one for the VLAN device.
dhcp4: <value>
-
If set to
yes
, automatic IPv4 address assignment from DHCP, PPP, or similar services is enabled. Disable the IP address configuration on the parent device. auto6: <value>
-
If set to
yes
, IPv6 auto-configuration is enabled. In this case, by default, NetworkManager uses Router Advertisements and, if the router announces themanaged
flag, NetworkManager requests an IPv6 address and prefix from a DHCPv6 server. Disable the IP address configuration on the parent device. parent: <parent_device>
- Sets the parent device of the VLAN connection profile. In the example, the parent is the Ethernet interface.
For details about all variables used in the playbook, see the
/usr/share/ansible/roles/rhel-system-roles.network/README.md
file on the control node.Validate the playbook syntax:
$ ansible-playbook --syntax-check ~/playbook.yml
Note that this command only validates the syntax and does not protect against a wrong but valid configuration.
Run the playbook:
$ ansible-playbook ~/playbook.yml
Verification
Verify the VLAN settings:
# ansible managed-node-01.example.com -m command -a 'ip -d addr show enp1s0.10' managed-node-01.example.com | CHANGED | rc=0 >> 4: vlan10@enp1s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000 link/ether 52:54:00:72:2f:6e brd ff:ff:ff:ff:ff:ff promiscuity 0 vlan protocol 802.1Q id 10 <REORDER_HDR> numtxqueues 1 numrxqueues 1 gso_max_size 65536 gso_max_segs 65535 ...
Additional resources
-
/usr/share/ansible/roles/rhel-system-roles.network/README.md
file -
/usr/share/doc/rhel-system-roles/network/
directory
Chapter 6. Configuring a network bridge
A network bridge is a link-layer device which forwards traffic between networks based on a table of MAC addresses. The bridge builds the MAC addresses table by listening to network traffic and thereby learning what hosts are connected to each network. For example, you can use a software bridge on a Red Hat Enterprise Linux host to emulate a hardware bridge or in virtualization environments, to integrate virtual machines (VM) to the same network as the host.
A bridge requires a network device in each network the bridge should connect. When you configure a bridge, the bridge is called controller
and the devices it uses ports
.
You can create bridges on different types of devices, such as:
- Physical and virtual Ethernet devices
- Network bonds
- Network teams
- VLAN devices
Due to the IEEE 802.11 standard which specifies the use of 3-address frames in Wi-Fi for the efficient use of airtime, you cannot configure a bridge over Wi-Fi networks operating in Ad-Hoc or Infrastructure modes.
6.1. Configuring a network bridge by using nmcli
To configure a network bridge on the command line, use the nmcli
utility.
Prerequisites
- Two or more physical or virtual network devices are installed on the server.
- To use Ethernet devices as ports of the bridge, the physical or virtual Ethernet devices must be installed on the server.
To use team, bond, or VLAN devices as ports of the bridge, you can either create these devices while you create the bridge or you can create them in advance as described in:
Procedure
Create a bridge interface:
# nmcli connection add type bridge con-name bridge0 ifname bridge0
This command creates a bridge named
bridge0
, enter:Display the network interfaces, and note the names of the interfaces you want to add to the bridge:
# nmcli device status DEVICE TYPE STATE CONNECTION enp7s0 ethernet disconnected -- enp8s0 ethernet disconnected -- bond0 bond connected bond0 bond1 bond connected bond1 ...
In this example:
-
enp7s0
andenp8s0
are not configured. To use these devices as ports, add connection profiles in the next step. -
bond0
andbond1
have existing connection profiles. To use these devices as ports, modify their profiles in the next step.
-
Assign the interfaces to the bridge.
If the interfaces you want to assign to the bridge are not configured, create new connection profiles for them:
# nmcli connection add type ethernet slave-type bridge con-name bridge0-port1 ifname enp7s0 master bridge0 # nmcli connection add type ethernet slave-type bridge con-name bridge0-port2 ifname enp8s0 master bridge0
These commands create profiles for
enp7s0
andenp8s0
, and add them to thebridge0
connection.If you want to assign an existing connection profile to the bridge:
Set the
master
parameter of these connections tobridge0
:# nmcli connection modify bond0 master bridge0 # nmcli connection modify bond1 master bridge0
These commands assign the existing connection profiles named
bond0
andbond1
to thebridge0
connection.Reactivate the connections:
# nmcli connection up bond0 # nmcli connection up bond1
Configure the IPv4 settings:
To use this bridge device as a port of other devices, enter:
# nmcli connection modify bridge0 ipv4.method disabled
- To use DHCP, no action is required.
To set a static IPv4 address, network mask, default gateway, and DNS server to the
bridge0
connection, enter:# nmcli connection modify bridge0 ipv4.addresses '192.0.2.1/24' ipv4.gateway '192.0.2.254' ipv4.dns '192.0.2.253' ipv4.dns-search 'example.com' ipv4.method manual
Configure the IPv6 settings:
To use this bridge device as a port of other devices, enter:
# nmcli connection modify bridge0 ipv6.method disabled
- To use stateless address autoconfiguration (SLAAC), no action is required.
To set a static IPv6 address, network mask, default gateway, and DNS server to the
bridge0
connection, enter:# nmcli connection modify bridge0 ipv6.addresses '2001:db8:1::1/64' ipv6.gateway '2001:db8:1::fffe' ipv6.dns '2001:db8:1::fffd' ipv6.dns-search 'example.com' ipv6.method manual
Optional: Configure further properties of the bridge. For example, to set the Spanning Tree Protocol (STP) priority of
bridge0
to16384
, enter:# nmcli connection modify bridge0 bridge.priority '16384'
By default, STP is enabled.
Activate the connection:
# nmcli connection up bridge0
Verify that the ports are connected, and the
CONNECTION
column displays the port’s connection name:# nmcli device DEVICE TYPE STATE CONNECTION ... enp7s0 ethernet connected bridge0-port1 enp8s0 ethernet connected bridge0-port2
When you activate any port of the connection, NetworkManager also activates the bridge, but not the other ports of it. You can configure that Red Hat Enterprise Linux enables all ports automatically when the bridge is enabled:
Enable the
connection.autoconnect-slaves
parameter of the bridge connection:# nmcli connection modify bridge0 connection.autoconnect-slaves 1
Reactivate the bridge:
# nmcli connection up bridge0
Verification
Use the
ip
utility to display the link status of Ethernet devices that are ports of a specific bridge:# ip link show master bridge0 3: enp7s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel master bridge0 state UP mode DEFAULT group default qlen 1000 link/ether 52:54:00:62:61:0e brd ff:ff:ff:ff:ff:ff 4: enp8s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel master bridge0 state UP mode DEFAULT group default qlen 1000 link/ether 52:54:00:9e:f1:ce brd ff:ff:ff:ff:ff:ff
Use the
bridge
utility to display the status of Ethernet devices that are ports of any bridge device:# bridge link show 3: enp7s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 master bridge0 state forwarding priority 32 cost 100 4: enp8s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 master bridge0 state listening priority 32 cost 100 5: enp9s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 master bridge1 state forwarding priority 32 cost 100 6: enp11s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 master bridge1 state blocking priority 32 cost 100 ...
To display the status for a specific Ethernet device, use the
bridge link show dev <ethernet_device_name>
command.
Additional resources
-
nm-settings(5)
man page -
bridge(8)
man page - NetworkManager duplicates a connection after restart of NetworkManager service
- How to configure a bridge with VLAN information?
6.2. Configuring a network bridge by using the RHEL web console
Use the RHEL web console to configure a network bridge if you prefer to manage network settings using a web browser-based interface.
Prerequisites
- Two or more physical or virtual network devices are installed on the server.
- To use Ethernet devices as ports of the bridge, the physical or virtual Ethernet devices must be installed on the server.
To use team, bond, or VLAN devices as ports of the bridge, you can either create these devices while you create the bridge or you can create them in advance as described in:
You have installed the RHEL 8 web console.
For instructions, see Installing and enabling the web console.
Procedure
Log in to the RHEL 8 web console.
For details, see Logging in to the web console.
- Select the Networking tab in the navigation on the left side of the screen.
- Click Interfaces section. in the
- Enter the name of the bridge device you want to create.
- Select the interfaces that should be ports of the bridge.
Optional: Enable the Spanning tree protocol (STP) feature to avoid bridge loops and broadcast radiation.
- Click .
By default, the bridge uses a dynamic IP address. If you want to set a static IP address:
- Click the name of the bridge in the Interfaces section.
- Click Edit next to the protocol you want to configure.
- Select Manual next to Addresses, and enter the IP address, prefix, and default gateway.
- In the DNS section, click the button, and enter the IP address of the DNS server. Repeat this step to set multiple DNS servers.
- In the DNS search domains section, click the button, and enter the search domain.
If the interface requires static routes, configure them in the Routes section.
- Click
Verification
Select the Networking tab in the navigation on the left side of the screen, and check if there is incoming and outgoing traffic on the interface:
6.3. Configuring a network bridge by using nmtui
The nmtui
application provides a text-based user interface for NetworkManager. You can use nmtui
to configure a network bridge on a host without a graphical interface.
In nmtui
:
- Navigate by using the cursor keys.
- Press a button by selecting it and hitting Enter.
- Select and clear checkboxes by using Space.
Prerequisites
- Two or more physical or virtual network devices are installed on the server.
- To use Ethernet devices as ports of the bridge, the physical or virtual Ethernet devices must be installed on the server.
Procedure
If you do not know the network device names on which you want configure a network bridge, display the available devices:
# nmcli device status DEVICE TYPE STATE CONNECTION enp7s0 ethernet unavailable -- enp8s0 ethernet unavailable -- ...
Start
nmtui
:# nmtui
-
Select
Edit a connection
, and press Enter. -
Press
Add
. -
Select
Bridge
from the list of network types, and press Enter. Optional: Enter a name for the NetworkManager profile to be created.
On hosts with multiple profiles, a meaningful name makes it easier to identify the purpose of a profile.
-
Enter the bridge device name to be created into the
Device
field. Add ports to the bridge to be created:
-
Press
Add
next to theSlaves
list. -
Select the type of the interface you want to add as port to the bridge, for example,
Ethernet
. - Optional: Enter a name for the NetworkManager profile to be created for this bridge port.
-
Enter the port’s device name into the
Device
field. Press
OK
to return to the window with the bridge settings.Figure 6.1. Adding an Ethernet device as port to a bridge
- Repeat these steps to add more ports to the bridge.
-
Press
Depending on your environment, configure the IP address settings in the
IPv4 configuration
andIPv6 configuration
areas accordingly. For this, press the button next to these areas, and select:-
Disabled
, if the bridge does not require an IP address. -
Automatic
, if a DHCP server or stateless address autoconfiguration (SLAAC) dynamically assigns an IP address to the bridge. Manual
, if the network requires static IP address settings. In this case, you must fill further fields:-
Press
Show
next to the protocol you want to configure to display additional fields. Press
Add
next toAddresses
, and enter the IP address and the subnet mask in Classless Inter-Domain Routing (CIDR) format.If you do not specify a subnet mask, NetworkManager sets a
/32
subnet mask for IPv4 addresses and/64
for IPv6 addresses.- Enter the address of the default gateway.
-
Press
Add
next toDNS servers
, and enter the DNS server address. -
Press
Add
next toSearch domains
, and enter the DNS search domain.
-
Press
Figure 6.2. Example of a bridge connection without IP address settings
-
-
Press
OK
to create and automatically activate the new connection. -
Press
Back
to return to the main menu. -
Select
Quit
, and press Enter to close thenmtui
application.
Verification
Use the
ip
utility to display the link status of Ethernet devices that are ports of a specific bridge:# ip link show master bridge0 3: enp7s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel master bridge0 state UP mode DEFAULT group default qlen 1000 link/ether 52:54:00:62:61:0e brd ff:ff:ff:ff:ff:ff 4: enp8s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel master bridge0 state UP mode DEFAULT group default qlen 1000 link/ether 52:54:00:9e:f1:ce brd ff:ff:ff:ff:ff:ff
Use the
bridge
utility to display the status of Ethernet devices that are ports of any bridge device:# bridge link show 3: enp7s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 master bridge0 state forwarding priority 32 cost 100 4: enp8s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 master bridge0 state listening priority 32 cost 100 ...
To display the status for a specific Ethernet device, use the
bridge link show dev <ethernet_device_name>
command.
6.4. Configuring a network bridge by using nm-connection-editor
If you use Red Hat Enterprise Linux with a graphical interface, you can configure network bridges using the nm-connection-editor
application.
Note that nm-connection-editor
can add only new ports to a bridge. To use an existing connection profile as a port, create the bridge using the nmcli
utility as described in Configuring a network bridge by using nmcli.
Prerequisites
- Two or more physical or virtual network devices are installed on the server.
- To use Ethernet devices as ports of the bridge, the physical or virtual Ethernet devices must be installed on the server.
- To use team, bond, or VLAN devices as ports of the bridge, ensure that these devices are not already configured.
Procedure
Open a terminal, and enter
nm-connection-editor
:$ nm-connection-editor
- Click the button to add a new connection.
- Select the Bridge connection type, and click .
On the Bridge tab:
- Optional: Set the name of the bridge interface in the Interface name field.
Click the
button to create a new connection profile for a network interface and adding the profile as a port to the bridge.- Select the connection type of the interface. For example, select Ethernet for a wired connection.
- Optional: Set a connection name for the port device.
- If you create a connection profile for an Ethernet device, open the Ethernet tab, and select in the Device field the network interface you want to add as a port to the bridge. If you selected a different device type, configure it accordingly.
- Click .
Repeat the previous step for each interface you want to add to the bridge.
- Optional: Configure further bridge settings, such as Spanning Tree Protocol (STP) options.
Configure the IP address settings on both the IPv4 Settings and IPv6 Settings tabs:
- To use this bridge device as a port of other devices, set the Method field to Disabled.
- To use DHCP, leave the Method field at its default, Automatic (DHCP).
To use static IP settings, set the Method field to Manual and fill the fields accordingly:
- Click .
-
Close
nm-connection-editor
.
Verification
Use the
ip
utility to display the link status of Ethernet devices that are ports of a specific bridge.# ip link show master bridge0 3: enp7s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel master bridge0 state UP mode DEFAULT group default qlen 1000 link/ether 52:54:00:62:61:0e brd ff:ff:ff:ff:ff:ff 4: enp8s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel master bridge0 state UP mode DEFAULT group default qlen 1000 link/ether 52:54:00:9e:f1:ce brd ff:ff:ff:ff:ff:ff
Use the
bridge
utility to display the status of Ethernet devices that are ports in any bridge device:# bridge link show 3: enp7s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 master bridge0 state forwarding priority 32 cost 100 4: enp8s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 master bridge0 state listening priority 32 cost 100 5: enp9s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 master bridge1 state forwarding priority 32 cost 100 6: enp11s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 master bridge1 state blocking priority 32 cost 100 ...
To display the status for a specific Ethernet device, use the
bridge link show dev ethernet_device_name
command.
Additional resources
- Configuring a network bond by using nm-connection-editor
- Configuring a network team by using nm-connection-editor
- Configuring VLAN tagging by using nm-connection-editor
- Configuring NetworkManager to avoid using a specific profile to provide a default gateway
- How to configure a bridge with VLAN information?
6.5. Configuring a network bridge by using nmstatectl
Use the nmstatectl
utility to configure a network bridge through the Nmstate API. The Nmstate API ensures that, after setting the configuration, the result matches the configuration file. If anything fails, nmstatectl
automatically rolls back the changes to avoid leaving the system in an incorrect state.
Depending on your environment, adjust the YAML file accordingly. For example, to use different devices than Ethernet adapters in the bridge, adapt the base-iface
attribute and type
attributes of the ports you use in the bridge.
Prerequisites
- Two or more physical or virtual network devices are installed on the server.
- To use Ethernet devices as ports in the bridge, the physical or virtual Ethernet devices must be installed on the server.
-
To use team, bond, or VLAN devices as ports in the bridge, set the interface name in the
port
list, and define the corresponding interfaces. -
The
nmstate
package is installed.
Procedure
Create a YAML file, for example
~/create-bridge.yml
, with the following content:--- interfaces: - name: bridge0 type: linux-bridge state: up ipv4: enabled: true address: - ip: 192.0.2.1 prefix-length: 24 dhcp: false ipv6: enabled: true address: - ip: 2001:db8:1::1 prefix-length: 64 autoconf: false dhcp: false bridge: options: stp: enabled: true port: - name: enp1s0 - name: enp7s0 - name: enp1s0 type: ethernet state: up - name: enp7s0 type: ethernet state: up routes: config: - destination: 0.0.0.0/0 next-hop-address: 192.0.2.254 next-hop-interface: bridge0 - destination: ::/0 next-hop-address: 2001:db8:1::fffe next-hop-interface: bridge0 dns-resolver: config: search: - example.com server: - 192.0.2.200 - 2001:db8:1::ffbb
These settings define a network bridge with the following settings:
-
Network interfaces in the bridge:
enp1s0
andenp7s0
- Spanning Tree Protocol (STP): Enabled
-
Static IPv4 address:
192.0.2.1
with the/24
subnet mask -
Static IPv6 address:
2001:db8:1::1
with the/64
subnet mask -
IPv4 default gateway:
192.0.2.254
-
IPv6 default gateway:
2001:db8:1::fffe
-
IPv4 DNS server:
192.0.2.200
-
IPv6 DNS server:
2001:db8:1::ffbb
-
DNS search domain:
example.com
-
Network interfaces in the bridge:
Apply the settings to the system:
# nmstatectl apply ~/create-bridge.yml
Verification
Display the status of the devices and connections:
# nmcli device status DEVICE TYPE STATE CONNECTION bridge0 bridge connected bridge0
Display all settings of the connection profile:
# nmcli connection show bridge0 connection.id: bridge0_ connection.uuid: e2cc9206-75a2-4622-89cf-1252926060a9 connection.stable-id: -- connection.type: bridge connection.interface-name: bridge0 ...
Display the connection settings in YAML format:
# nmstatectl show bridge0
Additional resources
-
nmstatectl(8)
man page -
/usr/share/doc/nmstate/examples/
directory - How to configure a bridge with VLAN information?
6.6. Configuring a network bridge by using the network
RHEL system role
You can connect multiple networks on layer 2 of the Open Systems Interconnection (OSI) model by creating a network bridge. To configure a bridge, create a connection profile in NetworkManager. By using Ansible and the network
RHEL system role, you can automate this process and remotely configure connection profiles on the hosts defined in a playbook.
You can use the network
RHEL system role to configure a bridge and, if a connection profile for the bridge’s parent device does not exists, the role can create it as well.
If you want to assign IP addresses, gateways, and DNS settings to a bridge, configure them on the bridge and not on its ports.
Prerequisites
- You have prepared the control node and the managed nodes
- You are logged in to the control node as a user who can run playbooks on the managed nodes.
-
The account you use to connect to the managed nodes has
sudo
permissions on them. - Two or more physical or virtual network devices are installed on the server.
Procedure
Create a playbook file, for example
~/playbook.yml
, with the following content:--- - name: Configure the network hosts: managed-node-01.example.com tasks: - name: Bridge connection profile with two Ethernet ports ansible.builtin.include_role: name: rhel-system-roles.network vars: network_connections: # Bridge profile - name: bridge0 type: bridge interface_name: bridge0 ip: dhcp4: yes auto6: yes state: up # Port profile for the 1st Ethernet device - name: bridge0-port1 interface_name: enp7s0 type: ethernet controller: bridge0 port_type: bridge state: up # Port profile for the 2nd Ethernet device - name: bridge0-port2 interface_name: enp8s0 type: ethernet controller: bridge0 port_type: bridge state: up
The settings specified in the example playbook include the following:
type: <profile_type>
- Sets the type of the profile to create. The example playbook creates three connection profiles: One for the bridge and two for the Ethernet devices.
dhcp4: yes
- Enables automatic IPv4 address assignment from DHCP, PPP, or similar services.
auto6: yes
-
Enables IPv6 auto-configuration. By default, NetworkManager uses Router Advertisements. If the router announces the
managed
flag, NetworkManager requests an IPv6 address and prefix from a DHCPv6 server.
For details about all variables used in the playbook, see the
/usr/share/ansible/roles/rhel-system-roles.network/README.md
file on the control node.Validate the playbook syntax:
$ ansible-playbook --syntax-check ~/playbook.yml
Note that this command only validates the syntax and does not protect against a wrong but valid configuration.
Run the playbook:
$ ansible-playbook ~/playbook.yml
Verification
Display the link status of Ethernet devices that are ports of a specific bridge:
# ansible managed-node-01.example.com -m command -a 'ip link show master bridge0' managed-node-01.example.com | CHANGED | rc=0 >> 3: enp7s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel master bridge0 state UP mode DEFAULT group default qlen 1000 link/ether 52:54:00:62:61:0e brd ff:ff:ff:ff:ff:ff 4: enp8s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel master bridge0 state UP mode DEFAULT group default qlen 1000 link/ether 52:54:00:9e:f1:ce brd ff:ff:ff:ff:ff:ff
Display the status of Ethernet devices that are ports of any bridge device:
# ansible managed-node-01.example.com -m command -a 'bridge link show' managed-node-01.example.com | CHANGED | rc=0 >> 3: enp7s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 master bridge0 state forwarding priority 32 cost 100 4: enp8s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 master bridge0 state listening priority 32 cost 100
Additional resources
-
/usr/share/ansible/roles/rhel-system-roles.network/README.md
file -
/usr/share/doc/rhel-system-roles/network/
directory
Chapter 7. Setting up an IPsec VPN
A virtual private network (VPN) is a way of connecting to a local network over the internet. IPsec
provided by Libreswan
is the preferred method for creating a VPN. Libreswan
is a user-space IPsec
implementation for VPN. A VPN enables the communication between your LAN, and another, remote LAN by setting up a tunnel across an intermediate network such as the internet. For security reasons, a VPN tunnel always uses authentication and encryption. For cryptographic operations, Libreswan
uses the NSS
library.
7.1. Configuring a VPN connection with control-center
If you use Red Hat Enterprise Linux with a graphical interface, you can configure a VPN connection in the GNOME control-center
.
Prerequisites
-
The
NetworkManager-libreswan-gnome
package is installed.
Procedure
-
Press the Super key, type
Settings
, and press Enter to open thecontrol-center
application. -
Select the
Network
entry on the left. - Click the + icon.
-
Select
VPN
. Select the
Identity
menu entry to see the basic configuration options:General
Gateway
— The name orIP
address of the remote VPN gateway.Authentication
Type
-
IKEv2 (Certificate)
- client is authenticated by certificate. It is more secure (default). IKEv1 (XAUTH)
- client is authenticated by user name and password, or a pre-shared key (PSK).The following configuration settings are available under the
Advanced
section:Figure 7.1. Advanced options of a VPN connection
WarningWhen configuring an IPsec-based VPN connection using the
gnome-control-center
application, theAdvanced
dialog displays the configuration, but it does not allow any changes. As a consequence, users cannot change any advanced IPsec options. Use thenm-connection-editor
ornmcli
tools instead to perform configuration of the advanced properties.Identification
Domain
— If required, enter the Domain Name.Security
-
Phase1 Algorithms
— corresponds to theike
Libreswan parameter — enter the algorithms to be used to authenticate and set up an encrypted channel. Phase2 Algorithms
— corresponds to theesp
Libreswan parameter — enter the algorithms to be used for theIPsec
negotiations.Check the
Disable PFS
field to turn off Perfect Forward Secrecy (PFS) to ensure compatibility with old servers that do not support PFS.-
Phase1 Lifetime
— corresponds to theikelifetime
Libreswan parameter — how long the key used to encrypt the traffic will be valid. Phase2 Lifetime
— corresponds to thesalifetime
Libreswan parameter — how long a particular instance of a connection should last before expiring.Note that the encryption key should be changed from time to time for security reasons.
Remote network
— corresponds to therightsubnet
Libreswan parameter — the destination private remote network that should be reached through the VPN.Check the
narrowing
field to enable narrowing. Note that it is only effective in IKEv2 negotiation.-
Enable fragmentation
— corresponds to thefragmentation
Libreswan parameter — whether or not to allow IKE fragmentation. Valid values areyes
(default) orno
. -
Enable Mobike
— corresponds to themobike
Libreswan parameter — whether to allow Mobility and Multihoming Protocol (MOBIKE, RFC 4555) to enable a connection to migrate its endpoint without needing to restart the connection from scratch. This is used on mobile devices that switch between wired, wireless, or mobile data connections. The values areno
(default) oryes
.
-
Select the
menu entry:IPv4 Method
-
Automatic (DHCP)
— Choose this option if the network you are connecting to uses aDHCP
server to assign dynamicIP
addresses. -
Link-Local Only
— Choose this option if the network you are connecting to does not have aDHCP
server and you do not want to assignIP
addresses manually. Random addresses will be assigned as per RFC 3927 with prefix169.254/16
. -
Manual
— Choose this option if you want to assignIP
addresses manually. Disable
—IPv4
is disabled for this connection.DNS
In the
DNS
section, whenAutomatic
isON
, switch it toOFF
to enter the IP address of a DNS server you want to use separating the IPs by comma.Routes
Note that in the
Routes
section, whenAutomatic
isON
, routes from DHCP are used, but you can also add additional static routes. WhenOFF
, only static routes are used.-
Address
— Enter theIP
address of a remote network or host. -
Netmask
— The netmask or prefix length of theIP
address entered above. -
Gateway
— TheIP
address of the gateway leading to the remote network or host entered above. Metric
— A network cost, a preference value to give to this route. Lower values will be preferred over higher values.Use this connection only for resources on its network
Select this check box to prevent the connection from becoming the default route. Selecting this option means that only traffic specifically destined for routes learned automatically over the connection or entered here manually is routed over the connection.
-
To configure
IPv6
settings in aVPN
connection, select the menu entry:IPv6 Method
-
Automatic
— Choose this option to useIPv6
Stateless Address AutoConfiguration (SLAAC) to create an automatic, stateless configuration based on the hardware address and Router Advertisements (RA). -
Automatic, DHCP only
— Choose this option to not use RA, but request information fromDHCPv6
directly to create a stateful configuration. -
Link-Local Only
— Choose this option if the network you are connecting to does not have aDHCP
server and you do not want to assignIP
addresses manually. Random addresses will be assigned as per RFC 4862 with prefixFE80::0
. -
Manual
— Choose this option if you want to assignIP
addresses manually. Disable
—IPv6
is disabled for this connection.Note that
DNS
,Routes
,Use this connection only for resources on its network
are common toIPv4
settings.
-
-
Once you have finished editing the
VPN
connection, click the button to customize the configuration or the button to save it for the existing one. -
Switch the profile to
ON
to active theVPN
connection.
Additional resources
-
nm-settings-libreswan(5)
7.2. Configuring a VPN connection using nm-connection-editor
If you use Red Hat Enterprise Linux with a graphical interface, you can configure a VPN connection in the nm-connection-editor
application.
Prerequisites
-
The
NetworkManager-libreswan-gnome
package is installed. If you configure an Internet Key Exchange version 2 (IKEv2) connection:
- The certificate is imported into the IPsec network security services (NSS) database.
- The nickname of the certificate in the NSS database is known.
Procedure
Open a terminal, and enter:
$ nm-connection-editor
- Click the button to add a new connection.
-
Select the
IPsec based VPN
connection type, and click . On the
VPN
tab:Enter the host name or IP address of the VPN gateway into the
Gateway
field, and select an authentication type. Based on the authentication type, you must enter different additional information:-
IKEv2 (Certifiate)
authenticates the client by using a certificate, which is more secure. This setting requires the nickname of the certificate in the IPsec NSS database IKEv1 (XAUTH)
authenticates the user by using a user name and password (pre-shared key). This setting requires that you enter the following values:- User name
- Password
- Group name
- Secret
-
If the remote server specifies a local identifier for the IKE exchange, enter the exact string in the
Remote ID
field. In the remote server runs Libreswan, this value is set in the server’sleftid
parameter.Optional: Configure additional settings by clicking the
button. You can configure the following settings:Identification
-
Domain
— If required, enter the domain name.
-
Security
-
Phase1 Algorithms
corresponds to theike
Libreswan parameter. Enter the algorithms to be used to authenticate and set up an encrypted channel. Phase2 Algorithms
corresponds to theesp
Libreswan parameter. Enter the algorithms to be used for theIPsec
negotiations.Check the
Disable PFS
field to turn off Perfect Forward Secrecy (PFS) to ensure compatibility with old servers that do not support PFS.-
Phase1 Lifetime
corresponds to theikelifetime
Libreswan parameter. This parameter defines how long the key used to encrypt the traffic is valid. -
Phase2 Lifetime
corresponds to thesalifetime
Libreswan parameter. This parameter defines how long a security association is valid.
-
Connectivity
Remote network
corresponds to therightsubnet
Libreswan parameter and defines the destination private remote network that should be reached through the VPN.Check the
narrowing
field to enable narrowing. Note that it is only effective in the IKEv2 negotiation.-
Enable fragmentation
corresponds to thefragmentation
Libreswan parameter and defines whether or not to allow IKE fragmentation. Valid values areyes
(default) orno
. -
Enable Mobike
corresponds to themobike
Libreswan parameter. The parameter defines whether to allow Mobility and Multihoming Protocol (MOBIKE) (RFC 4555) to enable a connection to migrate its endpoint without needing to restart the connection from scratch. This is used on mobile devices that switch between wired, wireless or mobile data connections. The values areno
(default) oryes
.
On the
IPv4 Settings
tab, select the IP assignment method and, optionally, set additional static addresses, DNS servers, search domains, and routes.- Save the connection.
-
Close
nm-connection-editor
.
When you add a new connection by clicking the NetworkManager creates a new configuration file for that connection and then opens the same dialog that is used for editing an existing connection. The difference between these dialogs is that an existing connection profile has a Details menu entry.
button,Additional resources
-
nm-settings-libreswan(5)
man page
7.3. Configuring automatic detection and usage of ESP hardware offload to accelerate an IPsec connection
Offloading Encapsulating Security Payload (ESP) to the hardware accelerates IPsec connections over Ethernet. By default, Libreswan detects if hardware supports this feature and, as a result, enables ESP hardware offload. In case that the feature was disabled or explicitly enabled, you can switch back to automatic detection.
Prerequisites
- The network card supports ESP hardware offload.
- The network driver supports ESP hardware offload.
- The IPsec connection is configured and works.
Procedure
-
Edit the Libreswan configuration file in the
/etc/ipsec.d/
directory of the connection that should use automatic detection of ESP hardware offload support. -
Ensure the
nic-offload
parameter is not set in the connection’s settings. If you removed
nic-offload
, restart theipsec
service:# systemctl restart ipsec
Verification
Display the
tx_ipsec
andrx_ipsec
counters of the Ethernet device the IPsec connection uses:# ethtool -S enp1s0 | egrep "_ipsec" tx_ipsec: 10 rx_ipsec: 10
Send traffic through the IPsec tunnel. For example, ping a remote IP address:
# ping -c 5 remote_ip_address
Display the
tx_ipsec
andrx_ipsec
counters of the Ethernet device again:# ethtool -S enp1s0 | egrep "_ipsec" tx_ipsec: 15 rx_ipsec: 15
If the counter values have increased, ESP hardware offload works.
Additional resources
7.4. Configuring ESP hardware offload on a bond to accelerate an IPsec connection
Offloading Encapsulating Security Payload (ESP) to the hardware accelerates IPsec connections. If you use a network bond for fail-over reasons, the requirements and the procedure to configure ESP hardware offload are different from those using a regular Ethernet device. For example, in this scenario, you enable the offload support on the bond, and the kernel applies the settings to the ports of the bond.
Prerequisites
- All network cards in the bond support ESP hardware offload.
-
The network driver supports ESP hardware offload on a bond device. In RHEL, only the
ixgbe
driver supports this feature. - The bond is configured and works.
-
The bond uses the
active-backup
mode. The bonding driver does not support any other modes for this feature. - The IPsec connection is configured and works.
Procedure
Enable ESP hardware offload support on the network bond:
# nmcli connection modify bond0 ethtool.feature-esp-hw-offload on
This command enables ESP hardware offload support on the
bond0
connection.Reactivate the
bond0
connection:# nmcli connection up bond0
Edit the Libreswan configuration file in the
/etc/ipsec.d/
directory of the connection that should use ESP hardware offload, and append thenic-offload=yes
statement to the connection entry:conn example ... nic-offload=yes
Restart the
ipsec
service:# systemctl restart ipsec
Verification
Display the active port of the bond:
# grep "Currently Active Slave" /proc/net/bonding/bond0 Currently Active Slave: enp1s0
Display the
tx_ipsec
andrx_ipsec
counters of the active port:# ethtool -S enp1s0 | egrep "_ipsec" tx_ipsec: 10 rx_ipsec: 10
Send traffic through the IPsec tunnel. For example, ping a remote IP address:
# ping -c 5 remote_ip_address
Display the
tx_ipsec
andrx_ipsec
counters of the active port again:# ethtool -S enp1s0 | egrep "_ipsec" tx_ipsec: 15 rx_ipsec: 15
If the counter values have increased, ESP hardware offload works.
Additional resources
- Configuring a network bond
- Configuring a VPN with IPsec section in the Securing networks document
Chapter 8. Configuring IP tunnels
Similar to a VPN, an IP tunnel directly connects two networks over a third network, such as the internet. However, not all tunnel protocols support encryption.
The routers in both networks that establish the tunnel requires at least two interfaces:
- One interface that is connected to the local network
- One interface that is connected to the network through which the tunnel is established.
To establish the tunnel, you create a virtual interface on both routers with an IP address from the remote subnet.
NetworkManager supports the following IP tunnels:
- Generic Routing Encapsulation (GRE)
- Generic Routing Encapsulation over IPv6 (IP6GRE)
- Generic Routing Encapsulation Terminal Access Point (GRETAP)
- Generic Routing Encapsulation Terminal Access Point over IPv6 (IP6GRETAP)
- IPv4 over IPv4 (IPIP)
- IPv4 over IPv6 (IPIP6)
- IPv6 over IPv6 (IP6IP6)
- Simple Internet Transition (SIT)
Depending on the type, these tunnels act either on layer 2 or 3 of the Open Systems Interconnection (OSI) model.
8.1. Configuring an IPIP tunnel to encapsulate IPv4 traffic in IPv4 packets
An IP over IP (IPIP) tunnel operates on OSI layer 3 and encapsulates IPv4 traffic in IPv4 packets as described in RFC 2003.
Data sent through an IPIP tunnel is not encrypted. For security reasons, use the tunnel only for data that is already encrypted, for example, by other protocols, such as HTTPS.
Note that IPIP tunnels support only unicast packets. If you require an IPv4 tunnel that supports multicast, see Configuring a GRE tunnel to encapsulate layer-3 traffic in IPv4 packets.
For example, you can create an IPIP tunnel between two RHEL routers to connect two internal subnets over the internet as shown in the following diagram:
![IPIP tunnel](https://access.redhat.com/webassets/avalon/d/Red_Hat_Enterprise_Linux-8-Configuring_and_managing_networking-en-US/images/7a4baade335da7cdc9159871199529bb/IPIP-tunnel.png)
Prerequisites
- Each RHEL router has a network interface that is connected to its local subnet.
- Each RHEL router has a network interface that is connected to the internet.
- The traffic you want to send through the tunnel is IPv4 unicast.
Procedure
On the RHEL router in network A:
Create an IPIP tunnel interface named
tun0
:# nmcli connection add type ip-tunnel ip-tunnel.mode ipip con-name tun0 ifname tun0 remote 198.51.100.5 local 203.0.113.10
The
remote
andlocal
parameters set the public IP addresses of the remote and the local routers.Set the IPv4 address to the
tun0
device:# nmcli connection modify tun0 ipv4.addresses '10.0.1.1/30'
Note that a
/30
subnet with two usable IP addresses is sufficient for the tunnel.Configure the
tun0
connection to use a manual IPv4 configuration:# nmcli connection modify tun0 ipv4.method manual
Add a static route that routes traffic to the
172.16.0.0/24
network to the tunnel IP on router B:# nmcli connection modify tun0 +ipv4.routes "172.16.0.0/24 10.0.1.2"
Enable the
tun0
connection.# nmcli connection up tun0
Enable packet forwarding:
# echo "net.ipv4.ip_forward=1" > /etc/sysctl.d/95-IPv4-forwarding.conf # sysctl -p /etc/sysctl.d/95-IPv4-forwarding.conf
On the RHEL router in network B:
Create an IPIP tunnel interface named
tun0
:# nmcli connection add type ip-tunnel ip-tunnel.mode ipip con-name tun0 ifname tun0 remote 203.0.113.10 local 198.51.100.5
The
remote
andlocal
parameters set the public IP addresses of the remote and local routers.Set the IPv4 address to the
tun0
device:# nmcli connection modify tun0 ipv4.addresses '10.0.1.2/30'
Configure the
tun0
connection to use a manual IPv4 configuration:# nmcli connection modify tun0 ipv4.method manual
Add a static route that routes traffic to the
192.0.2.0/24
network to the tunnel IP on router A:# nmcli connection modify tun0 +ipv4.routes "192.0.2.0/24 10.0.1.1"
Enable the
tun0
connection.# nmcli connection up tun0
Enable packet forwarding:
# echo "net.ipv4.ip_forward=1" > /etc/sysctl.d/95-IPv4-forwarding.conf # sysctl -p /etc/sysctl.d/95-IPv4-forwarding.conf
Verification
From each RHEL router, ping the IP address of the internal interface of the other router:
On Router A, ping
172.16.0.1
:# ping 172.16.0.1
On Router B, ping
192.0.2.1
:# ping 192.0.2.1
8.2. Configuring a GRE tunnel to encapsulate layer-3 traffic in IPv4 packets
A Generic Routing Encapsulation (GRE) tunnel encapsulates layer-3 traffic in IPv4 packets as described in RFC 2784. A GRE tunnel can encapsulate any layer 3 protocol with a valid Ethernet type.
Data sent through a GRE tunnel is not encrypted. For security reasons, use the tunnel only for data that is already encrypted, for example, by other protocols, such as HTTPS.
For example, you can create a GRE tunnel between two RHEL routers to connect two internal subnets over the internet as shown in the following diagram:
![GRE tunnel](https://access.redhat.com/webassets/avalon/d/Red_Hat_Enterprise_Linux-8-Configuring_and_managing_networking-en-US/images/ee24ab1cb16aa24353c8a2fd6fbbb556/GRE-tunnel.png)
Prerequisites
- Each RHEL router has a network interface that is connected to its local subnet.
- Each RHEL router has a network interface that is connected to the internet.
Procedure
On the RHEL router in network A:
Create a GRE tunnel interface named
gre1
:# nmcli connection add type ip-tunnel ip-tunnel.mode gre con-name gre1 ifname gre1 remote 198.51.100.5 local 203.0.113.10
The
remote
andlocal
parameters set the public IP addresses of the remote and the local routers.ImportantThe
gre0
device name is reserved. Usegre1
or a different name for the device.Set the IPv4 address to the
gre1
device:# nmcli connection modify gre1 ipv4.addresses '10.0.1.1/30'
Note that a
/30
subnet with two usable IP addresses is sufficient for the tunnel.Configure the
gre1
connection to use a manual IPv4 configuration:# nmcli connection modify gre1 ipv4.method manual
Add a static route that routes traffic to the
172.16.0.0/24
network to the tunnel IP on router B:# nmcli connection modify gre1 +ipv4.routes "172.16.0.0/24 10.0.1.2"
Enable the
gre1
connection.# nmcli connection up gre1
Enable packet forwarding:
# echo "net.ipv4.ip_forward=1" > /etc/sysctl.d/95-IPv4-forwarding.conf # sysctl -p /etc/sysctl.d/95-IPv4-forwarding.conf
On the RHEL router in network B:
Create a GRE tunnel interface named
gre1
:# nmcli connection add type ip-tunnel ip-tunnel.mode gre con-name gre1 ifname gre1 remote 203.0.113.10 local 198.51.100.5
The
remote
andlocal
parameters set the public IP addresses of the remote and the local routers.Set the IPv4 address to the
gre1
device:# nmcli connection modify gre1 ipv4.addresses '10.0.1.2/30'
Configure the
gre1
connection to use a manual IPv4 configuration:# nmcli connection modify gre1 ipv4.method manual
Add a static route that routes traffic to the
192.0.2.0/24
network to the tunnel IP on router A:# nmcli connection modify gre1 +ipv4.routes "192.0.2.0/24 10.0.1.1"
Enable the
gre1
connection.# nmcli connection up gre1
Enable packet forwarding:
# echo "net.ipv4.ip_forward=1" > /etc/sysctl.d/95-IPv4-forwarding.conf # sysctl -p /etc/sysctl.d/95-IPv4-forwarding.conf
Verification
From each RHEL router, ping the IP address of the internal interface of the other router:
On Router A, ping
172.16.0.1
:# ping 172.16.0.1
On Router B, ping
192.0.2.1
:# ping 192.0.2.1
8.3. Configuring a GRETAP tunnel to transfer Ethernet frames over IPv4
A Generic Routing Encapsulation Terminal Access Point (GRETAP) tunnel operates on OSI level 2 and encapsulates Ethernet traffic in IPv4 packets as described in RFC 2784.
Data sent through a GRETAP tunnel is not encrypted. For security reasons, establish the tunnel over a VPN or a different encrypted connection.
For example, you can create a GRETAP tunnel between two RHEL routers to connect two networks using a bridge as shown in the following diagram:
![GRETAP tunnel](https://access.redhat.com/webassets/avalon/d/Red_Hat_Enterprise_Linux-8-Configuring_and_managing_networking-en-US/images/00b6e5003f5f139db0b0f35dfd051213/GRETAP-tunnel.png)
Prerequisites
- Each RHEL router has a network interface that is connected to its local network, and the interface has no IP configuration assigned.
- Each RHEL router has a network interface that is connected to the internet.
Procedure
On the RHEL router in network A:
Create a bridge interface named
bridge0
:# nmcli connection add type bridge con-name bridge0 ifname bridge0
Configure the IP settings of the bridge:
# nmcli connection modify bridge0 ipv4.addresses '192.0.2.1/24' # nmcli connection modify bridge0 ipv4.method manual
Add a new connection profile for the interface that is connected to local network to the bridge:
# nmcli connection add type ethernet slave-type bridge con-name bridge0-port1 ifname enp1s0 master bridge0
Add a new connection profile for the GRETAP tunnel interface to the bridge:
# nmcli connection add type ip-tunnel ip-tunnel.mode gretap slave-type bridge con-name bridge0-port2 ifname gretap1 remote 198.51.100.5 local 203.0.113.10 master bridge0
The
remote
andlocal
parameters set the public IP addresses of the remote and the local routers.ImportantThe
gretap0
device name is reserved. Usegretap1
or a different name for the device.Optional: Disable the Spanning Tree Protocol (STP) if you do not need it:
# nmcli connection modify bridge0 bridge.stp no
By default, STP is enabled and causes a delay before you can use the connection.
Configure that activating the
bridge0
connection automatically activates the ports of the bridge:# nmcli connection modify bridge0 connection.autoconnect-slaves 1
Active the
bridge0
connection:# nmcli connection up bridge0
On the RHEL router in network B:
Create a bridge interface named
bridge0
:# nmcli connection add type bridge con-name bridge0 ifname bridge0
Configure the IP settings of the bridge:
# nmcli connection modify bridge0 ipv4.addresses '192.0.2.2/24' # nmcli connection modify bridge0 ipv4.method manual
Add a new connection profile for the interface that is connected to local network to the bridge:
# nmcli connection add type ethernet slave-type bridge con-name bridge0-port1 ifname enp1s0 master bridge0
Add a new connection profile for the GRETAP tunnel interface to the bridge:
# nmcli connection add type ip-tunnel ip-tunnel.mode gretap slave-type bridge con-name bridge0-port2 ifname gretap1 remote 203.0.113.10 local 198.51.100.5 master bridge0
The
remote
andlocal
parameters set the public IP addresses of the remote and the local routers.Optional: Disable the Spanning Tree Protocol (STP) if you do not need it:
# nmcli connection modify bridge0 bridge.stp no
Configure that activating the
bridge0
connection automatically activates the ports of the bridge:# nmcli connection modify bridge0 connection.autoconnect-slaves 1
Active the
bridge0
connection:# nmcli connection up bridge0
Verification
On both routers, verify that the
enp1s0
andgretap1
connections are connected and that theCONNECTION
column displays the connection name of the port:# nmcli device nmcli device DEVICE TYPE STATE CONNECTION ... bridge0 bridge connected bridge0 enp1s0 ethernet connected bridge0-port1 gretap1 iptunnel connected bridge0-port2
From each RHEL router, ping the IP address of the internal interface of the other router:
On Router A, ping
192.0.2.2
:# ping 192.0.2.2
On Router B, ping
192.0.2.1
:# ping 192.0.2.1
Chapter 9. Using a VXLAN to create a virtual layer-2 domain for VMs
A virtual extensible LAN (VXLAN) is a networking protocol that tunnels layer-2 traffic over an IP network using the UDP protocol. For example, certain virtual machines (VMs), that are running on different hosts can communicate over a VXLAN tunnel. The hosts can be in different subnets or even in different data centers around the world. From the perspective of the VMs, other VMs in the same VXLAN are within the same layer-2 domain:
![vxlan tunnel](https://access.redhat.com/webassets/avalon/d/Red_Hat_Enterprise_Linux-8-Configuring_and_managing_networking-en-US/images/f0ed0f273b7b4b9f8ed9ab229efc49fd/vxlan-tunnel.png)
In this example, RHEL-host-A and RHEL-host-B use a bridge, br0
, to connect the virtual network of a VM on each host with a VXLAN named vxlan10
. Due to this configuration, the VXLAN is invisible to the VMs, and the VMs do not require any special configuration. If you later connect more VMs to the same virtual network, the VMs are automatically members of the same virtual layer-2 domain.
Just as normal layer-2 traffic, data in a VXLAN is not encrypted. For security reasons, use a VXLAN over a VPN or other types of encrypted connections.
9.1. Benefits of VXLANs
A virtual extensible LAN (VXLAN) provides the following major benefits:
- VXLANs use a 24-bit ID. Therefore, you can create up to 16,777,216 isolated networks. For example, a virtual LAN (VLAN), supports only 4,096 isolated networks.
- VXLANs use the IP protocol. This enables you to route the traffic and virtually run systems in different networks and locations within the same layer-2 domain.
- Unlike most tunnel protocols, a VXLAN is not only a point-to-point network. A VXLAN can learn the IP addresses of the other endpoints either dynamically or use statically-configured forwarding entries.
- Certain network cards support UDP tunnel-related offload features.
Additional resources
-
/usr/share/doc/kernel-doc-<kernel_version>/Documentation/networking/vxlan.rst
provided by thekernel-doc
package
9.2. Configuring the Ethernet interface on the hosts
To connect a RHEL VM host to the Ethernet, create a network connection profile, configure the IP settings, and activate the profile.
Run this procedure on both RHEL hosts, and adjust the IP address configuration accordingly.
Prerequisites
- The host is connected to the Ethernet.
Procedure
Add a new Ethernet connection profile to NetworkManager:
# nmcli connection add con-name Example ifname enp1s0 type ethernet
Configure the IPv4 settings:
# nmcli connection modify Example ipv4.addresses 198.51.100.2/24 ipv4.method manual ipv4.gateway 198.51.100.254 ipv4.dns 198.51.100.200 ipv4.dns-search example.com
Skip this step if the network uses DHCP.
Activate the
Example
connection:# nmcli connection up Example
Verification
Display the status of the devices and connections:
# nmcli device status DEVICE TYPE STATE CONNECTION enp1s0 ethernet connected Example
Ping a host in a remote network to verify the IP settings:
# ping RHEL-host-B.example.com
Note that you cannot ping the other VM host before you have configured the network on that host as well.
Additional resources
-
nm-settings(5)
man page
9.3. Creating a network bridge with a VXLAN attached
To make a virtual extensible LAN (VXLAN) invisible to virtual machines (VMs), create a bridge on a host, and attach the VXLAN to the bridge. Use NetworkManager to create both the bridge and the VXLAN. You do not add any traffic access point (TAP) devices of the VMs, typically named vnet*
on the host, to the bridge. The libvirtd
service adds them dynamically when the VMs start.
Run this procedure on both RHEL hosts, and adjust the IP addresses accordingly.
Procedure
Create the bridge
br0
:# nmcli connection add type bridge con-name br0 ifname br0 ipv4.method disabled ipv6.method disabled
This command sets no IPv4 and IPv6 addresses on the bridge device, because this bridge works on layer 2.
Create the VXLAN interface and attach it to
br0
:# nmcli connection add type vxlan slave-type bridge con-name br0-vxlan10 ifname vxlan10 id 10 local 198.51.100.2 remote 203.0.113.1 master br0
This command uses the following settings:
-
id 10
: Sets the VXLAN identifier. -
local 198.51.100.2
: Sets the source IP address of outgoing packets. -
remote 203.0.113.1
: Sets the unicast or multicast IP address to use in outgoing packets when the destination link layer address is not known in the VXLAN device forwarding database. -
master br0
: Sets this VXLAN connection to be created as a port in thebr0
connection. -
ipv4.method disabled
andipv6.method disabled
: Disables IPv4 and IPv6 on the bridge.
By default, NetworkManager uses
8472
as the destination port. If the destination port is different, additionally, pass thedestination-port <port_number>
option to the command.-
Activate the
br0
connection profile:# nmcli connection up br0
Open port
8472
for incoming UDP connections in the local firewall:# firewall-cmd --permanent --add-port=8472/udp # firewall-cmd --reload
Verification
Display the forwarding table:
# bridge fdb show dev vxlan10 2a:53:bd:d5:b3:0a master br0 permanent 00:00:00:00:00:00 dst 203.0.113.1 self permanent ...
Additional resources
-
nm-settings(5)
man page
9.4. Creating a virtual network in libvirt with an existing bridge
To enable virtual machines (VM) to use the br0
bridge with the attached virtual extensible LAN (VXLAN), first add a virtual network to the libvirtd
service that uses this bridge.
Prerequisites
-
You installed the
libvirt
package. -
You started and enabled the
libvirtd
service. -
You configured the
br0
device with the VXLAN on RHEL.
Procedure
Create the
~/vxlan10-bridge.xml
file with the following content:<network> <name>vxlan10-bridge</name> <forward mode="bridge" /> <bridge name="br0" /> </network>
Use the
~/vxlan10-bridge.xml
file to create a new virtual network inlibvirt
:# virsh net-define ~/vxlan10-bridge.xml
Remove the
~/vxlan10-bridge.xml
file:# rm ~/vxlan10-bridge.xml
Start the
vxlan10-bridge
virtual network:# virsh net-start vxlan10-bridge
Configure the
vxlan10-bridge
virtual network to start automatically when thelibvirtd
service starts:# virsh net-autostart vxlan10-bridge
Verification
Display the list of virtual networks:
# virsh net-list Name State Autostart Persistent ---------------------------------------------------- vxlan10-bridge active yes yes ...
Additional resources
-
virsh(1)
man page
9.5. Configuring virtual machines to use VXLAN
To configure a VM to use a bridge device with an attached virtual extensible LAN (VXLAN) on the host, create a new VM that uses the vxlan10-bridge
virtual network or update the settings of existing VMs to use this network.
Perform this procedure on the RHEL hosts.
Prerequisites
-
You configured the
vxlan10-bridge
virtual network inlibvirtd
.
Procedure
To create a new VM and configure it to use the
vxlan10-bridge
network, pass the--network network:vxlan10-bridge
option to thevirt-install
command when you create the VM:# virt-install ... --network network:vxlan10-bridge
To change the network settings of an existing VM:
Connect the VM’s network interface to the
vxlan10-bridge
virtual network:# virt-xml VM_name --edit --network network=vxlan10-bridge
Shut down the VM, and start it again:
# virsh shutdown VM_name # virsh start VM_name
Verification
Display the virtual network interfaces of the VM on the host:
# virsh domiflist VM_name Interface Type Source Model MAC ------------------------------------------------------------------- vnet1 bridge vxlan10-bridge virtio 52:54:00:c5:98:1c
Display the interfaces attached to the
vxlan10-bridge
bridge:# ip link show master vxlan10-bridge 18: vxlan10: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue master br0 state UNKNOWN mode DEFAULT group default qlen 1000 link/ether 2a:53:bd:d5:b3:0a brd ff:ff:ff:ff:ff:ff 19: vnet1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue master br0 state UNKNOWN mode DEFAULT group default qlen 1000 link/ether 52:54:00:c5:98:1c brd ff:ff:ff:ff:ff:ff
Note that the
libvirtd
service dynamically updates the bridge’s configuration. When you start a VM which uses thevxlan10-bridge
network, the correspondingvnet*
device on the host appears as a port of the bridge.Use address resolution protocol (ARP) requests to verify whether VMs are in the same VXLAN:
- Start two or more VMs in the same VXLAN.
Send an ARP request from one VM to the other one:
# arping -c 1 192.0.2.2 ARPING 192.0.2.2 from 192.0.2.1 enp1s0 Unicast reply from 192.0.2.2 [52:54:00:c5:98:1c] 1.450ms Sent 1 probe(s) (0 broadcast(s)) Received 1 response(s) (0 request(s), 0 broadcast(s))
If the command shows a reply, the VM is in the same layer-2 domain and, in this case in the same VXLAN.
Install the
iputils
package to use thearping
utility.
Additional resources
-
virt-install(1)
man page -
virt-xml(1)
man page -
virsh(1)
man page -
arping(8)
man page
Chapter 10. Managing wifi connections
RHEL provides multiple utilities and applications to configure and connect to wifi networks, for example:
-
Use the
nmcli
utility to configure connections by using the command line. -
Use the
nmtui
application to configure connections in a text-based user interface. - Use the GNOME system menu to quickly connect to wifi networks that do not require any configuration.
-
Use the
GNOME Settings
application to configure connections by using the GNOME application. -
Use the
nm-connection-editor
application to configure connections in a graphical user interface. -
Use the
network
RHEL system role to automate the configuration of connections on one or multiple hosts.
10.1. Supported wifi security types
Depending on the security type a wifi network supports, you can transmitted data more or less securely.
Do not connect to wifi networks that do not use encryption or which support only the insecure WEP or WPA standards.
RHEL 8 supports the following wifi security types:
-
None
: Encryption is disabled, and data is transferred in plain text over the network. -
Enhanced Open
: With opportunistic wireless encryption (OWE), devices negotiate unique pairwise master keys (PMK) to encrypt connections in wireless networks without authentication. -
WEP 40/128-bit Key (Hex or ASCII)
: The Wired Equivalent Privacy (WEP) protocol in this mode uses pre-shared keys only in hex or ASCII format. WEP is deprecated and will be removed in RHEL 9.1. -
WEP 128-bit Passphrase
. The WEP protocol in this mode uses an MD5 hash of the passphrase to derive a WEP key. WEP is deprecated and will be removed in RHEL 9.1. -
Dynamic WEP (802.1x)
: A combination of 802.1X and EAP that uses the WEP protocol with dynamic keys. WEP is deprecated and will be removed in RHEL 9.1. -
LEAP
: The Lightweight Extensible Authentication Protocol, which was developed by Cisco, is a proprietary version of the extensible authentication protocol (EAP). -
WPA & WPA2 Personal
: In personal mode, the Wi-Fi Protected Access (WPA) and Wi-Fi Protected Access 2 (WPA2) authentication methods use a pre-shared key. -
WPA & WPA2 Enterprise
: In enterprise mode, WPA and WPA2 use the EAP framework and authenticate users to a remote authentication dial-in user service (RADIUS) server. -
WPA3 Personal
: Wi-Fi Protected Access 3 (WPA3) Personal uses simultaneous authentication of equals (SAE) instead of pre-shared keys (PSK) to prevent dictionary attacks. WPA3 uses perfect forward secrecy (PFS).
10.2. Connecting to a wifi network by using nmcli
You can use the nmcli
utility to connect to a wifi network. When you attempt to connect to a network for the first time, the utility automatically creates a NetworkManager connection profile for it. If the network requires additional settings, such as static IP addresses, you can then modify the profile after it has been automatically created.
Prerequisites
- A wifi device is installed on the host.
- The wifi device is enabled, if it has a hardware switch.
Procedure
If the wifi radio has been disabled in NetworkManager, enable this feature:
# nmcli radio wifi on
Optional: Display the available wifi networks:
# nmcli device wifi list IN-USE BSSID SSID MODE CHAN RATE SIGNAL BARS SECURITY 00:53:00:2F:3B:08 Office Infra 44 270 Mbit/s 57 ▂▄▆_ WPA2 WPA3 00:53:00:15:03:BF -- Infra 1 130 Mbit/s 48 ▂▄__ WPA2 WPA3
The service set identifier (
SSID
) column contains the names of the networks. If the column shows--
, the access point of this network does not broadcast an SSID.Connect to the wifi network:
# nmcli device wifi connect Office --ask Password: wifi-password
If you prefer to set the password in the command instead of entering it interactively, use the
password wifi-password
option in the command instead of--ask
:# nmcli device wifi connect Office wifi-password
Note that, if the network requires static IP addresses, NetworkManager fails to activate the connection at this point. You can configure the IP addresses in later steps.
If the network requires static IP addresses:
Configure the IPv4 address settings, for example:
# nmcli connection modify Office ipv4.method manual ipv4.addresses 192.0.2.1/24 ipv4.gateway 192.0.2.254 ipv4.dns 192.0.2.200 ipv4.dns-search example.com
Configure the IPv6 address settings, for example:
# nmcli connection modify Office ipv6.method manual ipv6.addresses 2001:db8:1::1/64 ipv6.gateway 2001:db8:1::fffe ipv6.dns 2001:db8:1::ffbb ipv6.dns-search example.com
Re-activate the connection:
# nmcli connection up Office
Verification
Display the active connections:
# nmcli connection show --active NAME ID TYPE DEVICE Office 2501eb7e-7b16-4dc6-97ef-7cc460139a58 wifi wlp0s20f3
If the output lists the wifi connection you have created, the connection is active.
Ping a hostname or IP address:
# ping -c 3 example.com
Additional resources
-
nm-settings-nmcli(5)
man page
10.4. Connecting to a wifi network by using the GNOME settings application
You can use the GNOME settings
application, also named gnome-control-center
, to connect to a wifi network and configure the connection. When you connect to the network for the first time, GNOME creates a NetworkManager connection profile for it.
In GNOME settings
, you can configure wifi connections for all wifi network security types that RHEL supports.
Prerequisites
- A wifi device is installed on the host.
- The wifi device is enabled, if it has a hardware switch.
Procedure
-
Press the Super key, type
Wi-Fi
, and press Enter. - Click on the name of the wifi network you want to connect to.
-
Enter the password for the network, and click
Connect
. If the network requires additional settings, such as static IP addresses or a security type other than WPA2 Personal:
- Click the gear icon next to the network’s name.
Optional: Configure the network profile on the
Details
tab to not automatically connect.If you deactivate this feature, you must always manually connect to the network, for example, by using
GNOME settings
or the GNOME system menu.-
Configure IPv4 settings on the
IPv4
tab, and IPv6 settings on theIPv6
tab. On the
Security
tab, select the authentication of the network, such asWPA3 Personal
, and enter the password.Depending on the selected security, the application shows additional fields. Fill them accordingly. For details, ask the administrator of the wifi network.
-
Click
Apply
.
Verification
Open the system menu on the right side of the top bar, and verify that the wifi network is connected:
If the network appears in the list, it is connected.
Ping a hostname or IP address:
# ping -c 3 example.com
10.5. Configuring a wifi connection by using nmtui
The nmtui
application provides a text-based user interface for NetworkManager. You can use nmtui
to connect to a wifi network.
In nmtui
:
- Navigate by using the cursor keys.
- Press a button by selecting it and hitting Enter.
- Select and clear checkboxes by using Space.
Procedure
If you do not know the network device name you want to use in the connection, display the available devices:
# nmcli device status DEVICE TYPE STATE CONNECTION wlp2s0 wifi unavailable -- ...
Start
nmtui
:# nmtui
-
Select
Edit a connection
, and press Enter. -
Press the
Add
button. -
Select
Wi-Fi
from the list of network types, and press Enter. Optional: Enter a name for the NetworkManager profile to be created.
On hosts with multiple profiles, a meaningful name makes it easier to identify the purpose of a profile.
-
Enter the network device name into the
Device
field. -
Enter the name of the Wi-Fi network, the Service Set Identifier (SSID), into the
SSID
field. -
Leave the
Mode
field set to its default,Client
. Select the
Security
field, press Enter, and set the authentication type of the network from the list.Depending on the authentication type you have selected,
nmtui
displays different fields.- Fill the authentication type-related fields.
If the Wi-Fi network requires static IP addresses:
-
Press the
Automatic
button next to the protocol, and selectManual
from the displayed list. -
Press the
Show
button next to the protocol you want to configure to display additional fields, and fill them.
-
Press the
Press the
OK
button to create and automatically activate the new connection.-
Press the
Back
button to return to the main menu. -
Select
Quit
, and press Enter to close thenmtui
application.
Verification
Display the active connections:
# nmcli connection show --active NAME ID TYPE DEVICE Office 2501eb7e-7b16-4dc6-97ef-7cc460139a58 wifi wlp0s20f3
If the output lists the wifi connection you have created, the connection is active.
Ping a hostname or IP address:
# ping -c 3 example.com
10.6. Configuring a wifi connection by using nm-connection-editor
You can use the nm-connection-editor
application to create a connection profile for a wireless network. In this application you can configure all wifi network authentication types that RHEL supports.
By default, NetworkManager enables the auto-connect feature for connection profiles and automatically connects to a saved network if it is available.
Prerequisites
- A wifi device is installed on the host.
- The wifi device is enabled, if it has a hardware switch.
Procedure
Open a terminal and enter:
# nm-connection-editor
- Click the button to add a new connection.
-
Select the
Wi-Fi
connection type, and click . - Optional: Set a name for the connection profile.
Optional: Configure the network profile on the
General
tab to not automatically connect.If you deactivate this feature, you must always manually connect to the network, for example, by using
GNOME settings
or the GNOME system menu.-
On the
Wi-Fi
tab, enter the service set identifier (SSID) in theSSID
field. On the
Wi-Fi Security
tab, select the authentication type for the network, such asWPA3 Personal
, and enter the password.Depending on the selected security, the application shows additional fields. Fill them accordingly. For details, ask the administrator of the wifi network.
-
Configure IPv4 settings on the
IPv4
tab, and IPv6 settings on theIPv6
tab. -
Click
Save
. -
Close the
Network Connections
window.
Verification
Open the system menu on the right side of the top bar, and verify that the wifi network is connected:
If the network appears in the list, it is connected.
Ping a hostname or IP address:
# ping -c 3 example.com
10.7. Configuring a wifi connection with 802.1X network authentication by using the network
RHEL system role
Network Access Control (NAC) protects a network from unauthorized clients. You can specify the details that are required for the authentication in NetworkManager connection profiles to enable clients to access the network. By using Ansible and the network
RHEL system role, you can automate this process and remotely configure connection profiles on the hosts defined in a playbook.
You can use an Ansible playbook to copy a private key, a certificate, and the CA certificate to the client, and then use the network
RHEL system role to configure a connection profile with 802.1X network authentication.
Prerequisites
- You have prepared the control node and the managed nodes
- You are logged in to the control node as a user who can run playbooks on the managed nodes.
-
The account you use to connect to the managed nodes has
sudo
permissions on them. - The network supports 802.1X network authentication.
-
You installed the
wpa_supplicant
package on the managed node. - DHCP is available in the network of the managed node.
The following files required for TLS authentication exist on the control node:
-
The client key is stored in the
/srv/data/client.key
file. -
The client certificate is stored in the
/srv/data/client.crt
file. -
The CA certificate is stored in the
/srv/data/ca.crt
file.
-
The client key is stored in the
Procedure
Store your sensitive variables in an encrypted file:
Create the vault:
$ ansible-vault create vault.yml New Vault password: <vault_password> Confirm New Vault password: <vault_password>
After the
ansible-vault create
command opens an editor, enter the sensitive data in the<key>: <value>
format:pwd: <password>
- Save the changes, and close the editor. Ansible encrypts the data in the vault.
Create a playbook file, for example
~/playbook.yml
, with the following content:--- - name: Configure a wifi connection with 802.1X authentication hosts: managed-node-01.example.com tasks: - name: Copy client key for 802.1X authentication ansible.builtin.copy: src: "/srv/data/client.key" dest: "/etc/pki/tls/private/client.key" mode: 0400 - name: Copy client certificate for 802.1X authentication ansible.builtin.copy: src: "/srv/data/client.crt" dest: "/etc/pki/tls/certs/client.crt" - name: Copy CA certificate for 802.1X authentication ansible.builtin.copy: src: "/srv/data/ca.crt" dest: "/etc/pki/ca-trust/source/anchors/ca.crt" - name: Wifi connection profile with dynamic IP address settings and 802.1X ansible.builtin.import_role: name: rhel-system-roles.network vars: network_connections: - name: Wifi connection profile with dynamic IP address settings and 802.1X interface_name: wlp1s0 state: up type: wireless autoconnect: yes ip: dhcp4: true auto6: true wireless: ssid: "Example-wifi" key_mgmt: "wpa-eap" ieee802_1x: identity: <user_name> eap: tls private_key: "/etc/pki/tls/client.key" private_key_password: "{{ pwd }}" private_key_password_flags: none client_cert: "/etc/pki/tls/client.pem" ca_cert: "/etc/pki/tls/cacert.pem" domain_suffix_match: "example.com"
The settings specified in the example playbook include the following:
ieee802_1x
- This variable contains the 802.1X-related settings.
eap: tls
-
Configures the profile to use the certificate-based
TLS
authentication method for the Extensible Authentication Protocol (EAP).
For details about all variables used in the playbook, see the
/usr/share/ansible/roles/rhel-system-roles.network/README.md
file on the control node.Validate the playbook syntax:
$ ansible-playbook --ask-vault-pass --syntax-check ~/playbook.yml
Note that this command only validates the syntax and does not protect against a wrong but valid configuration.
Run the playbook:
$ ansible-playbook --ask-vault-pass ~/playbook.yml
Additional resources
-
/usr/share/ansible/roles/rhel-system-roles.network/README.md
file -
/usr/share/doc/rhel-system-roles/network/
directory
10.8. Configuring a wifi connection with 802.1X network authentication in an existing profile by using nmcli
Using the nmcli
utility, you can configure the client to authenticate itself to the network. For example, you can configure Protected Extensible Authentication Protocol (PEAP) authentication with the Microsoft Challenge-Handshake Authentication Protocol version 2 (MSCHAPv2) in an existing NetworkManager wifi connection profile named wlp1s0
.
Prerequisites
- The network must have 802.1X network authentication.
- The wifi connection profile exists in NetworkManager and has a valid IP configuration.
-
If the client is required to verify the certificate of the authenticator, the Certificate Authority (CA) certificate must be stored in the
/etc/pki/ca-trust/source/anchors/
directory. -
The
wpa_supplicant
package is installed.
Procedure
Set the wifi security mode to
wpa-eap
, the Extensible Authentication Protocol (EAP) topeap
, the inner authentication protocol tomschapv2
, and the user name:# nmcli connection modify wlp1s0 wireless-security.key-mgmt wpa-eap 802-1x.eap peap 802-1x.phase2-auth mschapv2 802-1x.identity user_name
Note that you must set the
wireless-security.key-mgmt
,802-1x.eap
,802-1x.phase2-auth
, and802-1x.identity
parameters in a single command.Optional: Store the password in the configuration:
# nmcli connection modify wlp1s0 802-1x.password password
ImportantBy default, NetworkManager stores the password in plain text in the
/etc/sysconfig/network-scripts/keys-connection_name
file, which is readable only by theroot
user. However, plain text passwords in a configuration file can be a security risk.To increase the security, set the
802-1x.password-flags
parameter to0x1
. With this setting, on servers with the GNOME desktop environment or thenm-applet
running, NetworkManager retrieves the password from these services. In other cases, NetworkManager prompts for the password.If the client needs to verify the certificate of the authenticator, set the
802-1x.ca-cert
parameter in the connection profile to the path of the CA certificate:# nmcli connection modify wlp1s0 802-1x.ca-cert /etc/pki/ca-trust/source/anchors/ca.crt
NoteFor security reasons, clients should validate the certiciate of the authenticator.
Activate the connection profile:
# nmcli connection up wlp1s0
Verification
- Access resources on the network that require network authentication.
Additional resources
- Managing wifi connections
-
nm-settings(5)
man page -
nmcli(1)
man page
10.9. Manually setting the wireless regulatory domain
On RHEL, a udev
rule executes the setregdomain
utility to set the wireless regulatory domain. The utility then provides this information to the kernel.
By default, setregdomain
attempts to determine the country code automatically. If this fails, the wireless regulatory domain setting might be wrong. To work around this problem, you can manually set the country code.
Manually setting the regulatory domain disables the automatic detection. Therefore, if you later use the computer in a different country, the previously configured setting might no longer be correct. In this case, remove the /etc/sysconfig/regdomain
file to switch back to automatic detection or use this procedure to manually update the regulatory domain setting again.
Procedure
Optional: Display the current regulatory domain settings:
# iw reg get global country US: DFS-FCC ...
Create the
/etc/sysconfig/regdomain
file with the following content:COUNTRY=<country_code>
Set the
COUNTRY
variable to an ISO 3166-1 alpha2 country code, such asDE
for Germany orUS
for the United States of America.Set the regulatory domain:
# setregdomain
Verification
Display the regulatory domain settings:
# iw reg get global country DE: DFS-ETSI ...
Additional resources
-
setregdomain(1)
man page -
iw(8)
man page -
regulatory.bin(5)
man page - ISO 3166 Country Codes
Chapter 11. Configuring RHEL as a WPA2 or WPA3 Personal access point
On a host with a wifi device, you can use NetworkManager to configure this host as an access point. Wi-Fi Protected Access 2 (WPA2) and Wi-Fi Protected Access 3 (WPA3) Personal provide secure authentication methods, and wireless clients can use a pre-shared key (PSK) to connect to the access point and use services on the RHEL host and in the network.
When you configure an access point, NetworkManager automatically:
-
Configures the
dnsmasq
service to provide DHCP and DNS services for clients - Enables IP forwarding
-
Adds
nftables
firewall rules to masquerade traffic from the wifi device and configures IP forwarding
Prerequisites
- The wifi device supports running in access point mode.
- The wifi device is not in use.
- The host has internet access.
Procedure
List the wifi devices to identify the one that should provide the access point:
# nmcli device status | grep wifi wlp0s20f3 wifi disconnected --
Verify that the device supports the access point mode:
# nmcli -f WIFI-PROPERTIES.AP device show wlp0s20f3 WIFI-PROPERTIES.AP: yes
To use a wifi device as an access point, the device must support this feature.
Install the
dnsmasq
andNetworkManager-wifi
packages:# yum install dnsmasq NetworkManager-wifi
NetworkManager uses the
dnsmasq
service to provide DHCP and DNS services to clients of the access point.Create the initial access point configuration:
# nmcli device wifi hotspot ifname wlp0s20f3 con-name Example-Hotspot ssid Example-Hotspot password "password"
This command creates a connection profile for an access point on the
wlp0s20f3
device that provides WPA2 and WPA3 Personal authentication. The name of the wireless network, the Service Set Identifier (SSID), isExample-Hotspot
and uses the pre-shared keypassword
.Optional: Configure the access point to support only WPA3:
# nmcli connection modify Example-Hotspot 802-11-wireless-security.key-mgmt sae
By default, NetworkManager uses the IP address
10.42.0.1
for the wifi device and assigns IP addresses from the remaining10.42.0.0/24
subnet to clients. To configure a different subnet and IP address, enter:# nmcli connection modify Example-Hotspot ipv4.addresses 192.0.2.254/24
The IP address you set, in this case
192.0.2.254
, is the one that NetworkManager assigns to the wifi device. Clients will use this IP address as default gateway and DNS server.Activate the connection profile:
# nmcli connection up Example-Hotspot
Verification
On the server:
Verify that NetworkManager started the
dnsmasq
service and that the service listens on port 67 (DHCP) and 53 (DNS):# ss -tulpn | egrep ":53|:67" udp UNCONN 0 0 10.42.0.1:53 0.0.0.0:* users:(("dnsmasq",pid=55905,fd=6)) udp UNCONN 0 0 0.0.0.0:67 0.0.0.0:* users:(("dnsmasq",pid=55905,fd=4)) tcp LISTEN 0 32 10.42.0.1:53 0.0.0.0:* users:(("dnsmasq",pid=55905,fd=7))
Display the
nftables
rule set to ensure that NetworkManager enabled forwarding and masquerading for traffic from the10.42.0.0/24
subnet:# nft list ruleset table ip nm-shared-wlp0s20f3 { chain nat_postrouting { type nat hook postrouting priority srcnat; policy accept; ip saddr 10.42.0.0/24 ip daddr != 10.42.0.0/24 masquerade } chain filter_forward { type filter hook forward priority filter; policy accept; ip daddr 10.42.0.0/24 oifname "wlp0s20f3" ct state { established, related } accept ip saddr 10.42.0.0/24 iifname "wlp0s20f3" accept iifname "wlp0s20f3" oifname "wlp0s20f3" accept iifname "wlp0s20f3" reject oifname "wlp0s20f3" reject } }
On a client with a wifi adapter:
Display the list of available networks:
# nmcli device wifi IN-USE BSSID SSID MODE CHAN RATE SIGNAL BARS SECURITY 00:53:00:88:29:04 Example-Hotspot Infra 11 130 Mbit/s 62 ▂▄▆_ WPA3 ...
-
Connect to the
Example-Hotspot
wireless network. See Managing Wi-Fi connections. Ping a host on the remote network or the internet to verify that the connection works:
# ping -c 3 www.redhat.com
Additional resources
-
nm-settings(5)
man page
Chapter 12. Using MACsec to encrypt layer-2 traffic in the same physical network
You can use MACsec to secure the communication between two devices (point-to-point). For example, your branch office is connected over a Metro-Ethernet connection with the central office, you can configure MACsec on the two hosts that connect the offices to increase the security.
Media Access Control security (MACsec) is a layer 2 protocol that secures different traffic types over the Ethernet links including:
- dynamic host configuration protocol (DHCP)
- address resolution protocol (ARP)
-
Internet Protocol version 4 / 6 (
IPv4
/IPv6
) and - any traffic over IP such as TCP or UDP
MACsec encrypts and authenticates all traffic in LANs, by default with the GCM-AES-128 algorithm, and uses a pre-shared key to establish the connection between the participant hosts. If you want to change the pre-shared key, you need to update the NM configuration on all hosts in the network that uses MACsec.
A MACsec connection uses an Ethernet device, such as an Ethernet network card, VLAN, or tunnel device, as parent. You can either set an IP configuration only on the MACsec device to communicate with other hosts only using the encrypted connection, or you can also set an IP configuration on the parent device. In the latter case, you can use the parent device to communicate with other hosts using an unencrypted connection and the MACsec device for encrypted connections.
MACsec does not require any special hardware. For example, you can use any switch, except if you want to encrypt traffic only between a host and a switch. In this scenario, the switch must also support MACsec.
In other words, there are 2 common methods to configure MACsec;
- host to host and
- host to switch then switch to other host(s)
You can use MACsec only between hosts that are in the same (physical or virtual) LAN.
12.1. Configuring a MACsec connection by using nmcli
You can configure Ethernet interfaces to use MACsec using the nmcli
utility. For example, you can create a MACsec connection between two hosts that are connected over Ethernet.
Procedure
On the first host on which you configure MACsec:
Create the connectivity association key (CAK) and connectivity-association key name (CKN) for the pre-shared key:
Create a 16-byte hexadecimal CAK:
# dd if=/dev/urandom count=16 bs=1 2> /dev/null | hexdump -e '1/2 "%04x"' 50b71a8ef0bd5751ea76de6d6c98c03a
Create a 32-byte hexadecimal CKN:
# dd if=/dev/urandom count=32 bs=1 2> /dev/null | hexdump -e '1/2 "%04x"' f2b4297d39da7330910a74abc0449feb45b5c0b9fc23df1430e1898fcf1c4550
- On both hosts you want to connect over a MACsec connection:
Create the MACsec connection:
# nmcli connection add type macsec con-name macsec0 ifname macsec0 connection.autoconnect yes macsec.parent enp1s0 macsec.mode psk macsec.mka-cak 50b71a8ef0bd5751ea76de6d6c98c03a macsec.mka-ckn f2b4297d39da7330910a74abc0449feb45b5c0b9fc23df1430e1898fcf1c4550
Use the CAK and CKN generated in the previous step in the
macsec.mka-cak
andmacsec.mka-ckn
parameters. The values must be the same on every host in the MACsec-protected network.Configure the IP settings on the MACsec connection.
Configure the
IPv4
settings. For example, to set a staticIPv4
address, network mask, default gateway, and DNS server to themacsec0
connection, enter:# nmcli connection modify macsec0 ipv4.method manual ipv4.addresses '192.0.2.1/24' ipv4.gateway '192.0.2.254' ipv4.dns '192.0.2.253'
Configure the
IPv6
settings. For example, to set a staticIPv6
address, network mask, default gateway, and DNS server to themacsec0
connection, enter:# nmcli connection modify macsec0 ipv6.method manual ipv6.addresses '2001:db8:1::1/32' ipv6.gateway '2001:db8:1::fffe' ipv6.dns '2001:db8:1::fffd'
Activate the connection:
# nmcli connection up macsec0
Verification
Verify that the traffic is encrypted:
# tcpdump -nn -i enp1s0
Optional: Display the unencrypted traffic:
# tcpdump -nn -i macsec0
Display MACsec statistics:
# ip macsec show
Display individual counters for each type of protection: integrity-only (encrypt off) and encryption (encrypt on)
# ip -s macsec show
12.2. Additional resources
Chapter 13. Getting started with IPVLAN
IPVLAN is a driver for a virtual network device that can be used in container environment to access the host network. IPVLAN exposes a single MAC address to the external network regardless the number of IPVLAN device created inside the host network. This means that a user can have multiple IPVLAN devices in multiple containers and the corresponding switch reads a single MAC address. IPVLAN driver is useful when the local switch imposes constraints on the total number of MAC addresses that it can manage.
13.1. IPVLAN modes
The following modes are available for IPVLAN:
L2 mode
In IPVLAN L2 mode, virtual devices receive and respond to address resolution protocol (ARP) requests. The
netfilter
framework runs only inside the container that owns the virtual device. Nonetfilter
chains are executed in the default namespace on the containerized traffic. Using L2 mode provides good performance, but less control on the network traffic.L3 mode
In L3 mode, virtual devices process only L3 traffic and above. Virtual devices do not respond to ARP request and users must configure the neighbour entries for the IPVLAN IP addresses on the relevant peers manually. The egress traffic of a relevant container is landed on the
netfilter
POSTROUTING and OUTPUT chains in the default namespace while the ingress traffic is threaded in the same way as L2 mode. Using L3 mode provides good control but decreases the network traffic performance.L3S mode
In L3S mode, virtual devices process the same way as in L3 mode, except that both egress and ingress traffics of a relevant container are landed on
netfilter
chain in the default namespace. L3S mode behaves in a similar way to L3 mode but provides greater control of the network.
The IPVLAN virtual device does not receive broadcast and multicast traffic in case of L3 and L3S modes.
13.2. Comparison of IPVLAN and MACVLAN
The following table shows the major differences between MACVLAN and IPVLAN:
MACVLAN | IPVLAN |
---|---|
Uses MAC address for each MACVLAN device. Note that, if a switch reaches the maximum number of MAC addresses it can store in its MAC table, connectivity can be lost. | Uses single MAC address which does not limit the number of IPVLAN devices. |
Netfilter rules for a global namespace cannot affect traffic to or from a MACVLAN device in a child namespace. | It is possible to control traffic to or from a IPVLAN device in L3 mode and L3S mode. |
Both IPVLAN and MACVLAN do not require any level of encapsulation.
13.3. Creating and configuring the IPVLAN device using iproute2
This procedure shows how to set up the IPVLAN device using iproute2
.
Procedure
To create an IPVLAN device, enter the following command:
# ip link add link real_NIC_device name IPVLAN_device type ipvlan mode l2
Note that network interface controller (NIC) is a hardware component which connects a computer to a network.
Example 13.1. Creating an IPVLAN device
# ip link add link enp0s31f6 name my_ipvlan type ipvlan mode l2 # ip link 47: my_ipvlan@enp0s31f6: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN mode DEFAULT group default qlen 1000 link/ether e8:6a:6e:8a:a2:44 brd ff:ff:ff:ff:ff:ff
To assign an
IPv4
orIPv6
address to the interface, enter the following command:# ip addr add dev IPVLAN_device IP_address/subnet_mask_prefix
In case of configuring an IPVLAN device in L3 mode or L3S mode, make the following setups:
Configure the neighbor setup for the remote peer on the remote host:
# ip neigh add dev peer_device IPVLAN_device_IP_address lladdr MAC_address
where MAC_address is the MAC address of the real NIC on which an IPVLAN device is based on.
Configure an IPVLAN device for L3 mode with the following command:
# ip route add dev <real_NIC_device> <peer_IP_address/32>
For L3S mode:
# ip route add dev real_NIC_device peer_IP_address/32
where IP-address represents the address of the remote peer.
To set an IPVLAN device active, enter the following command:
# ip link set dev IPVLAN_device up
To check if the IPVLAN device is active, execute the following command on the remote host:
# ping IP_address
where the IP_address uses the IP address of the IPVLAN device.
Chapter 14. Configuring NetworkManager to ignore certain devices
By default, NetworkManager manages all devices except the loopback (lo
) device. However, you can configure NetworkManager as unmanaged
to ignore certain devices. With this setting, you can manually manage these devices, for example, using a script.
14.1. Permanently configuring a device as unmanaged in NetworkManager
You can permanently configure devices as unmanaged
based on several criteria, such as the interface name, MAC address, or device type.
To temporarily configure network devices as unmanaged
, see Temporarily configuring a device as unmanaged in NetworkManager.
Procedure
Optional: Display the list of devices to identify the device or MAC address you want to set as
unmanaged
:# ip link show ... 2: enp1s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP mode DEFAULT group default qlen 1000 link/ether 52:54:00:74:79:56 brd ff:ff:ff:ff:ff:ff ...
Create the
/etc/NetworkManager/conf.d/99-unmanaged-devices.conf
file with the following content:To configure a specific interface as unmanaged, add:
[keyfile] unmanaged-devices=interface-name:enp1s0
To configure a device with a specific MAC address as unmanaged, add:
[keyfile] unmanaged-devices=mac:52:54:00:74:79:56
To configure all devices of a specific type as unmanaged, add:
[keyfile] unmanaged-devices=type:ethernet
To set multiple devices as unmanaged, separate the entries in the
unmanaged-devices
parameter with a semicolon, for example:[keyfile] unmanaged-devices=interface-name:enp1s0;interface-name:enp7s0
Reload the
NetworkManager
service:# systemctl reload NetworkManager
Verification
Display the list of devices:
# nmcli device status DEVICE TYPE STATE CONNECTION enp1s0 ethernet unmanaged -- ...
The
unmanaged
state next to theenp1s0
device indicates that NetworkManager does not manage this device.
Troubleshooting
If the device is not shown as
unmanaged
, display the NetworkManager configuration:# NetworkManager --print-config ... [keyfile] unmanaged-devices=interface-name:enp1s0 ...
If the output does not match the settings that you configured, ensure that no configuration file with a higher priority overrides your settings. For details about how NetworkManager merges multiple configuration files, see the
NetworkManager.conf(5)
man page.
14.2. Temporarily configuring a device as unmanaged in NetworkManager
You can temporarily configure devices as unmanaged
.
Use this method, for example, for testing purposes. To permanently configure network devices as unmanaged
, see Permanently configuring a device as unmanaged in NetworkManager.
Procedure
Optional: Display the list of devices to identify the device you want to set as
unmanaged
:# nmcli device status DEVICE TYPE STATE CONNECTION enp1s0 ethernet disconnected -- ...
Set the
enp1s0
device to theunmanaged
state:# nmcli device set enp1s0 managed no
Verification
Display the list of devices:
# nmcli device status DEVICE TYPE STATE CONNECTION enp1s0 ethernet unmanaged -- ...
The
unmanaged
state next to theenp1s0
device indicates that NetworkManager does not manage this device.
Additional resources
-
NetworkManager.conf(5)
man page
Chapter 15. Creating a dummy interface
As a Red Hat Enterprise Linux user, you can create and use dummy network interfaces for debugging and testing purposes. A dummy interface provides a device to route packets without actually transmitting them. It enables you to create additional loopback-like devices managed by NetworkManager and makes an inactive SLIP (Serial Line Internet Protocol) address look like a real address for local programs.
15.1. Creating a dummy interface with both an IPv4 and IPv6 address by using nmcli
You can create a dummy interface with various settings, such as IPv4 and IPv6 addresses. After creating the interface, NetworkManager automatically assigns it to the default public
firewalld
zone.
Procedure
Create a dummy interface named
dummy0
with static IPv4 and IPv6 addresses:# nmcli connection add type dummy ifname dummy0 ipv4.method manual ipv4.addresses 192.0.2.1/24 ipv6.method manual ipv6.addresses 2001:db8:2::1/64
NoteTo configure a dummy interface without IPv4 and IPv6 addresses, set both the
ipv4.method
andipv6.method
parameters todisabled
. Otherwise, IP auto-configuration fails, and NetworkManager deactivates the connection and removes the device.
Verification
List the connection profiles:
# nmcli connection show NAME UUID TYPE DEVICE dummy-dummy0 aaf6eb56-73e5-4746-9037-eed42caa8a65 dummy dummy0
Additional resources
-
nm-settings(5)
man page
Chapter 16. Using NetworkManager to disable IPv6 for a specific connection
On a system that uses NetworkManager to manage network interfaces, you can disable the IPv6 protocol if the network only uses IPv4. If you disable IPv6
, NetworkManager automatically sets the corresponding sysctl
values in the Kernel.
If disabling IPv6 using kernel tunables or kernel boot parameters, additional consideration must be given to system configuration. For more information, see the How do I disable or enable the IPv6 protocol in RHEL? article.
16.1. Disabling IPv6 on a connection using nmcli
You can use the nmcli
utility to disable the IPv6
protocol on the command line.
Prerequisites
- The system uses NetworkManager to manage network interfaces.
Procedure
Optional: Display the list of network connections:
# nmcli connection show NAME UUID TYPE DEVICE Example 7a7e0151-9c18-4e6f-89ee-65bb2d64d365 ethernet enp1s0 ...
Set the
ipv6.method
parameter of the connection todisabled
:# nmcli connection modify Example ipv6.method "disabled"
Restart the network connection:
# nmcli connection up Example
Verification
Display the IP settings of the device:
# ip address show enp1s0 2: enp1s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000 link/ether 52:54:00:6b:74:be brd ff:ff:ff:ff:ff:ff inet 192.0.2.1/24 brd 192.10.2.255 scope global noprefixroute enp1s0 valid_lft forever preferred_lft forever
If no
inet6
entry is displayed,IPv6
is disabled on the device.Verify that the
/proc/sys/net/ipv6/conf/enp1s0/disable_ipv6
file now contains the value1
:# cat /proc/sys/net/ipv6/conf/enp1s0/disable_ipv6 1
The value
1
means thatIPv6
is disabled for the device.
Chapter 17. Changing a hostname
The hostname of a system is the name on the system itself. You can set the name when you install RHEL, and you can change it afterwards.
17.1. Changing a hostname by using nmcli
You can use the nmcli
utility to update the system hostname. Note that other utilities might use a different term, such as static or persistent hostname.
Procedure
Optional: Display the current hostname setting:
# nmcli general hostname old-hostname.example.com
Set the new hostname:
# nmcli general hostname new-hostname.example.com
NetworkManager automatically restarts the
systemd-hostnamed
to activate the new name. For the changes to take effect, reboot the host:# reboot
Alternatively, if you know which services use the hostname:
Restart all services that only read the hostname when the service starts:
# systemctl restart <service_name>
- Active shell users must re-login for the changes to take effect.
Verification
Display the hostname:
# nmcli general hostname new-hostname.example.com
17.2. Changing a hostname by using hostnamectl
You can use the hostnamectl
utility to update the hostname. By default, this utility sets the following hostname types:
-
Static hostname: Stored in the
/etc/hostname
file. Typically, services use this name as the hostname. -
Pretty hostname: A descriptive name, such as
Proxy server in data center A
. - Transient hostname: A fall-back value that is typically received from the network configuration.
Procedure
Optional: Display the current hostname setting:
# hostnamectl status --static old-hostname.example.com
Set the new hostname:
# hostnamectl set-hostname new-hostname.example.com
This command sets the static, pretty, and transient hostname to the new value. To set only a specific type, pass the
--static
,--pretty
, or--transient
option to the command.The
hostnamectl
utility automatically restarts thesystemd-hostnamed
to activate the new name. For the changes to take effect, reboot the host:# reboot
Alternatively, if you know which services use the hostname:
Restart all services that only read the hostname when the service starts:
# systemctl restart <service_name>
- Active shell users must re-login for the changes to take effect.
Verification
Display the hostname:
# hostnamectl status --static new-hostname.example.com
Chapter 18. Configuring NetworkManager DHCP settings
NetworkManager provides different configuration options related to DHCP. For example, you can configure NetworkManager to use the build-in DHCP client (default) or an external client, and you can influence DHCP settings of individual profiles.
18.1. Changing the DHCP client of NetworkManager
By default, NetworkManager uses its internal DHCP client. However, if you require a DHCP client with features that the built-in client does not provide, you can alternatively configure NetworkManager to use dhclient
.
Note that RHEL does not provide dhcpcd
and, therefore, NetworkManager can not use this client.
Procedure
Create the
/etc/NetworkManager/conf.d/dhcp-client.conf
file with the following content:[main] dhcp=dhclient
You can set the
dhcp
parameter tointernal
(default) ordhclient
.If you set the
dhcp
parameter todhclient
, install thedhcp-client
package:# yum install dhcp-client
Restart NetworkManager:
# systemctl restart NetworkManager
Note that the restart temporarily interrupts all network connections.
Verification
Search in the
/var/log/messages
log file for an entry similar to the following:Apr 26 09:54:19 server NetworkManager[27748]: <info> [1650959659.8483] dhcp-init: Using DHCP client 'dhclient'
This log entry confirms that NetworkManager uses
dhclient
as DHCP client.
Additional resources
-
NetworkManager.conf(5)
man page
18.2. Configuring the DHCP behavior of a NetworkManager connection
A Dynamic Host Configuration Protocol (DHCP) client requests the dynamic IP address and corresponding configuration information from a DHCP server each time a client connects to the network.
When you configured a connection to retrieve an IP address from a DHCP server, the NetworkManager requests an IP address from a DHCP server. By default, the client waits 45 seconds for this request to be completed. When a DHCP
connection is started, a dhcp client requests an IP address from a DHCP
server.
Prerequisites
- A connection that uses DHCP is configured on the host.
Procedure
Set the
ipv4.dhcp-timeout
andipv6.dhcp-timeout
properties. For example, to set both options to30
seconds, enter:# nmcli connection modify <connection_name> ipv4.dhcp-timeout 30 ipv6.dhcp-timeout 30
Alternatively, set the parameters to
infinity
to configure that NetworkManager does not stop trying to request and renew an IP address until it is successful.Optional: Configure the behavior if NetworkManager does not receive an IPv4 address before the timeout:
# nmcli connection modify <connection_name> ipv4.may-fail <value>
If you set the
ipv4.may-fail
option to:yes
, the status of the connection depends on the IPv6 configuration:- If the IPv6 configuration is enabled and successful, NetworkManager activates the IPv6 connection and no longer tries to activate the IPv4 connection.
- If the IPv6 configuration is disabled or not configured, the connection fails.
no
, the connection is deactivated. In this case:-
If the
autoconnect
property of the connection is enabled, NetworkManager retries to activate the connection as many times as set in theautoconnect-retries
property. The default is4
. - If the connection still cannot acquire a DHCP address, auto-activation fails. Note that after 5 minutes, the auto-connection process starts again to acquire an IP address from the DHCP server.
-
If the
Optional: Configure the behavior if NetworkManager does not receive an IPv6 address before the timeout:
# nmcli connection modify <connection_name> ipv6.may-fail <value>
Additional resources
-
nm-settings(5)
man page
Chapter 19. Running dhclient exit hooks using NetworkManager a dispatcher script
You can use a NetworkManager dispatcher script to execute dhclient
exit hooks.
19.1. The concept of NetworkManager dispatcher scripts
The NetworkManager-dispatcher
service executes user-provided scripts in alphabetical order when network events happen. These scripts are typically shell scripts, but can be any executable script or application. You can use dispatcher scripts, for example, to adjust network-related settings that you cannot manage with NetworkManager.
You can store dispatcher scripts in the following directories:
-
/etc/NetworkManager/dispatcher.d/
: The general location for dispatcher scripts theroot
user can edit. -
/usr/lib/NetworkManager/dispatcher.d/
: For pre-deployed immutable dispatcher scripts.
For security reasons, the NetworkManager-dispatcher
service executes scripts only if the following conditions met:
-
The script is owned by the
root
user. -
The script is only readable and writable by
root
. -
The
setuid
bit is not set on the script.
The NetworkManager-dispatcher
service runs each script with two arguments:
- The interface name of the device the operation happened on.
-
The action, such as
up
, when the interface has been activated.
The Dispatcher scripts
section in the NetworkManager(8)
man page provides an overview of actions and environment variables you can use in scripts.
The NetworkManager-dispatcher
service runs one script at a time, but asynchronously from the main NetworkManager process. Note that, if a script is queued, the service will always run it, even if a later event makes it obsolete. However, the NetworkManager-dispatcher
service runs scripts that are symbolic links referring to files in /etc/NetworkManager/dispatcher.d/no-wait.d/
immediately, without waiting for the termination of previous scripts, and in parallel.
Additional resources
-
NetworkManager(8)
man page
19.2. Creating a NetworkManager dispatcher script that runs dhclient exit hooks
When a DHCP server assigns or updates an IPv4 address, NetworkManager can run a dispatcher script stored in the /etc/dhcp/dhclient-exit-hooks.d/
directory. This dispatcher script can then, for example, run dhclient
exit hooks.
Prerequisites
-
The
dhclient
exit hooks are stored in the/etc/dhcp/dhclient-exit-hooks.d/
directory.
Procedure
Create the
/etc/NetworkManager/dispatcher.d/12-dhclient-down
file with the following content:#!/bin/bash # Run dhclient.exit-hooks.d scripts if [ -n "$DHCP4_DHCP_LEASE_TIME" ] ; then if [ "$2" = "dhcp4-change" ] || [ "$2" = "up" ] ; then if [ -d /etc/dhcp/dhclient-exit-hooks.d ] ; then for f in /etc/dhcp/dhclient-exit-hooks.d/*.sh ; do if [ -x "${f}" ]; then . "${f}" fi done fi fi fi
Set the
root
user as owner of the file:# chown root:root /etc/NetworkManager/dispatcher.d/12-dhclient-down
Set the permissions so that only the root user can execute it:
# chmod 0700 /etc/NetworkManager/dispatcher.d/12-dhclient-down
Restore the SELinux context:
# restorecon /etc/NetworkManager/dispatcher.d/12-dhclient-down
Additional resources
-
NetworkManager(8)
man page
Chapter 20. Manually configuring the /etc/resolv.conf file
By default, NetworkManager dynamically updates the /etc/resolv.conf
file with the DNS settings from active NetworkManager connection profiles. However, you can disable this behavior and manually configure DNS settings in /etc/resolv.conf
.
Alternatively, if you require a specific order of DNS servers in /etc/resolv.conf
, see Configuring the order of DNS servers.
20.1. Disabling DNS processing in the NetworkManager configuration
By default, NetworkManager manages DNS settings in the /etc/resolv.conf
file, and you can configure the order of DNS servers. Alternatively, you can disable DNS processing in NetworkManager if you prefer to manually configure DNS settings in /etc/resolv.conf
.
Procedure
As the root user, create the
/etc/NetworkManager/conf.d/90-dns-none.conf
file with the following content by using a text editor:[main] dns=none
Reload the
NetworkManager
service:# systemctl reload NetworkManager
NoteAfter you reload the service, NetworkManager no longer updates the
/etc/resolv.conf
file. However, the last contents of the file are preserved.-
Optional: Remove the
Generated by NetworkManager
comment from/etc/resolv.conf
to avoid confusion.
Verification
-
Edit the
/etc/resolv.conf
file and manually update the configuration. Reload the
NetworkManager
service:# systemctl reload NetworkManager
Display the
/etc/resolv.conf
file:# cat /etc/resolv.conf
If you successfully disabled DNS processing, NetworkManager did not override the manually configured settings.
Troubleshooting
Display the NetworkManager configuration to ensure that no other configuration file with a higher priority overrode the setting:
# NetworkManager --print-config ... dns=none ...
Additional resources
-
NetworkManager.conf(5)
man page - Configuring the order of DNS servers using NetworkManager
20.2. Replacing /etc/resolv.conf with a symbolic link to manually configure DNS settings
By default, NetworkManager manages DNS settings in the /etc/resolv.conf
file, and you can configure the order of DNS servers. Alternatively, you can disable DNS processing in NetworkManager if you prefer to manually configure DNS settings in /etc/resolv.conf
. For example, NetworkManager does not automatically update the DNS configuration if /etc/resolv.conf
is a symbolic link.
Prerequisites
-
The NetworkManager
rc-manager
configuration option is not set tofile
. To verify, use theNetworkManager --print-config
command.
Procedure
-
Create a file, such as
/etc/resolv.conf.manually-configured
, and add the DNS configuration for your environment to it. Use the same parameters and syntax as in the original/etc/resolv.conf
. Remove the
/etc/resolv.conf
file:# rm /etc/resolv.conf
Create a symbolic link named
/etc/resolv.conf
that refers to/etc/resolv.conf.manually-configured
:# ln -s /etc/resolv.conf.manually-configured /etc/resolv.conf
Additional resources
-
resolv.conf(5)
man page -
NetworkManager.conf(5)
man page - Configuring the order of DNS servers using NetworkManager
Chapter 21. Configuring the order of DNS servers
Most applications use the getaddrinfo()
function of the glibc
library to resolve DNS requests. By default, glibc
sends all DNS requests to the first DNS server specified in the /etc/resolv.conf
file. If this server does not reply, RHEL uses the next server in this file. NetworkManager enables you to influence the order of DNS servers in etc/resolv.conf
.
21.1. How NetworkManager orders DNS servers in /etc/resolv.conf
NetworkManager orders DNS servers in the /etc/resolv.conf
file based on the following rules:
- If only one connection profile exists, NetworkManager uses the order of IPv4 and IPv6 DNS server specified in that connection.
If multiple connection profiles are activated, NetworkManager orders DNS servers based on a DNS priority value. If you set DNS priorities, the behavior of NetworkManager depends on the value set in the
dns
parameter. You can set this parameter in the[main]
section in the/etc/NetworkManager/NetworkManager.conf
file:dns=default
or if thedns
parameter is not set:NetworkManager orders the DNS servers from different connections based on the
ipv4.dns-priority
andipv6.dns-priority
parameter in each connection.If you set no value or you set
ipv4.dns-priority
andipv6.dns-priority
to0
, NetworkManager uses the global default value. See Default values of DNS priority parameters.dns=dnsmasq
ordns=systemd-resolved
:When you use one of these settings, NetworkManager sets either
127.0.0.1
fordnsmasq
or127.0.0.53
asnameserver
entry in the/etc/resolv.conf
file.Both the
dnsmasq
andsystemd-resolved
services forward queries for the search domain set in a NetworkManager connection to the DNS server specified in that connection, and forwardes queries to other domains to the connection with the default route. When multiple connections have the same search domain set,dnsmasq
andsystemd-resolved
forward queries for this domain to the DNS server set in the connection with the lowest priority value.
Default values of DNS priority parameters
NetworkManager uses the following default values for connections:
-
50
for VPN connections -
100
for other connections
Valid DNS priority values:
You can set both the global default and connection-specific ipv4.dns-priority
and ipv6.dns-priority
parameters to a value between -2147483647
and 2147483647
.
- A lower value has a higher priority.
- Negative values have the special effect of excluding other configurations with a greater value. For example, if at least one connection with a negative priority value exists, NetworkManager uses only the DNS servers specified in the connection profile with the lowest priority.
If multiple connections have the same DNS priority, NetworkManager prioritizes the DNS in the following order:
- VPN connections
- Connection with an active default route. The active default route is the default route with the lowest metric.
Additional resources
-
nm-settings(5)
man page - Using different DNS servers for different domains
21.2. Setting a NetworkManager-wide default DNS server priority value
NetworkManager uses the following DNS priority default values for connections:
-
50
for VPN connections -
100
for other connections
You can override these system-wide defaults with a custom default value for IPv4 and IPv6 connections.
Procedure
Edit the
/etc/NetworkManager/NetworkManager.conf
file:Add the
[connection]
section, if it does not exist:[connection]
Add the custom default values to the
[connection]
section. For example, to set the new default for both IPv4 and IPv6 to200
, add:ipv4.dns-priority=200 ipv6.dns-priority=200
You can set the parameters to a value between
-2147483647
and2147483647
. Note that setting the parameters to0
enables the built-in defaults (50
for VPN connections and100
for other connections).
Reload the
NetworkManager
service:# systemctl reload NetworkManager
Additional resources
-
NetworkManager.conf(5)
man page
21.3. Setting the DNS priority of a NetworkManager connection
If you require a specific order of DNS servers you can set priority values in connection profiles. NetworkManager uses these values to order the servers when the service creates or updates the /etc/resolv.conf
file.
Note that setting DNS priorities makes only sense if you have multiple connections with different DNS servers configured. If you have only one connection with multiple DNS servers configured, manually set the DNS servers in the preferred order in the connection profile.
Prerequisites
- The system has multiple NetworkManager connections configured.
-
The system either has no
dns
parameter set in the/etc/NetworkManager/NetworkManager.conf
file or the parameter is set todefault
.
Procedure
Optional: Display the available connections:
# nmcli connection show NAME UUID TYPE DEVICE Example_con_1 d17ee488-4665-4de2-b28a-48befab0cd43 ethernet enp1s0 Example_con_2 916e4f67-7145-3ffa-9f7b-e7cada8f6bf7 ethernet enp7s0 ...
Set the
ipv4.dns-priority
andipv6.dns-priority
parameters. For example, to set both parameters to10
, enter:# nmcli connection modify <connection_name> ipv4.dns-priority 10 ipv6.dns-priority 10
- Optional: Repeat the previous step for other connections.
Re-activate the connection you updated:
# nmcli connection up <connection_name>
Verification
Display the contents of the
/etc/resolv.conf
file to verify that the DNS server order is correct:# cat /etc/resolv.conf
Chapter 22. Using different DNS servers for different domains
By default, Red Hat Enterprise Linux (RHEL) sends all DNS requests to the first DNS server specified in the /etc/resolv.conf
file. If this server does not reply, RHEL uses the next server in this file. In environments where one DNS server cannot resolve all domains, administrators can configure RHEL to send DNS requests for a specific domain to a selected DNS server.
For example, you connect a server to a Virtual Private Network (VPN), and hosts in the VPN use the example.com
domain. In this case, you can configure RHEL to process DNS queries in the following way:
-
Send only DNS requests for
example.com
to the DNS server in the VPN network. - Send all other requests to the DNS server that is configured in the connection profile with the default gateway.
22.1. Using dnsmasq in NetworkManager to send DNS requests for a specific domain to a selected DNS server
You can configure NetworkManager to start an instance of dnsmasq
. This DNS caching server then listens on port 53
on the loopback
device. Consequently, this service is only reachable from the local system and not from the network.
With this configuration, NetworkManager adds the nameserver 127.0.0.1
entry to the /etc/resolv.conf
file, and dnsmasq
dynamically routes DNS requests to the corresponding DNS servers specified in the NetworkManager connection profiles.
Prerequisites
- The system has multiple NetworkManager connections configured.
A DNS server and search domain are configured in the NetworkManager connection profile that is responsible for resolving a specific domain.
For example, to ensure that the DNS server specified in a VPN connection resolves queries for the
example.com
domain, the VPN connection profile must contain the following settings:-
A DNS server that can resolve
example.com
-
A search domain set to
example.com
in theipv4.dns-search
andipv6.dns-search
parameters
-
A DNS server that can resolve
-
The
dnsmasq
service is not running or configured to listen on a different interface thenlocalhost
.
Procedure
Install the
dnsmasq
package:# yum install dnsmasq
Edit the
/etc/NetworkManager/NetworkManager.conf
file, and set the following entry in the[main]
section:dns=dnsmasq
Reload the
NetworkManager
service:# systemctl reload NetworkManager
Verification
Search in the
systemd
journal of theNetworkManager
unit for which domains the service uses a different DNS server:# journalctl -xeu NetworkManager ... Jun 02 13:30:17 <client_hostname>_ dnsmasq[5298]: using nameserver 198.51.100.7#53 for domain example.com ...
Use the
tcpdump
packet sniffer to verify the correct route of DNS requests:Install the
tcpdump
package:# yum install tcpdump
On one terminal, start
tcpdump
to capture DNS traffic on all interfaces:# tcpdump -i any port 53
On a different terminal, resolve host names for a domain for which an exception exists and another domain, for example:
# host -t A www.example.com # host -t A www.redhat.com
Verify in the
tcpdump
output that Red Hat Enterprise Linux sends only DNS queries for theexample.com
domain to the designated DNS server and through the corresponding interface:... 13:52:42.234533 IP server.43534 > 198.51.100.7.domain: 50121+ [1au] A? www.example.com. (33) ... 13:52:57.753235 IP server.40864 > 192.0.2.1.domain: 6906+ A? www.redhat.com. (33) ...
Red Hat Enterprise Linux sends the DNS query for
www.example.com
to the DNS server on198.51.100.7
and the query forwww.redhat.com
to192.0.2.1
.
Troubleshooting
Verify that the
nameserver
entry in the/etc/resolv.conf
file refers to127.0.0.1
:# cat /etc/resolv.conf nameserver 127.0.0.1
If the entry is missing, check the
dns
parameter in the/etc/NetworkManager/NetworkManager.conf
file.Verify that the
dnsmasq
service listens on port53
on theloopback
device:# ss -tulpn | grep "127.0.0.1:53" udp UNCONN 0 0 127.0.0.1:53 0.0.0.0:* users:(("dnsmasq",pid=7340,fd=18)) tcp LISTEN 0 32 127.0.0.1:53 0.0.0.0:* users:(("dnsmasq",pid=7340,fd=19))
If the service does not listen on
127.0.0.1:53
, check the journal entries of theNetworkManager
unit:# journalctl -u NetworkManager
22.2. Using systemd-resolved in NetworkManager to send DNS requests for a specific domain to a selected DNS server
You can configure NetworkManager to start an instance of systemd-resolved
. This DNS stub resolver then listens on port 53
on IP address 127.0.0.53
. Consequently, this stub resolver is only reachable from the local system and not from the network.
With this configuration, NetworkManager adds the nameserver 127.0.0.53
entry to the /etc/resolv.conf
file, and systemd-resolved
dynamically routes DNS requests to the corresponding DNS servers specified in the NetworkManager connection profiles.
The systemd-resolved
service is provided as a Technology Preview only. Technology Preview features are not supported with Red Hat production Service Level Agreements (SLAs), might not be functionally complete, and Red Hat does not recommend using them for production. These previews provide early access to upcoming product features, enabling customers to test functionality and provide feedback during the development process.
See Technology Preview Features Support Scope on the Red Hat Customer Portal for information about the support scope for Technology Preview features.
For a supported solution, see Using dnsmasq in NetworkManager to send DNS requests for a specific domain to a selected DNS server.
Prerequisites
- The system has multiple NetworkManager connections configured.
A DNS server and search domain are configured in the NetworkManager connection profile that is responsible for resolving a specific domain.
For example, to ensure that the DNS server specified in a VPN connection resolves queries for the
example.com
domain, the VPN connection profile must contain the following settings:-
A DNS server that can resolve
example.com
-
A search domain set to
example.com
in theipv4.dns-search
andipv6.dns-search
parameters
-
A DNS server that can resolve
Procedure
Enable and start the
systemd-resolved
service:# systemctl --now enable systemd-resolved
Edit the
/etc/NetworkManager/NetworkManager.conf
file, and set the following entry in the[main]
section:dns=systemd-resolved
Reload the
NetworkManager
service:# systemctl reload NetworkManager
Verification
Display the DNS servers
systemd-resolved
uses and for which domains the service uses a different DNS server:# resolvectl ... Link 2 (enp1s0) Current Scopes: DNS Protocols: +DefaultRoute ... Current DNS Server: 192.0.2.1 DNS Servers: 192.0.2.1 Link 3 (tun0) Current Scopes: DNS Protocols: -DefaultRoute ... Current DNS Server: 198.51.100.7 DNS Servers: 198.51.100.7 203.0.113.19 DNS Domain: example.com
The output confirms that
systemd-resolved
uses different DNS servers for theexample.com
domain.Use the
tcpdump
packet sniffer to verify the correct route of DNS requests:Install the
tcpdump
package:# yum install tcpdump
On one terminal, start
tcpdump
to capture DNS traffic on all interfaces:# tcpdump -i any port 53
On a different terminal, resolve host names for a domain for which an exception exists and another domain, for example:
# host -t A www.example.com # host -t A www.redhat.com
Verify in the
tcpdump
output that Red Hat Enterprise Linux sends only DNS queries for theexample.com
domain to the designated DNS server and through the corresponding interface:... 13:52:42.234533 IP server.43534 > 198.51.100.7.domain: 50121+ [1au] A? www.example.com. (33) ... 13:52:57.753235 IP server.40864 > 192.0.2.1.domain: 6906+ A? www.redhat.com. (33) ...
Red Hat Enterprise Linux sends the DNS query for
www.example.com
to the DNS server on198.51.100.7
and the query forwww.redhat.com
to192.0.2.1
.
Troubleshooting
Verify that the
nameserver
entry in the/etc/resolv.conf
file refers to127.0.0.53
:# cat /etc/resolv.conf nameserver 127.0.0.53
If the entry is missing, check the
dns
parameter in the/etc/NetworkManager/NetworkManager.conf
file.Verify that the
systemd-resolved
service listens on port53
on the local IP address127.0.0.53
:# ss -tulpn | grep "127.0.0.53" udp UNCONN 0 0 127.0.0.53%lo:53 0.0.0.0:* users:(("systemd-resolve",pid=1050,fd=12)) tcp LISTEN 0 4096 127.0.0.53%lo:53 0.0.0.0:* users:(("systemd-resolve",pid=1050,fd=13))
If the service does not listen on
127.0.0.53:53
, check if thesystemd-resolved
service is running.
Chapter 23. Managing the default gateway setting
The default gateway is a router that forwards network packets when no other route matches the destination of a packet. In a local network, the default gateway is typically the host that is one hop closer to the internet.
23.1. Setting the default gateway on an existing connection by using nmcli
In most situations, administrators set the default gateway when they create a connection. However, you can also set or update the default gateway setting on a previously created connection by using the nmcli
utility.
Prerequisites
- At least one static IP address must be configured on the connection on which the default gateway will be set.
-
If the user is logged in on a physical console, user permissions are sufficient. Otherwise, user must have
root
permissions.
Procedure
Set the IP addresses of the default gateway:
To set the IPv4 default gateway, enter:
# nmcli connection modify <connection_name> ipv4.gateway "<IPv4_gateway_address>"
To set the IPv6 default gateway, enter:
# nmcli connection modify <connection_name> ipv6.gateway "<IPv6_gateway_address>"
Restart the network connection for changes to take effect:
# nmcli connection up <connection_name>
WarningAll connections currently using this network connection are temporarily interrupted during the restart.
Verification
Verify that the route is active:
To display the IPv4 default gateway, enter:
# ip -4 route default via 192.0.2.1 dev example proto static metric 100
To display the IPv6 default gateway, enter:
# ip -6 route default via 2001:db8:1::1 dev example proto static metric 100 pref medium
23.2. Setting the default gateway on an existing connection by using the nmcli
interactive mode
In most situations, administrators set the default gateway when they create a connection. However, you can also set or update the default gateway setting on a previously created connection by using the interactive mode of the nmcli
utility.
Prerequisites
- At least one static IP address must be configured on the connection on which the default gateway will be set.
-
If the user is logged in on a physical console, user permissions are sufficient. Otherwise, the user must have
root
permissions.
Procedure
Open the
nmcli
interactive mode for the required connection:# nmcli connection edit <connection_name>
Set the default gateway
To set the IPv4 default gateway, enter:
nmcli> set ipv4.gateway "<IPv4_gateway_address>"
To set the IPv6 default gateway, enter:
nmcli> set ipv6.gateway "<IPv6_gateway_address>"
Optional: Verify that the default gateway was set correctly:
nmcli> print ... ipv4.gateway: <IPv4_gateway_address> ... ipv6.gateway: <IPv6_gateway_address> ...
Save the configuration:
nmcli> save persistent
Restart the network connection for changes to take effect:
nmcli> activate <connection_name>
WarningAll connections currently using this network connection are temporarily interrupted during the restart.
Leave the
nmcli
interactive mode:nmcli> quit
Verification
Verify that the route is active:
To display the IPv4 default gateway, enter:
# ip -4 route default via 192.0.2.1 dev example proto static metric 100
To display the IPv6 default gateway, enter:
# ip -6 route default via 2001:db8:1::1 dev example proto static metric 100 pref medium
23.3. Setting the default gateway on an existing connection by using nm-connection-editor
In most situations, administrators set the default gateway when they create a connection. However, you can also set or update the default gateway setting on a previously created connection using the nm-connection-editor
application.
Prerequisites
- At least one static IP address must be configured on the connection on which the default gateway will be set.
Procedure
Open a terminal, and enter
nm-connection-editor
:# nm-connection-editor
- Select the connection to modify, and click the gear wheel icon to edit the existing connection.
Set the IPv4 default gateway. For example, to set the IPv4 address of the default gateway on the connection to
192.0.2.1
:-
Open the
IPv4 Settings
tab. Enter the address in the
gateway
field next to the IP range the gateway’s address is within:
-
Open the
Set the IPv6 default gateway. For example, to set the IPv6 address of the default gateway on the connection to
2001:db8:1::1
:-
Open the
IPv6
tab. Enter the address in the
gateway
field next to the IP range the gateway’s address is within:
-
Open the
- Click .
- Click .
Restart the network connection for changes to take effect. For example, to restart the
example
connection using the command line:# nmcli connection up example
WarningAll connections currently using this network connection are temporarily interrupted during the restart.
Verification
Verify that the route is active.
To display the IPv4 default gateway:
# ip -4 route default via 192.0.2.1 dev example proto static metric 100
To display the IPv6 default gateway:
# ip -6 route default via 2001:db8:1::1 dev example proto static metric 100 pref medium
Additional resources
23.4. Setting the default gateway on an existing connection by using control-center
In most situations, administrators set the default gateway when they create a connection. However, you can also set or update the default gateway setting on a previously created connection using the control-center
application.
Prerequisites
- At least one static IP address must be configured on the connection on which the default gateway will be set.
-
The network configuration of the connection is open in the
control-center
application.
Procedure
Set the IPv4 default gateway. For example, to set the IPv4 address of the default gateway on the connection to
192.0.2.1
:-
Open the
IPv4
tab. Enter the address in the
gateway
field next to the IP range the gateway’s address is within:
-
Open the
Set the IPv6 default gateway. For example, to set the IPv6 address of the default gateway on the connection to
2001:db8:1::1
:-
Open the
IPv6
tab. Enter the address in the
gateway
field next to the IP range the gateway’s address is within:
-
Open the
- Click .
Back in the
Network
window, disable and re-enable the connection by switching the button for the connection to and back to for changes to take effect.WarningAll connections currently using this network connection are temporarily interrupted during the restart.
Verification
Verify that the route is active.
To display the IPv4 default gateway:
$ ip -4 route default via 192.0.2.1 dev example proto static metric 100
To display the IPv6 default gateway:
$ ip -6 route default via 2001:db8:1::1 dev example proto static metric 100 pref medium
Additional resources
23.5. Setting the default gateway on an existing connection by using nmstatectl
In most situations, administrators set the default gateway when they create a connection. However, you can also set or update the default gateway setting on a previously created connection by using the nmstatectl
utility.
Use the nmstatectl
utility to set the default gateway through the Nmstate API. The Nmstate API ensures that, after setting the configuration, the result matches the configuration file. If anything fails, nmstatectl
automatically rolls back the changes to avoid leaving the system in an incorrect state.
Prerequisites
- At least one static IP address must be configured on the connection on which the default gateway will be set.
-
The
enp1s0
interface is configured, and the IP address of the default gateway is within the subnet of the IP configuration of this interface. -
The
nmstate
package is installed.
Procedure
Create a YAML file, for example
~/set-default-gateway.yml
, with the following content:--- routes: config: - destination: 0.0.0.0/0 next-hop-address: 192.0.2.1 next-hop-interface: enp1s0
These settings define
192.0.2.1
as the default gateway, and the default gateway is reachable through theenp1s0
interface.Apply the settings to the system:
# nmstatectl apply ~/set-default-gateway.yml
Additional resources
-
nmstatectl(8)
man page -
/usr/share/doc/nmstate/examples/
directory
23.6. Setting the default gateway on an existing connection by using the network
RHEL system role
A host forwards a network packet to its default gateway if the packet’s destination can neither be reached through the directly-connected networks nor through any of the routes configured on the host. To configure the default gateway of a host, set it in the NetworkManager connection profile of the interface that is connected to the same network as the default gateway. By using Ansible and the network
RHEL system role, you can automate this process and remotely configure connection profiles on the hosts defined in a playbook.
In most situations, administrators set the default gateway when they create a connection. However, you can also set or update the default gateway setting on a previously-created connection.
You cannot use the network
RHEL system role to update only specific values in an existing connection profile. The role ensures that a connection profile exactly matches the settings in a playbook. If a connection profile with the same name already exists, the role applies the settings from the playbook and resets all other settings in the profile to their defaults. To prevent resetting values, always specify the whole configuration of the network connection profile in the playbook, including the settings that you do not want to change.
Prerequisites
- You have prepared the control node and the managed nodes
- You are logged in to the control node as a user who can run playbooks on the managed nodes.
-
The account you use to connect to the managed nodes has
sudo
permissions on them.
Procedure
Create a playbook file, for example
~/playbook.yml
, with the following content:--- - name: Configure the network hosts: managed-node-01.example.com tasks: - name: Ethernet connection profile with static IP address settings ansible.builtin.include_role: name: rhel-system-roles.network vars: network_connections: - name: enp1s0 type: ethernet autoconnect: yes ip: address: - 198.51.100.20/24 - 2001:db8:1::1/64 gateway4: 198.51.100.254 gateway6: 2001:db8:1::fffe dns: - 198.51.100.200 - 2001:db8:1::ffbb dns_search: - example.com state: up
For details about all variables used in the playbook, see the
/usr/share/ansible/roles/rhel-system-roles.network/README.md
file on the control node.Validate the playbook syntax:
$ ansible-playbook --syntax-check ~/playbook.yml
Note that this command only validates the syntax and does not protect against a wrong but valid configuration.
Run the playbook:
$ ansible-playbook ~/playbook.yml
Verification
Query the Ansible facts of the managed node and verify the active network settings:
# ansible managed-node-01.example.com -m ansible.builtin.setup ... "ansible_default_ipv4": { ... "gateway": "198.51.100.254", "interface": "enp1s0", ... }, "ansible_default_ipv6": { ... "gateway": "2001:db8:1::fffe", "interface": "enp1s0", ... } ...
Additional resources
-
/usr/share/ansible/roles/rhel-system-roles.network/README.md
file -
/usr/share/doc/rhel-system-roles/network/
directory
23.7. Setting the default gateway on an existing connection when using the legacy network scripts
In most situations, administrators set the default gateway when they create a connection. However, you can also set or update the default gateway setting on a previously created connection when you use the legacy network scripts.
Prerequisites
-
The
NetworkManager
package is not installed, or theNetworkManager
service is disabled. -
The
network-scripts
package is installed.
Procedure
Set the
GATEWAY
parameter in the/etc/sysconfig/network-scripts/ifcfg-enp1s0
file to192.0.2.1
:GATEWAY=192.0.2.1
Add the
default
entry in the/etc/sysconfig/network-scripts/route-enp0s1
file:default via 192.0.2.1
Restart the network:
# systemctl restart network
23.8. How NetworkManager manages multiple default gateways
In certain situations, for example for fallback reasons, you set multiple default gateways on a host. However, to avoid asynchronous routing issues, each default gateway of the same protocol requires a separate metric value. Note that RHEL only uses the connection to the default gateway that has the lowest metric set.
You can set the metric for both the IPv4 and IPv6 gateway of a connection using the following command:
# nmcli connection modify <connection_name> ipv4.route-metric <value> ipv6.route-metric <value>
Do not set the same metric value for the same protocol in multiple connection profiles to avoid routing issues.
If you set a default gateway without a metric value, NetworkManager automatically sets the metric value based on the interface type. For that, NetworkManager assigns the default value of this network type to the first connection that is activated, and sets an incremented value to each other connection of the same type in the order they are activated. For example, if two Ethernet connections with a default gateway exist, NetworkManager sets a metric of 100
on the route to the default gateway of the connection that you activate first. For the second connection, NetworkManager sets 101
.
The following is an overview of frequently-used network types and their default metrics:
Connection type | Default metric value |
---|---|
VPN | 50 |
Ethernet | 100 |
MACsec | 125 |
InfiniBand | 150 |
Bond | 300 |
Team | 350 |
VLAN | 400 |
Bridge | 425 |
TUN | 450 |
Wi-Fi | 600 |
IP tunnel | 675 |
Additional resources
23.9. Configuring NetworkManager to avoid using a specific profile to provide a default gateway
You can configure that NetworkManager never uses a specific profile to provide the default gateway. Follow this procedure for connection profiles that are not connected to the default gateway.
Prerequisites
- The NetworkManager connection profile for the connection that is not connected to the default gateway exists.
Procedure
If the connection uses a dynamic IP configuration, configure that NetworkManager does not use the connection as the default route for IPv4 and IPv6 connections:
# nmcli connection modify <connection_name> ipv4.never-default yes ipv6.never-default yes
Note that setting
ipv4.never-default
andipv6.never-default
toyes
, automatically removes the default gateway’s IP address for the corresponding protocol from the connection profile.Activate the connection:
# nmcli connection up <connection_name>
Verification
-
Use the
ip -4 route
andip -6 route
commands to verify that RHEL does not use the network interface for the default route for the IPv4 and IPv6 protocol.
23.10. Fixing unexpected routing behavior due to multiple default gateways
There are only a few scenarios, such as when using Multipath TCP, in which you require multiple default gateways on a host. In most cases, you configure only a single default gateway to avoid unexpected routing behavior or asynchronous routing issues.
To route traffic to different internet providers, use policy-based routing instead of multiple default gateways.
Prerequisites
- The host uses NetworkManager to manage network connections, which is the default.
- The host has multiple network interfaces.
- The host has multiple default gateways configured.
Procedure
Display the routing table:
For IPv4, enter:
# ip -4 route default via 192.0.2.1 dev enp1s0 proto static metric 101 default via 198.51.100.1 dev enp7s0 proto static metric 102 ...
For IPv6, enter:
# ip -6 route default via 2001:db8:1::1 dev enp1s0 proto static metric 101 pref medium default via 2001:db8:2::1 dev enp7s0 proto static metric 102 pref medium ...
Entries starting with
default
indicate a default route. Note the interface names of these entries displayed next todev
.Use the following commands to display the NetworkManager connections that use the interfaces you identified in the previous step:
# nmcli -f GENERAL.CONNECTION,IP4.GATEWAY,IP6.GATEWAY device show enp1s0 GENERAL.CONNECTION: Corporate-LAN IP4.GATEWAY: 192.0.2.1 IP6.GATEWAY: 2001:db8:1::1 # nmcli -f GENERAL.CONNECTION,IP4.GATEWAY,IP6.GATEWAY device show enp7s0 GENERAL.CONNECTION: Internet-Provider IP4.GATEWAY: 198.51.100.1 IP6.GATEWAY: 2001:db8:2::1
In these examples, the profiles named
Corporate-LAN
andInternet-Provider
have the default gateways set. Because, in a local network, the default gateway is typically the host that is one hop closer to the internet, the rest of this procedure assumes that the default gateways in theCorporate-LAN
are incorrect.Configure that NetworkManager does not use the
Corporate-LAN
connection as the default route for IPv4 and IPv6 connections:# nmcli connection modify Corporate-LAN ipv4.never-default yes ipv6.never-default yes
Note that setting
ipv4.never-default
andipv6.never-default
toyes
, automatically removes the default gateway’s IP address for the corresponding protocol from the connection profile.Activate the
Corporate-LAN
connection:# nmcli connection up Corporate-LAN
Verification
Display the IPv4 and IPv6 routing tables and verify that only one default gateway is available for each protocol:
For IPv4, enter:
# ip -4 route default via 192.0.2.1 dev enp1s0 proto static metric 101 ...
For IPv6, enter:
# ip -6 route default via 2001:db8:1::1 dev enp1s0 proto static metric 101 pref medium ...
Additional resources
Chapter 24. Configuring a static route
Routing ensures that you can send and receive traffic between mutually-connected networks. In larger environments, administrators typically configure services so that routers can dynamically learn about other routers. In smaller environments, administrators often configure static routes to ensure that traffic can reach from one network to the next.
You need static routes to achieve a functioning communication among multiple networks if all of these conditions apply:
- The traffic has to pass multiple networks.
- The exclusive traffic flow through the default gateways is not sufficient.
The Example of a network that requires static routes section describes scenarios and how the traffic flows between different networks when you do not configure static routes.
24.1. Example of a network that requires static routes
You require static routes in this example because not all IP networks are directly connected through one router. Without the static routes, some networks cannot communicate with each other. Additionally, traffic from some networks flows only in one direction.
The network topology in this example is artificial and only used to explain the concept of static routing. It is not a recommended topology in production environments.
For a functioning communication among all networks in this example, configure a static route to Raleigh (198.51.100.0/24
) with next the hop Router 2 (203.0.113.10
). The IP address of the next hop is the one of Router 2 in the data center network (203.0.113.0/24
).
You can configure the static route as follows:
-
For a simplified configuration, set this static route only on Router 1. However, this increases the traffic on Router 1 because hosts from the data center (
203.0.113.0/24
) send traffic to Raleigh (198.51.100.0/24
) always through Router 1 to Router 2. -
For a more complex configuration, configure this static route on all hosts in the data center (
203.0.113.0/24
). All hosts in this subnet then send traffic directly to Router 2 (203.0.113.10
) that is closer to Raleigh (198.51.100.0/24
).
For more details between which networks traffic flows or not, see the explanations below the diagram.
![routing example](https://access.redhat.com/webassets/avalon/d/Red_Hat_Enterprise_Linux-8-Configuring_and_managing_networking-en-US/images/723cecf0994423cbfbdf04daff0df7ea/routing-example.png)
In case that the required static routes are not configured, the following are the situations in which the communication works and when it does not:
Hosts in the Berlin network (
192.0.2.0/24
):- Can communicate with other hosts in the same subnet because they are directly connected.
-
Can communicate with the internet because Router 1 is in the Berlin network (
192.0.2.0/24
) and has a default gateway, which leads to the internet. -
Can communicate with the data center network (
203.0.113.0/24
) because Router 1 has interfaces in both the Berlin (192.0.2.0/24
) and the data center (203.0.113.0/24
) networks. -
Cannot communicate with the Raleigh network (
198.51.100.0/24
) because Router 1 has no interface in this network. Therefore, Router 1 sends the traffic to its own default gateway (internet).
Hosts in the data center network (
203.0.113.0/24
):- Can communicate with other hosts in the same subnet because they are directly connected.
-
Can communicate with the internet because they have their default gateway set to Router 1, and Router 1 has interfaces in both networks, the data center (
203.0.113.0/24
) and to the internet. -
Can communicate with the Berlin network (
192.0.2.0/24
) because they have their default gateway set to Router 1, and Router 1 has interfaces in both the data center (203.0.113.0/24
) and the Berlin (192.0.2.0/24
) networks. -
Cannot communicate with the Raleigh network (
198.51.100.0/24
) because the data center network has no interface in this network. Therefore, hosts in the data center (203.0.113.0/24
) send traffic to their default gateway (Router 1). Router 1 also has no interface in the Raleigh network (198.51.100.0/24
) and, as a result, Router 1 sends this traffic to its own default gateway (internet).
Hosts in the Raleigh network (
198.51.100.0/24
):- Can communicate with other hosts in the same subnet because they are directly connected.
-
Cannot communicate with hosts on the internet. Router 2 sends the traffic to Router 1 because of the default gateway settings. The actual behavior of Router 1 depends on the reverse path filter (
rp_filter
) system control (sysctl
) setting. By default on RHEL, Router 1 drops the outgoing traffic instead of routing it to the internet. However, regardless of the configured behavior, communication is not possible without the static route. -
Cannot communicate with the data center network (
203.0.113.0/24
). The outgoing traffic reaches the destination through Router 2 because of the default gateway setting. However, replies to packets do not reach the sender because hosts in the data center network (203.0.113.0/24
) send replies to their default gateway (Router 1). Router 1 then sends the traffic to the internet. -
Cannot communicate with the Berlin network (
192.0.2.0/24
). Router 2 sends the traffic to Router 1 because of the default gateway settings. The actual behavior of Router 1 depends on therp_filter
sysctl
setting. By default on RHEL, Router 1 drops the outgoing traffic instead of sending it to the Berlin network (192.0.2.0/24
). However, regardless of the configured behavior, communication is not possible without the static route.
In addition to configuring the static routes, you must enable IP forwarding on both routers.
24.2. How to use the nmcli
utility to configure a static route
To configure a static route, use the nmcli
utility with the following syntax:
$ nmcli connection modify connection_name ipv4.routes "ip[/prefix] [next_hop] [metric] [attribute=value] [attribute=value] ..."
The command supports the following route attributes:
-
cwnd=n
: Sets the congestion window (CWND) size, defined in number of packets. -
lock-cwnd=true|false
: Defines whether or not the kernel can update the CWND value. -
lock-mtu=true|false
: Defines whether or not the kernel can update the MTU to path MTU discovery. -
lock-window=true|false
: Defines whether or not the kernel can update the maximum window size for TCP packets. -
mtu=<mtu_value>
: Sets the maximum transfer unit (MTU) to use along the path to the destination. -
onlink=true|false
: Defines whether the next hop is directly attached to this link even if it does not match any interface prefix. -
scope=<scope>
: For an IPv4 route, this attribute sets the scope of the destinations covered by the route prefix. Set the value as an integer (0-255). -
src=<source_address>
: Sets the source address to prefer when sending traffic to the destinations covered by the route prefix. -
table=<table_id>
: Sets the ID of the table the route should be added to. If you omit this parameter, NetworkManager uses themain
table. -
tos=<type_of_service_key>
: Sets the type of service (TOS) key. Set the value as an integer (0-255). -
type=<route_type>
: Sets the route type. NetworkManager supports theunicast
,local
,blackhole
,unreachable
,prohibit
, andthrow
route types. The default isunicast
. -
window=<window_size>
: Sets the maximal window size for TCP to advertise to these destinations, measured in bytes.
If you use the ipv4.routes
option without a preceding +
sign, nmcli
overrides all current settings of this parameter.
To create an additional route, enter:
$ nmcli connection modify connection_name +ipv4.routes "<route>"
To remove a specific route, enter:
$ nmcli connection modify connection_name -ipv4.routes "<route>"
24.3. Configuring a static route by using nmcli
You can add a static route to an existing NetworkManager connection profile using the nmcli connection modify
command.
The procedure below configures the following routes:
-
An IPv4 route to the remote
198.51.100.0/24
network. The corresponding gateway with the IP address192.0.2.10
is reachable through theLAN
connection profile. -
An IPv6 route to the remote
2001:db8:2::/64
network. The corresponding gateway with the IP address2001:db8:1::10
is reachable through theLAN
connection profile.
Prerequisites
-
The
LAN
connection profile exists and it configures this host to be in the same IP subnet as the gateways.
Procedure
Add the static IPv4 route to the
LAN
connection profile:# nmcli connection modify LAN +ipv4.routes "198.51.100.0/24 192.0.2.10"
To set multiple routes in one step, pass the individual routes comma-separated to the command:
# nmcli connection modify <connection_profile> +ipv4.routes "<remote_network_1>/<subnet_mask_1> <gateway_1>, <remote_network_n>/<subnet_mask_n> <gateway_n>, ..."
Add the static IPv6 route to the
LAN
connection profile:# nmcli connection modify LAN +ipv6.routes "2001:db8:2::/64 2001:db8:1::10"
Re-activate the connection:
# nmcli connection up LAN
Verification
Display the IPv4 routes:
# ip -4 route ... 198.51.100.0/24 via 192.0.2.10 dev enp1s0
Display the IPv6 routes:
# ip -6 route ... 2001:db8:2::/64 via 2001:db8:1::10 dev enp1s0 metric 1024 pref medium
24.4. Configuring a static route by using nmtui
The nmtui
application provides a text-based user interface for NetworkManager. You can use nmtui
to configure static routes on a host without a graphical interface.
For example, the procedure below adds a route to the 192.0.2.0/24
network that uses the gateway running on 198.51.100.1
, which is reachable through an existing connection profile.
In nmtui
:
- Navigate by using the cursor keys.
- Press a button by selecting it and hitting Enter.
- Select and clear checkboxes by using Space.
Prerequisites
- The network is configured.
- The gateway for the static route must be directly reachable on the interface.
- If the user is logged in on a physical console, user permissions are sufficient. Otherwise, the command requires root permissions.
Procedure
Start
nmtui
:# nmtui
- Select Edit a connection, and press Enter.
- Select the connection profile through which you can reach the next hop to the destination network, and press Enter.
- Depending on whether it is an IPv4 or IPv6 route, press the Show button next to the protocol’s configuration area.
Press the Edit button next to Routing. This opens a new window where you configure static routes:
Press the Add button and fill in:
- The destination network, including the prefix in Classless Inter-Domain Routing (CIDR) format
- The IP address of the next hop
- A metric value, if you add multiple routes to the same network and want to prioritize the routes by efficiency
- Repeat the previous step for every route you want to add and that is reachable through this connection profile.
Press the OK button to return to the window with the connection settings.
Figure 24.1. Example of a static route without metric
-
Press the OK button to return to the
nmtui
main menu. - Select Activate a connection and press Enter.
Select the connection profile that you edited, and press Enter twice to deactivate and activate it again.
ImportantSkip this step if you run
nmtui
over a remote connection, such as SSH, that uses the connection profile you want to reactivate. In this case, if you would deactivate it innmtui
, the connection is terminated and, consequently, you cannot activate it again. To avoid this problem, use thenmcli connection <connection_profile> up
command to reactivate the connection in the mentioned scenario.- Press the Back button to return to the main menu.
-
Select Quit, and press Enter to close the
nmtui
application.
Verification
Verify that the route is active:
$ ip route ... 192.0.2.0/24 via 198.51.100.1 dev example proto static metric 100
24.5. Configuring a static route by using control-center
You can use control-center
in GNOME to add a static route to the configuration of a network connection.
The procedure below configures the following routes:
-
An IPv4 route to the remote
198.51.100.0/24
network. The corresponding gateway has the IP address192.0.2.10
. -
An IPv6 route to the remote
2001:db8:2::/64
network. The corresponding gateway has the IP address2001:db8:1::10
.
Prerequisites
- The network is configured.
- This host is in the same IP subnet as the gateways.
-
The network configuration of the connection is opened in the
control-center
application. See Configuring an Ethernet connection by using nm-connection-editor.
Procedure
On the
IPv4
tab:-
Optional: Disable automatic routes by clicking the
Routes
section of theIPv4
tab to use only static routes. If automatic routes are enabled, Red Hat Enterprise Linux uses static routes and routes received from a DHCP server. button in the Enter the address, netmask, gateway, and optionally a metric value of the IPv4 route:
-
Optional: Disable automatic routes by clicking the
On the
IPv6
tab:-
Optional: Disable automatic routes by clicking the
Routes
section of theIPv4
tab to use only static routes. button i the Enter the address, netmask, gateway, and optionally a metric value of the IPv6 route:
-
Optional: Disable automatic routes by clicking the
- Click .
Back in the
Network
window, disable and re-enable the connection by switching the button for the connection to and back to for changes to take effect.WarningRestarting the connection briefly disrupts connectivity on that interface.
Verification
Display the IPv4 routes:
# ip -4 route ... 198.51.100.0/24 via 192.0.2.10 dev enp1s0
Display the IPv6 routes:
# ip -6 route ... 2001:db8:2::/64 via 2001:db8:1::10 dev enp1s0 metric 1024 pref medium
24.6. Configuring a static route by using nm-connection-editor
You can use the nm-connection-editor
application to add a static route to the configuration of a network connection.
The procedure below configures the following routes:
-
An IPv4 route to the remote
198.51.100.0/24
network. The corresponding gateway with the IP address192.0.2.10
is reachable through theexample
connection. -
An IPv6 route to the remote
2001:db8:2::/64
network. The corresponding gateway with the IP address2001:db8:1::10
is reachable through theexample
connection.
Prerequisites
- The network is configured.
- This host is in the same IP subnet as the gateways.
Procedure
Open a terminal, and enter
nm-connection-editor
:$ nm-connection-editor
-
Select the
example
connection profile, and click the gear wheel icon to edit the existing connection. On the
IPv4 Settings
tab:- Click the button.
Click the
button and enter the address, netmask, gateway, and optionally a metric value.- Click .
On the
IPv6 Settings
tab:- Click the button.
Click the
button and enter the address, netmask, gateway, and optionally a metric value.- Click .
- Click .
Restart the network connection for changes to take effect. For example, to restart the
example
connection using the command line:# nmcli connection up example
Verification
Display the IPv4 routes:
# ip -4 route ... 198.51.100.0/24 via 192.0.2.10 dev enp1s0
Display the IPv6 routes:
# ip -6 route ... 2001:db8:2::/64 via 2001:db8:1::10 dev enp1s0 metric 1024 pref medium
24.7. Configuring a static route by using the nmcli
interactive mode
You can use the interactive mode of the nmcli
utility to add a static route to the configuration of a network connection.
The procedure below configures the following routes:
-
An IPv4 route to the remote
198.51.100.0/24
network. The corresponding gateway with the IP address192.0.2.10
is reachable through theexample
connection. -
An IPv6 route to the remote
2001:db8:2::/64
network. The corresponding gateway with the IP address2001:db8:1::10
is reachable through theexample
connection.
Prerequisites
-
The
example
connection profile exists and it configures this host to be in the same IP subnet as the gateways.
Procedure
Open the
nmcli
interactive mode for theexample
connection:# nmcli connection edit example
Add the static IPv4 route:
nmcli> set ipv4.routes 198.51.100.0/24 192.0.2.10
Add the static IPv6 route:
nmcli> set ipv6.routes 2001:db8:2::/64 2001:db8:1::10
Optional: Verify that the routes were added correctly to the configuration:
nmcli> print ... ipv4.routes: { ip = 198.51.100.0/24, nh = 192.0.2.10 } ... ipv6.routes: { ip = 2001:db8:2::/64, nh = 2001:db8:1::10 } ...
The
ip
attribute displays the network to route and thenh
attribute the gateway (next hop).Save the configuration:
nmcli> save persistent
Restart the network connection:
nmcli> activate example
Leave the
nmcli
interactive mode:nmcli> quit
Verification
Display the IPv4 routes:
# ip -4 route ... 198.51.100.0/24 via 192.0.2.10 dev enp1s0
Display the IPv6 routes:
# ip -6 route ... 2001:db8:2::/64 via 2001:db8:1::10 dev enp1s0 metric 1024 pref medium
Additional resources
-
nmcli(1)
man page -
nm-settings-nmcli(5)
man page
24.8. Configuring a static route by using nmstatectl
Use the nmstatectl
utility to configure a static route through the Nmstate API. The Nmstate API ensures that, after setting the configuration, the result matches the configuration file. If anything fails, nmstatectl
automatically rolls back the changes to avoid leaving the system in an incorrect state.
Prerequisites
-
The
enp1s0
network interface is configured and is in the same IP subnet as the gateways. -
The
nmstate
package is installed.
Procedure
Create a YAML file, for example
~/add-static-route-to-enp1s0.yml
, with the following content:--- routes: config: - destination: 198.51.100.0/24 next-hop-address: 192.0.2.10 next-hop-interface: enp1s0 - destination: 2001:db8:2::/64 next-hop-address: 2001:db8:1::10 next-hop-interface: enp1s0
These settings define the following static routes:
-
An IPv4 route to the remote
198.51.100.0/24
network. The corresponding gateway with the IP address192.0.2.10
is reachable through theenp1s0
interface. -
An IPv6 route to the remote
2001:db8:2::/64
network. The corresponding gateway with the IP address2001:db8:1::10
is reachable through theenp1s0
interface.
-
An IPv4 route to the remote
Apply the settings to the system:
# nmstatectl apply ~/add-static-route-to-enp1s0.yml
Verification
Display the IPv4 routes:
# ip -4 route ... 198.51.100.0/24 via 192.0.2.10 dev enp1s0
Display the IPv6 routes:
# ip -6 route ... 2001:db8:2::/64 via 2001:db8:1::10 dev enp1s0 metric 1024 pref medium
Additional resources
-
nmstatectl(8)
man page -
/usr/share/doc/nmstate/examples/
directory
24.9. Configuring a static route by using the network
RHEL system role
A static route ensures that you can send traffic to a destination that cannot be reached through the default gateway. You configure static routes in the NetworkManager connection profile of the interface that is connected to the same network as the next hop. By using Ansible and the network
RHEL system role, you can automate this process and remotely configure connection profiles on the hosts defined in a playbook.
You cannot use the network
RHEL system role to update only specific values in an existing connection profile. The role ensures that a connection profile exactly matches the settings in a playbook. If a connection profile with the same name already exists, the role applies the settings from the playbook and resets all other settings in the profile to their defaults. To prevent resetting values, always specify the whole configuration of the network connection profile in the playbook, including the settings that you do not want to change.
Prerequisites
- You have prepared the control node and the managed nodes
- You are logged in to the control node as a user who can run playbooks on the managed nodes.
-
The account you use to connect to the managed nodes has
sudo
permissions on them.
Procedure
Create a playbook file, for example
~/playbook.yml
, with the following content:--- - name: Configure the network hosts: managed-node-01.example.com tasks: - name: Ethernet connection profile with static IP address settings ansible.builtin.include_role: name: rhel-system-roles.network vars: network_connections: - name: enp7s0 type: ethernet autoconnect: yes ip: address: - 192.0.2.1/24 - 2001:db8:1::1/64 gateway4: 192.0.2.254 gateway6: 2001:db8:1::fffe dns: - 192.0.2.200 - 2001:db8:1::ffbb dns_search: - example.com route: - network: 198.51.100.0 prefix: 24 gateway: 192.0.2.10 - network: 2001:db8:2:: prefix: 64 gateway: 2001:db8:1::10 state: up
For details about all variables used in the playbook, see the
/usr/share/ansible/roles/rhel-system-roles.network/README.md
file on the control node.Validate the playbook syntax:
$ ansible-playbook --syntax-check ~/playbook.yml
Note that this command only validates the syntax and does not protect against a wrong but valid configuration.
Run the playbook:
$ ansible-playbook ~/playbook.yml
Verification
Display the IPv4 routes:
# ansible managed-node-01.example.com -m command -a 'ip -4 route' managed-node-01.example.com | CHANGED | rc=0 >> ... 198.51.100.0/24 via 192.0.2.10 dev enp7s0
Display the IPv6 routes:
# ansible managed-node-01.example.com -m command -a 'ip -6 route' managed-node-01.example.com | CHANGED | rc=0 >> ... 2001:db8:2::/64 via 2001:db8:1::10 dev enp7s0 metric 1024 pref medium
Additional resources
-
/usr/share/ansible/roles/rhel-system-roles.network/README.md
file -
/usr/share/doc/rhel-system-roles/network/
directory
24.10. Creating static routes configuration files in key-value format when using the legacy network scripts
The legacy network scripts support setting statics routes in key-value format.
The procedure below configures an IPv4 route to the remote 198.51.100.0/24
network. The corresponding gateway with the IP address 192.0.2.10
is reachable through the enp1s0
interface.
The legacy network scripts support the key-value format only for static IPv4 routes. For IPv6 routes, use the ip
-command format. See Creating static routes configuration files in ip-command format when using the legacy network scripts.
Prerequisites
- The gateways for the static route must be directly reachable on the interface.
-
The
NetworkManager
package is not installed, or theNetworkManager
service is disabled. -
The
network-scripts
package is installed. -
The
network
service is enabled.
Procedure
Add the static IPv4 route to the
/etc/sysconfig/network-scripts/route-enp0s1
file:ADDRESS0=198.51.100.0 NETMASK0=255.255.255.0 GATEWAY0=192.0.2.10
-
The
ADDRESS0
variable defines the network of the first routing entry. -
The
NETMASK0
variable defines the netmask of the first routing entry. The
GATEWAY0
variable defines the IP address of the gateway to the remote network or host for the first routing entry.If you add multiple static routes, increase the number in the variable names. Note that the variables for each route must be numbered sequentially. For example,
ADDRESS0
,ADDRESS1
,ADDRESS3
, and so on.
-
The
Restart the network:
# systemctl restart network
Verification
Display the IPv4 routes:
# ip -4 route ... 198.51.100.0/24 via 192.0.2.10 dev enp1s0
Troubleshooting
Display the journal entries of the
network
unit:# journalctl -u network
The following are possible error messages and their causes:
-
Error: Nexthop has invalid gateway
: You specified an IPv4 gateway address in theroute-enp1s0
file that is not in the same subnet as this router. -
RTNETLINK answers: No route to host
: You specified an IPv6 gateway address in theroute6-enp1s0
file that is not in the same subnet as this router. -
Error: Invalid prefix for given prefix length
: You specified the remote network in theroute-enp1s0
file by using an IP address within the remote network rather than the network address.
-
Additional resources
-
/usr/share/doc/network-scripts/sysconfig.txt
file
24.11. Creating static routes configuration files in ip-command format when using the legacy network scripts
The legacy network scripts support setting statics routes.
The procedure below configures the following routes:
-
An IPv4 route to the remote
198.51.100.0/24
network. The corresponding gateway with the IP address192.0.2.10
is reachable through theenp1s0
interface. -
An IPv6 route to the remote
2001:db8:2::/64
network. The corresponding gateway with the IP address2001:db8:1::10
is reachable through theenp1s0
interface.
IP addresses of the gateways (next hop) must be in the same IP subnet as the host on which you configure the static routes.
The examples in this procedure use configuration entries in ip
-command format.
Prerequisites
- The gateways for the static route must be directly reachable on the interface.
-
The
NetworkManager
package is not installed, or theNetworkManager
service is disabled. -
The
network-scripts
package is installed. -
The
network
service is enabled.
Procedure
Add the static IPv4 route to the
/etc/sysconfig/network-scripts/route-enp1s0
file:198.51.100.0/24 via 192.0.2.10 dev enp1s0
Always specify the network address of the remote network, such as
198.51.100.0
. Setting an IP address within the remote network, such as198.51.100.1
causes that the network scripts fail to add this route.Add the static IPv6 route to the
/etc/sysconfig/network-scripts/route6-enp1s0
file:2001:db8:2::/64 via 2001:db8:1::10 dev enp1s0
Restart the
network
service:# systemctl restart network
Verification
Display the IPv4 routes:
# ip -4 route ... 198.51.100.0/24 via 192.0.2.10 dev enp1s0
Display the IPv6 routes:
# ip -6 route ... 2001:db8:2::/64 via 2001:db8:1::10 dev enp1s0 metric 1024 pref medium
Troubleshooting
Display the journal entries of the
network
unit:# journalctl -u network
The following are possible error messages and their causes:
-
Error: Nexthop has invalid gateway
: You specified an IPv4 gateway address in theroute-enp1s0
file that is not in the same subnet as this router. -
RTNETLINK answers: No route to host
: You specified an IPv6 gateway address in theroute6-enp1s0
file that is not in the same subnet as this router. -
Error: Invalid prefix for given prefix length
: You specified the remote network in theroute-enp1s0
file by using an IP address within the remote network rather than the network address.
-
Additional Resources
-
/usr/share/doc/network-scripts/sysconfig.txt
file
Chapter 25. Configuring policy-based routing to define alternative routes
By default, the kernel in RHEL decides where to forward network packets based on the destination address using a routing table. Policy-based routing enables you to configure complex routing scenarios. For example, you can route packets based on various criteria, such as the source address, packet metadata, or protocol.
25.1. Routing traffic from a specific subnet to a different default gateway by using nmcli
You can use policy-based routing to configure a different default gateway for traffic from certain subnets. For example, you can configure RHEL as a router that, by default, routes all traffic to internet provider A using the default route. However, traffic received from the internal workstations subnet is routed to provider B.
The procedure assumes the following network topology:
Prerequisites
-
The system uses
NetworkManager
to configure the network, which is the default. The RHEL router you want to set up in the procedure has four network interfaces:
-
The
enp7s0
interface is connected to the network of provider A. The gateway IP in the provider’s network is198.51.100.2
, and the network uses a/30
network mask. -
The
enp1s0
interface is connected to the network of provider B. The gateway IP in the provider’s network is192.0.2.2
, and the network uses a/30
network mask. -
The
enp8s0
interface is connected to the10.0.0.0/24
subnet with internal workstations. -
The
enp9s0
interface is connected to the203.0.113.0/24
subnet with the company’s servers.
-
The
-
Hosts in the internal workstations subnet use
10.0.0.1
as the default gateway. In the procedure, you assign this IP address to theenp8s0
network interface of the router. -
Hosts in the server subnet use
203.0.113.1
as the default gateway. In the procedure, you assign this IP address to theenp9s0
network interface of the router. -
The
firewalld
service is enabled and active.
Procedure
Configure the network interface to provider A:
# nmcli connection add type ethernet con-name Provider-A ifname enp7s0 ipv4.method manual ipv4.addresses 198.51.100.1/30 ipv4.gateway 198.51.100.2 ipv4.dns 198.51.100.200 connection.zone external
The
nmcli connection add
command creates a NetworkManager connection profile. The command uses the following options:-
type
ethernet
: Defines that the connection type is Ethernet. -
con-name
<connection_name>
: Sets the name of the profile. Use a meaningful name to avoid confusion. -
ifname
<network_device>
: Sets the network interface. -
ipv4.method
manual
: Enables to configure a static IP address. -
ipv4.addresses
<IP_address>/<subnet_mask>
: Sets the IPv4 addresses and subnet mask. -
ipv4.gateway
<IP_address>
: Sets the default gateway address. -
ipv4.dns
<IP_of_DNS_server>
: Sets the IPv4 address of the DNS server. -
connection.zone
<firewalld_zone>
: Assigns the network interface to the definedfirewalld
zone. Note thatfirewalld
automatically enables masquerading for interfaces assigned to theexternal
zone.
-
Configure the network interface to provider B:
# nmcli connection add type ethernet con-name Provider-B ifname enp1s0 ipv4.method manual ipv4.addresses 192.0.2.1/30 ipv4.routes "0.0.0.0/0 192.0.2.2 table=5000" connection.zone external
This command uses the
ipv4.routes
parameter instead ofipv4.gateway
to set the default gateway. This is required to assign the default gateway for this connection to a different routing table (5000
) than the default. NetworkManager automatically creates this new routing table when the connection is activated.Configure the network interface to the internal workstations subnet:
# nmcli connection add type ethernet con-name Internal-Workstations ifname enp8s0 ipv4.method manual ipv4.addresses 10.0.0.1/24 ipv4.routes "10.0.0.0/24 table=5000" ipv4.routing-rules "priority 5 from 10.0.0.0/24 table 5000" connection.zone trusted
This command uses the
ipv4.routes
parameter to add a static route to the routing table with ID5000
. This static route for the10.0.0.0/24
subnet uses the IP of the local network interface to provider B (192.0.2.1
) as next hop.Additionally, the command uses the
ipv4.routing-rules
parameter to add a routing rule with priority5
that routes traffic from the10.0.0.0/24
subnet to table5000
. Low values have a high priority.Note that the syntax in the
ipv4.routing-rules
parameter is the same as in anip rule add
command, except thatipv4.routing-rules
always requires specifying a priority.Configure the network interface to the server subnet:
# nmcli connection add type ethernet con-name Servers ifname enp9s0 ipv4.method manual ipv4.addresses 203.0.113.1/24 connection.zone trusted
Verification
On a RHEL host in the internal workstation subnet:
Install the
traceroute
package:# yum install traceroute
Use the
traceroute
utility to display the route to a host on the internet:# traceroute redhat.com traceroute to redhat.com (209.132.183.105), 30 hops max, 60 byte packets 1 10.0.0.1 (10.0.0.1) 0.337 ms 0.260 ms 0.223 ms 2 192.0.2.1 (192.0.2.1) 0.884 ms 1.066 ms 1.248 ms ...
The output of the command displays that the router sends packets over
192.0.2.1
, which is the network of provider B.
On a RHEL host in the server subnet:
Install the
traceroute
package:# yum install traceroute
Use the
traceroute
utility to display the route to a host on the internet:# traceroute redhat.com traceroute to redhat.com (209.132.183.105), 30 hops max, 60 byte packets 1 203.0.113.1 (203.0.113.1) 2.179 ms 2.073 ms 1.944 ms 2 198.51.100.2 (198.51.100.2) 1.868 ms 1.798 ms 1.549 ms ...
The output of the command displays that the router sends packets over
198.51.100.2
, which is the network of provider A.
Troubleshooting steps
On the RHEL router:
Display the rule list:
# ip rule list 0: from all lookup local 5: from 10.0.0.0/24 lookup 5000 32766: from all lookup main 32767: from all lookup default
By default, RHEL contains rules for the tables
local
,main
, anddefault
.Display the routes in table
5000
:# ip route list table 5000 0.0.0.0/0 via 192.0.2.2 dev enp1s0 proto static metric 100 10.0.0.0/24 dev enp8s0 proto static scope link src 192.0.2.1 metric 102
Display the interfaces and firewall zones:
# firewall-cmd --get-active-zones external interfaces: enp1s0 enp7s0 trusted interfaces: enp8s0 enp9s0
Verify that the
external
zone has masquerading enabled:# firewall-cmd --info-zone=external external (active) target: default icmp-block-inversion: no interfaces: enp1s0 enp7s0 sources: services: ssh ports: protocols: masquerade: yes ...
Additional resources
-
nm-settings(5)
man page -
nmcli(1)
man page
25.2. Routing traffic from a specific subnet to a different default gateway by using the network
RHEL system role
You can use policy-based routing to configure a different default gateway for traffic from certain subnets. For example, you can configure RHEL as a router that, by default, routes all traffic to internet provider A using the default route. However, traffic received from the internal workstations subnet is routed to provider B. By using Ansible and the network
RHEL system role, you can automate this process and remotely configure connection profiles on the hosts defined in a playbook.
You can use the network
RHEL system role to configure the connection profiles, including routing tables and rules.
This procedure assumes the following network topology:
Prerequisites
- You have prepared the control node and the managed nodes
- You are logged in to the control node as a user who can run playbooks on the managed nodes.
-
The account you use to connect to the managed nodes has
sudo
permissions on them. -
The managed nodes uses the
NetworkManager
andfirewalld
services. The managed nodes you want to configure has four network interfaces:
-
The
enp7s0
interface is connected to the network of provider A. The gateway IP in the provider’s network is198.51.100.2
, and the network uses a/30
network mask. -
The
enp1s0
interface is connected to the network of provider B. The gateway IP in the provider’s network is192.0.2.2
, and the network uses a/30
network mask. -
The
enp8s0
interface is connected to the10.0.0.0/24
subnet with internal workstations. -
The
enp9s0
interface is connected to the203.0.113.0/24
subnet with the company’s servers.
-
The
-
Hosts in the internal workstations subnet use
10.0.0.1
as the default gateway. In the procedure, you assign this IP address to theenp8s0
network interface of the router. -
Hosts in the server subnet use
203.0.113.1
as the default gateway. In the procedure, you assign this IP address to theenp9s0
network interface of the router.
Procedure
Create a playbook file, for example
~/playbook.yml
, with the following content:--- - name: Configuring policy-based routing hosts: managed-node-01.example.com tasks: - name: Routing traffic from a specific subnet to a different default gateway ansible.builtin.include_role: name: rhel-system-roles.network vars: network_connections: - name: Provider-A interface_name: enp7s0 type: ethernet autoconnect: True ip: address: - 198.51.100.1/30 gateway4: 198.51.100.2 dns: - 198.51.100.200 state: up zone: external - name: Provider-B interface_name: enp1s0 type: ethernet autoconnect: True ip: address: - 192.0.2.1/30 route: - network: 0.0.0.0 prefix: 0 gateway: 192.0.2.2 table: 5000 state: up zone: external - name: Internal-Workstations interface_name: enp8s0 type: ethernet autoconnect: True ip: address: - 10.0.0.1/24 route: - network: 10.0.0.0 prefix: 24 table: 5000 routing_rule: - priority: 5 from: 10.0.0.0/24 table: 5000 state: up zone: trusted - name: Servers interface_name: enp9s0 type: ethernet autoconnect: True ip: address: - 203.0.113.1/24 state: up zone: trusted
The settings specified in the example playbook include the following:
table: <value>
-
Assigns the route from the same list entry as the
table
variable to the specified routing table. routing_rule: <list>
- Defines the priority of the specified routing rule and from a connection profile to which routing table the rule is assigned.
zone: <zone_name>
-
Assigns the network interface from a connection profile to the specified
firewalld
zone.
For details about all variables used in the playbook, see the
/usr/share/ansible/roles/rhel-system-roles.network/README.md
file on the control node.Validate the playbook syntax:
$ ansible-playbook --syntax-check ~/playbook.yml
Note that this command only validates the syntax and does not protect against a wrong but valid configuration.
Run the playbook:
$ ansible-playbook ~/playbook.yml
Verification
On a RHEL host in the internal workstation subnet:
Install the
traceroute
package:# yum install traceroute
Use the
traceroute
utility to display the route to a host on the internet:# traceroute redhat.com traceroute to redhat.com (209.132.183.105), 30 hops max, 60 byte packets 1 10.0.0.1 (10.0.0.1) 0.337 ms 0.260 ms 0.223 ms 2 192.0.2.1 (192.0.2.1) 0.884 ms 1.066 ms 1.248 ms ...
The output of the command displays that the router sends packets over
192.0.2.1
, which is the network of provider B.
On a RHEL host in the server subnet:
Install the
traceroute
package:# yum install traceroute
Use the
traceroute
utility to display the route to a host on the internet:# traceroute redhat.com traceroute to redhat.com (209.132.183.105), 30 hops max, 60 byte packets 1 203.0.113.1 (203.0.113.1) 2.179 ms 2.073 ms 1.944 ms 2 198.51.100.2 (198.51.100.2) 1.868 ms 1.798 ms 1.549 ms ...
The output of the command displays that the router sends packets over
198.51.100.2
, which is the network of provider A.
On the RHEL router that you configured using the RHEL system role:
Display the rule list:
# ip rule list 0: from all lookup local 5: from 10.0.0.0/24 lookup 5000 32766: from all lookup main 32767: from all lookup default
By default, RHEL contains rules for the tables
local
,main
, anddefault
.Display the routes in table
5000
:# ip route list table 5000 0.0.0.0/0 via 192.0.2.2 dev enp1s0 proto static metric 100 10.0.0.0/24 dev enp8s0 proto static scope link src 192.0.2.1 metric 102
Display the interfaces and firewall zones:
# firewall-cmd --get-active-zones external interfaces: enp1s0 enp7s0 trusted interfaces: enp8s0 enp9s0
Verify that the
external
zone has masquerading enabled:# firewall-cmd --info-zone=external external (active) target: default icmp-block-inversion: no interfaces: enp1s0 enp7s0 sources: services: ssh ports: protocols: masquerade: yes ...
Additional resources
-
/usr/share/ansible/roles/rhel-system-roles.network/README.md
file -
/usr/share/doc/rhel-system-roles/network/
directory
25.3. Overview of configuration files involved in policy-based routing when using the legacy network scripts
If you use the legacy network scripts instead of NetworkManager to configure your network, you can also configure policy-based routing.
Configuring the network using the legacy network scripts provided by the network-scripts
package is deprecated in RHEL 8. Use NetworkManager to configure policy-based routing. For an example, see Routing traffic from a specific subnet to a different default gateway by using nmcli.
The following configuration files are involved in policy-based routing when you use the legacy network scripts:
/etc/sysconfig/network-scripts/route-interface
: This file defines the IPv4 routes. Use thetable
option to specify the routing table. For example:192.0.2.0/24 via 198.51.100.1 table 1 203.0.113.0/24 via 198.51.100.2 table 2
-
/etc/sysconfig/network-scripts/route6-interface
: This file defines the IPv6 routes. /etc/sysconfig/network-scripts/rule-interface
: This file defines the rules for IPv4 source networks for which the kernel routes traffic to specific routing tables. For example:from 192.0.2.0/24 lookup 1 from 203.0.113.0/24 lookup 2
-
/etc/sysconfig/network-scripts/rule6-interface
: This file defines the rules for IPv6 source networks for which the kernel routes traffic to specific routing tables. /etc/iproute2/rt_tables
: This file defines the mappings if you want to use names instead of numbers to refer to specific routing tables. For example:1 Provider_A 2 Provider_B
Additional resources
-
ip-route(8)
man page -
ip-rule(8)
man page
25.4. Routing traffic from a specific subnet to a different default gateway by using the legacy network scripts
You can use policy-based routing to configure a different default gateway for traffic from certain subnets. For example, you can configure RHEL as a router that, by default, routes all traffic to internet provider A using the default route. However, traffic received from the internal workstations subnet is routed to provider B.
Configuring the network using the legacy network scripts provided by the network-scripts
package is deprecated in RHEL 8. Follow the procedure only if you use the legacy network scripts instead of NetworkManager on your host. If you use NetworkManager to manage your network settings, see Routing traffic from a specific subnet to a different default gateway by using nmcli.
The procedure assumes the following network topology:
The legacy network scripts process configuration files in alphabetical order. Therefore, you must name the configuration files in a way that ensures that an interface, that is used in rules and routes of other interfaces, are up when a depending interface requires it. To accomplish the correct order, this procedure uses numbers in the ifcfg-*
, route-*
, and rules-*
files.
Prerequisites
-
The
NetworkManager
package is not installed, or theNetworkManager
service is disabled. -
The
network-scripts
package is installed. The RHEL router you want to set up in the procedure has four network interfaces:
-
The
enp7s0
interface is connected to the network of provider A. The gateway IP in the provider’s network is198.51.100.2
, and the network uses a/30
network mask. -
The
enp1s0
interface is connected to the network of provider B. The gateway IP in the provider’s network is192.0.2.2
, and the network uses a/30
network mask. -
The
enp8s0
interface is connected to the10.0.0.0/24
subnet with internal workstations. -
The
enp9s0
interface is connected to the203.0.113.0/24
subnet with the company’s servers.
-
The
-
Hosts in the internal workstations subnet use
10.0.0.1
as the default gateway. In the procedure, you assign this IP address to theenp8s0
network interface of the router. -
Hosts in the server subnet use
203.0.113.1
as the default gateway. In the procedure, you assign this IP address to theenp9s0
network interface of the router. -
The
firewalld
service is enabled and active.
Procedure
Add the configuration for the network interface to provider A by creating the
/etc/sysconfig/network-scripts/ifcfg-1_Provider-A
file with the following content:TYPE=Ethernet IPADDR=198.51.100.1 PREFIX=30 GATEWAY=198.51.100.2 DNS1=198.51.100.200 DEFROUTE=yes NAME=1_Provider-A DEVICE=enp7s0 ONBOOT=yes ZONE=external
The configuration file uses the following parameters:
-
TYPE
=Ethernet
: Defines that the connection type is Ethernet. -
IPADDR
=IP_address
: Sets the IPv4 address. -
PREFIX
=subnet_mask
: Sets the subnet mask. -
GATEWAY
=IP_address
: Sets the default gateway address. -
DNS1
=IP_of_DNS_server
: Sets the IPv4 address of the DNS server. -
DEFROUTE
=yes|no
: Defines whether the connection is a default route or not. -
NAME
=connection_name
: Sets the name of the connection profile. Use a meaningful name to avoid confusion. -
DEVICE
=network_device
: Sets the network interface. -
ONBOOT
=yes
: Defines that RHEL starts this connection when the system boots. -
ZONE
=firewalld_zone
: Assigns the network interface to the definedfirewalld
zone. Note thatfirewalld
automatically enables masquerading for interfaces assigned to theexternal
zone.
-
Add the configuration for the network interface to provider B:
Create the
/etc/sysconfig/network-scripts/ifcfg-2_Provider-B
file with the following content:TYPE=Ethernet IPADDR=192.0.2.1 PREFIX=30 DEFROUTE=no NAME=2_Provider-B DEVICE=enp1s0 ONBOOT=yes ZONE=external
Note that the configuration file for this interface does not contain a default gateway setting.
Assign the gateway for the
2_Provider-B
connection to a separate routing table. Therefore, create the/etc/sysconfig/network-scripts/route-2_Provider-B
file with the following content:0.0.0.0/0 via 192.0.2.2 table 5000
This entry assigns the gateway and traffic from all subnets routed through this gateway to table
5000.
Create the configuration for the network interface to the internal workstations subnet:
Create the
/etc/sysconfig/network-scripts/ifcfg-3_Internal-Workstations
file with the following content:TYPE=Ethernet IPADDR=10.0.0.1 PREFIX=24 DEFROUTE=no NAME=3_Internal-Workstations DEVICE=enp8s0 ONBOOT=yes ZONE=internal
Add the routing rule configuration for the internal workstation subnet. Therefore, create the
/etc/sysconfig/network-scripts/rule-3_Internal-Workstations
file with the following content:pri 5 from 10.0.0.0/24 table 5000
This configuration defines a routing rule with priority
5
that routes all traffic from the10.0.0.0/24
subnet to table5000
. Low values have a high priority.Create the
/etc/sysconfig/network-scripts/route-3_Internal-Workstations
file with the following content to add a static route to the routing table with ID5000
:10.0.0.0/24 via 192.0.2.1 table 5000
This static route defines that RHEL sends traffic from the
10.0.0.0/24
subnet to the IP of the local network interface to provider B (192.0.2.1
). This interface is to routing table5000
and used as the next hop.
Add the configuration for the network interface to the server subnet by creating the
/etc/sysconfig/network-scripts/ifcfg-4_Servers
file with the following content:TYPE=Ethernet IPADDR=203.0.113.1 PREFIX=24 DEFROUTE=no NAME=4_Servers DEVICE=enp9s0 ONBOOT=yes ZONE=internal
Restart the network:
# systemctl restart network
Verification
On a RHEL host in the internal workstation subnet:
Install the
traceroute
package:# yum install traceroute
Use the
traceroute
utility to display the route to a host on the internet:# traceroute redhat.com traceroute to redhat.com (209.132.183.105), 30 hops max, 60 byte packets 1 10.0.0.1 (10.0.0.1) 0.337 ms 0.260 ms 0.223 ms 2 192.0.2.1 (192.0.2.1) 0.884 ms 1.066 ms 1.248 ms ...
The output of the command displays that the router sends packets over
192.0.2.1
, which is the network of provider B.
On a RHEL host in the server subnet:
Install the
traceroute
package:# yum install traceroute
Use the
traceroute
utility to display the route to a host on the internet:# traceroute redhat.com traceroute to redhat.com (209.132.183.105), 30 hops max, 60 byte packets 1 203.0.113.1 (203.0.113.1) 2.179 ms 2.073 ms 1.944 ms 2 198.51.100.2 (198.51.100.2) 1.868 ms 1.798 ms 1.549 ms ...
The output of the command displays that the router sends packets over
198.51.100.2
, which is the network of provider A.
Troubleshooting steps
On the RHEL router:
Display the rule list:
# ip rule list 0: from all lookup local 5: from 10.0.0.0/24 lookup 5000 32766: from all lookup main 32767: from all lookup default
By default, RHEL contains rules for the tables
local
,main
, anddefault
.Display the routes in table
5000
:# ip route list table 5000 default via 192.0.2.2 dev enp1s0 10.0.0.0/24 via 192.0.2.1 dev enp1s0
Display the interfaces and firewall zones:
# firewall-cmd --get-active-zones external interfaces: enp1s0 enp7s0 internal interfaces: enp8s0 enp9s0
Verify that the
external
zone has masquerading enabled:# firewall-cmd --info-zone=external external (active) target: default icmp-block-inversion: no interfaces: enp1s0 enp7s0 sources: services: ssh ports: protocols: masquerade: yes ...
Additional resources
- Overview of configuration files involved in policy-based routing when using the legacy network scripts
-
ip-route(8)
man page -
ip-rule(8)
man page -
/usr/share/doc/network-scripts/sysconfig.txt
file
Chapter 26. Reusing the same IP address on different interfaces
With Virtual routing and forwarding (VRF), administrators can use multiple routing tables simultaneously on the same host. For that, VRF partitions a network at layer 3. This enables the administrator to isolate traffic using separate and independent route tables per VRF domain. This technique is similar to virtual LANs (VLAN), which partitions a network at layer 2, where the operating system uses different VLAN tags to isolate traffic sharing the same physical medium.
One benefit of VRF over partitioning on layer 2 is that routing scales better considering the number of peers involved.
Red Hat Enterprise Linux uses a virtual vrt
device for each VRF domain and adds routes to a VRF domain by adding existing network devices to a VRF device. Addresses and routes previously attached to the original device will be moved inside the VRF domain.
Note that each VRF domain is isolated from each other.
26.1. Permanently reusing the same IP address on different interfaces
You can use the virtual routing and forwarding (VRF) feature to permanently use the same IP address on different interfaces in one server.
To enable remote peers to contact both VRF interfaces while reusing the same IP address, the network interfaces must belong to different broadcasting domains. A broadcast domain in a network is a set of nodes, which receive broadcast traffic sent by any of them. In most configurations, all nodes connected to the same switch belong to the same broadcasting domain.
Prerequisites
-
You are logged in as the
root
user. - The network interfaces are not configured.
Procedure
Create and configure the first VRF device:
Create a connection for the VRF device and assign it to a routing table. For example, to create a VRF device named
vrf0
that is assigned to the1001
routing table:# nmcli connection add type vrf ifname vrf0 con-name vrf0 table 1001 ipv4.method disabled ipv6.method disabled
Enable the
vrf0
device:# nmcli connection up vrf0
Assign a network device to the VRF just created. For example, to add the
enp1s0
Ethernet device to thevrf0
VRF device and assign an IP address and the subnet mask toenp1s0
, enter:# nmcli connection add type ethernet con-name vrf.enp1s0 ifname enp1s0 master vrf0 ipv4.method manual ipv4.address 192.0.2.1/24
Activate the
vrf.enp1s0
connection:# nmcli connection up vrf.enp1s0
Create and configure the next VRF device:
Create the VRF device and assign it to a routing table. For example, to create a VRF device named
vrf1
that is assigned to the1002
routing table, enter:# nmcli connection add type vrf ifname vrf1 con-name vrf1 table 1002 ipv4.method disabled ipv6.method disabled
Activate the
vrf1
device:# nmcli connection up vrf1
Assign a network device to the VRF just created. For example, to add the
enp7s0
Ethernet device to thevrf1
VRF device and assign an IP address and the subnet mask toenp7s0
, enter:# nmcli connection add type ethernet con-name vrf.enp7s0 ifname enp7s0 master vrf1 ipv4.method manual ipv4.address 192.0.2.1/24
Activate the
vrf.enp7s0
device:# nmcli connection up vrf.enp7s0
26.2. Temporarily reusing the same IP address on different interfaces
You can use the virtual routing and forwarding (VRF) feature to temporarily use the same IP address on different interfaces in one server. Use this procedure only for testing purposes, because the configuration is temporary and lost after you reboot the system.
To enable remote peers to contact both VRF interfaces while reusing the same IP address, the network interfaces must belong to different broadcasting domains. A broadcast domain in a network is a set of nodes which receive broadcast traffic sent by any of them. In most configurations, all nodes connected to the same switch belong to the same broadcasting domain.
Prerequisites
-
You are logged in as the
root
user. - The network interfaces are not configured.
Procedure
Create and configure the first VRF device:
Create the VRF device and assign it to a routing table. For example, to create a VRF device named
blue
that is assigned to the1001
routing table:# ip link add dev blue type vrf table 1001
Enable the
blue
device:# ip link set dev blue up
Assign a network device to the VRF device. For example, to add the
enp1s0
Ethernet device to theblue
VRF device:# ip link set dev enp1s0 master blue
Enable the
enp1s0
device:# ip link set dev enp1s0 up
Assign an IP address and subnet mask to the
enp1s0
device. For example, to set it to192.0.2.1/24
:# ip addr add dev enp1s0 192.0.2.1/24
Create and configure the next VRF device:
Create the VRF device and assign it to a routing table. For example, to create a VRF device named
red
that is assigned to the1002
routing table:# ip link add dev red type vrf table 1002
Enable the
red
device:# ip link set dev red up
Assign a network device to the VRF device. For example, to add the
enp7s0
Ethernet device to thered
VRF device:# ip link set dev enp7s0 master red
Enable the
enp7s0
device:# ip link set dev enp7s0 up
Assign the same IP address and subnet mask to the
enp7s0
device as you used forenp1s0
in theblue
VRF domain:# ip addr add dev enp7s0 192.0.2.1/24
- Optional: Create further VRF devices as described above.
26.3. Additional resources
-
/usr/share/doc/kernel-doc-<kernel_version>/Documentation/networking/vrf.txt
from thekernel-doc
package
Chapter 27. Starting a service within an isolated VRF network
With virtual routing and forwarding (VRF), you can create isolated networks with a routing table that is different to the main routing table of the operating system. You can then start services and applications so that they have only access to the network defined in that routing table.
27.1. Configuring a VRF device
To use virtual routing and forwarding (VRF), you create a VRF device and attach a physical or virtual network interface and routing information to it.
To prevent that you lock out yourself out remotely, perform this procedure on the local console or remotely over a network interface that you do not want to assign to the VRF device.
Prerequisites
- You are logged in locally or using a network interface that is different to the one you want to assign to the VRF device.
Procedure
Create the
vrf0
connection with a same-named virtual device, and attach it to routing table1000
:# nmcli connection add type vrf ifname vrf0 con-name vrf0 table 1000 ipv4.method disabled ipv6.method disabled
Add the
enp1s0
device to thevrf0
connection, and configure the IP settings:# nmcli connection add type ethernet con-name enp1s0 ifname enp1s0 master vrf0 ipv4.method manual ipv4.address 192.0.2.1/24 ipv4.gateway 192.0.2.254
This command creates the
enp1s0
connection as a port of thevrf0
connection. Due to this configuration, the routing information are automatically assigned to the routing table1000
that is associated with thevrf0
device.If you require static routes in the isolated network:
Add the static routes:
# nmcli connection modify enp1s0 +ipv4.routes "198.51.100.0/24 192.0.2.2"
This adds a route to the
198.51.100.0/24
network that uses192.0.2.2
as the router.Activate the connection:
# nmcli connection up enp1s0
Verification
Display the IP settings of the device that is associated with
vrf0
:# ip -br addr show vrf vrf0 enp1s0 UP 192.0.2.1/24
Display the VRF devices and their associated routing table:
# ip vrf show Name Table ----------------------- vrf0 1000
Display the main routing table:
# ip route show default via 203.0.113.0/24 dev enp7s0 proto static metric 100
The main routing table does not mention any routes associated with the device
enp1s0
device or the192.0.2.1/24
subnet.Display the routing table
1000
:# ip route show table 1000 default via 192.0.2.254 dev enp1s0 proto static metric 101 broadcast 192.0.2.0 dev enp1s0 proto kernel scope link src 192.0.2.1 192.0.2.0/24 dev enp1s0 proto kernel scope link src 192.0.2.1 metric 101 local 192.0.2.1 dev enp1s0 proto kernel scope host src 192.0.2.1 broadcast 192.0.2.255 dev enp1s0 proto kernel scope link src 192.0.2.1 198.51.100.0/24 via 192.0.2.2 dev enp1s0 proto static metric 101
The
default
entry indicates that services that use this routing table, use192.0.2.254
as their default gateway and not the default gateway in the main routing table.Execute the
traceroute
utility in the network associated withvrf0
to verify that the utility uses the route from table1000
:# ip vrf exec vrf0 traceroute 203.0.113.1 traceroute to 203.0.113.1 (203.0.113.1), 30 hops max, 60 byte packets 1 192.0.2.254 (192.0.2.254) 0.516 ms 0.459 ms 0.430 ms ...
The first hop is the default gateway that is assigned to the routing table
1000
and not the default gateway from the system’s main routing table.
Additional resources
-
ip-vrf(8)
man page
27.2. Starting a service within an isolated VRF network
You can configure a service, such as the Apache HTTP Server, to start within an isolated virtual routing and forwarding (VRF) network.
Services can only bind to local IP addresses that are in the same VRF network.
Prerequisites
-
You configured the
vrf0
device. -
You configured Apache HTTP Server to listen only on the IP address that is assigned to the interface associated with the
vrf0
device.
Procedure
Display the content of the
httpd
systemd service:# systemctl cat httpd ... [Service] ExecStart=/usr/sbin/httpd $OPTIONS -DFOREGROUND ...
You require the content of the
ExecStart
parameter in a later step to run the same command within the isolated VRF network.Create the
/etc/systemd/system/httpd.service.d/
directory:# mkdir /etc/systemd/system/httpd.service.d/
Create the
/etc/systemd/system/httpd.service.d/override.conf
file with the following content:[Service] ExecStart= ExecStart=/usr/sbin/ip vrf exec vrf0 /usr/sbin/httpd $OPTIONS -DFOREGROUND
To override the
ExecStart
parameter, you first need to unset it and then set it to the new value as shown.Reload systemd.
# systemctl daemon-reload
Restart the
httpd
service.# systemctl restart httpd
Verification
Display the process IDs (PID) of
httpd
processes:# pidof -c httpd 1904 ...
Display the VRF association for the PIDs, for example:
# ip vrf identify 1904 vrf0
Display all PIDs associated with the
vrf0
device:# ip vrf pids vrf0 1904 httpd ...
Additional resources
-
ip-vrf(8)
man page
Chapter 28. Configuring ethtool settings in NetworkManager connection profiles
NetworkManager can configure certain network driver and hardware settings persistently. Compared to using the ethtool
utility to manage these settings, this has the benefit of not losing the settings after a reboot.
You can set the following ethtool
settings in NetworkManager connection profiles:
- Offload features
- Network interface controllers can use the TCP offload engine (TOE) to offload processing certain operations to the network controller. This improves the network throughput.
- Interrupt coalesce settings
- By using interrupt coalescing, the system collects network packets and generates a single interrupt for multiple packets. This increases the amount of data sent to the kernel with one hardware interrupt, which reduces the interrupt load, and maximizes the throughput.
- Ring buffers
- These buffers store incoming and outgoing network packets. You can increase the ring buffer sizes to reduce a high packet drop rate.
28.1. Configuring an ethtool offload feature by using nmcli
You can use NetworkManager to enable and disable ethtool
offload features in a connection profile.
Procedure
For example, to enable the RX offload feature and disable TX offload in the
enp1s0
connection profile, enter:# nmcli con modify enp1s0 ethtool.feature-rx on ethtool.feature-tx off
This command explicitly enables RX offload and disables TX offload.
To remove the setting of an offload feature that you previously enabled or disabled, set the feature’s parameter to a null value. For example, to remove the configuration for TX offload, enter:
# nmcli con modify enp1s0 ethtool.feature-tx ""
Reactivate the network profile:
# nmcli connection up enp1s0
Verification
Use the
ethtool -k
command to display the current offload features of a network device:# ethtool -k network_device
Additional resources
-
nm-settings-nmcli(5)
man page
28.2. Configuring an ethtool
offload feature by using the network
RHEL system role
Network interface controllers can use the TCP offload engine (TOE) to offload processing certain operations to the network controller. This improves the network throughput. You configure offload features in the connection profile of the network interface. By using Ansible and the network
RHEL system role, you can automate this process and remotely configure connection profiles on the hosts defined in a playbook.
You cannot use the network
RHEL system role to update only specific values in an existing connection profile. The role ensures that a connection profile exactly matches the settings in a playbook. If a connection profile with the same name already exists, the role applies the settings from the playbook and resets all other settings in the profile to their defaults. To prevent resetting values, always specify the whole configuration of the network connection profile in the playbook, including the settings that you do not want to change.
Prerequisites
- You have prepared the control node and the managed nodes
- You are logged in to the control node as a user who can run playbooks on the managed nodes.
-
The account you use to connect to the managed nodes has
sudo
permissions on them.
Procedure
Create a playbook file, for example
~/playbook.yml
, with the following content:--- - name: Configure the network hosts: managed-node-01.example.com tasks: - name: Ethernet connection profile with dynamic IP address settings and offload features ansible.builtin.include_role: name: rhel-system-roles.network vars: network_connections: - name: enp1s0 type: ethernet autoconnect: yes ip: dhcp4: yes auto6: yes ethtool: features: gro: no gso: yes tx_sctp_segmentation: no state: up
The settings specified in the example playbook include the following:
gro: no
- Disables Generic receive offload (GRO).
gso: yes
- Enables Generic segmentation offload (GSO).
tx_sctp_segmentation: no
- Disables TX stream control transmission protocol (SCTP) segmentation.
For details about all variables used in the playbook, see the
/usr/share/ansible/roles/rhel-system-roles.network/README.md
file on the control node.Validate the playbook syntax:
$ ansible-playbook --syntax-check ~/playbook.yml
Note that this command only validates the syntax and does not protect against a wrong but valid configuration.
Run the playbook:
$ ansible-playbook ~/playbook.yml
Verification
Query the Ansible facts of the managed node and verify the offload settings:
# ansible managed-node-01.example.com -m ansible.builtin.setup ... "ansible_enp1s0": { "active": true, "device": "enp1s0", "features": { ... "rx_gro_hw": "off, ... "tx_gso_list": "on, ... "tx_sctp_segmentation": "off", ... } ...
Additional resources
-
/usr/share/ansible/roles/rhel-system-roles.network/README.md
file -
/usr/share/doc/rhel-system-roles/network/
directory
28.3. Configuring an ethtool coalesce settings by using nmcli
You can use NetworkManager to set ethtool
coalesce settings in connection profiles.
Procedure
For example, to set the maximum number of received packets to delay to
128
in theenp1s0
connection profile, enter:# nmcli connection modify enp1s0 ethtool.coalesce-rx-frames 128
To remove a coalesce setting, set it to a null value. For example, to remove the
ethtool.coalesce-rx-frames
setting, enter:# nmcli connection modify enp1s0 ethtool.coalesce-rx-frames ""
To reactivate the network profile:
# nmcli connection up enp1s0
Verification
Use the
ethtool -c
command to display the current offload features of a network device:# ethtool -c network_device
Additional resources
-
nm-settings-nmcli(5)
man page
28.4. Configuring an ethtool
coalesce settings by using the network
RHEL system role
By using interrupt coalescing, the system collects network packets and generates a single interrupt for multiple packets. This increases the amount of data sent to the kernel with one hardware interrupt, which reduces the interrupt load, and maximizes the throughput. You configure coalesce settings in the connection profile of the network interface. By using Ansible and the network
RHEL role, you can automate this process and remotely configure connection profiles on the hosts defined in a playbook.
You cannot use the network
RHEL system role to update only specific values in an existing connection profile. The role ensures that a connection profile exactly matches the settings in a playbook. If a connection profile with the same name already exists, the role applies the settings from the playbook and resets all other settings in the profile to their defaults. To prevent resetting values, always specify the whole configuration of the network connection profile in the playbook, including the settings that you do not want to change.
Prerequisites
- You have prepared the control node and the managed nodes
- You are logged in to the control node as a user who can run playbooks on the managed nodes.
-
The account you use to connect to the managed nodes has
sudo
permissions on them.
Procedure
Create a playbook file, for example
~/playbook.yml
, with the following content:--- - name: Configure the network hosts: managed-node-01.example.com tasks: - name: Ethernet connection profile with dynamic IP address settings and coalesce settings ansible.builtin.include_role: name: rhel-system-roles.network vars: network_connections: - name: enp1s0 type: ethernet autoconnect: yes ip: dhcp4: yes auto6: yes ethtool: coalesce: rx_frames: 128 tx_frames: 128 state: up
The settings specified in the example playbook include the following:
rx_frames: <value>
- Sets the number of RX frames.
gso: <value>
- Sets the number of TX frames.
For details about all variables used in the playbook, see the
/usr/share/ansible/roles/rhel-system-roles.network/README.md
file on the control node.Validate the playbook syntax:
$ ansible-playbook --syntax-check ~/playbook.yml
Note that this command only validates the syntax and does not protect against a wrong but valid configuration.
Run the playbook:
$ ansible-playbook ~/playbook.yml
Verification
Display the current offload features of the network device:
# ansible managed-node-01.example.com -m command -a 'ethtool -c enp1s0' managed-node-01.example.com | CHANGED | rc=0 >> ... rx-frames: 128 ... tx-frames: 128 ...
Additional resources
-
/usr/share/ansible/roles/rhel-system-roles.network/README.md
file -
/usr/share/doc/rhel-system-roles/network/
directory
28.5. Increasing the ring buffer size to reduce a high packet drop rate by using nmcli
Increase the size of an Ethernet device’s ring buffers if the packet drop rate causes applications to report a loss of data, timeouts, or other issues.
Receive ring buffers are shared between the device driver and network interface controller (NIC). The card assigns a transmit (TX) and receive (RX) ring buffer. As the name implies, the ring buffer is a circular buffer where an overflow overwrites existing data. There are two ways to move data from the NIC to the kernel, hardware interrupts and software interrupts, also called SoftIRQs.
The kernel uses the RX ring buffer to store incoming packets until the device driver can process them. The device driver drains the RX ring, typically by using SoftIRQs, which puts the incoming packets into a kernel data structure called an sk_buff
or skb
to begin its journey through the kernel and up to the application that owns the relevant socket.
The kernel uses the TX ring buffer to hold outgoing packets which should be sent to the network. These ring buffers reside at the bottom of the stack and are a crucial point at which packet drop can occur, which in turn will adversely affect network performance.
Procedure
Display the packet drop statistics of the interface:
# ethtool -S enp1s0 ... rx_queue_0_drops: 97326 rx_queue_1_drops: 63783 ...
Note that the output of the command depends on the network card and the driver.
High values in
discard
ordrop
counters indicate that the available buffer fills up faster than the kernel can process the packets. Increasing the ring buffers can help to avoid such loss.Display the maximum ring buffer sizes:
# ethtool -g enp1s0 Ring parameters for enp1s0: Pre-set maximums: RX: 4096 RX Mini: 0 RX Jumbo: 16320 TX: 4096 Current hardware settings: RX: 255 RX Mini: 0 RX Jumbo: 0 TX: 255
If the values in the
Pre-set maximums
section are higher than in theCurrent hardware settings
section, you can change the settings in the next steps.Identify the NetworkManager connection profile that uses the interface:
# nmcli connection show NAME UUID TYPE DEVICE Example-Connection a5eb6490-cc20-3668-81f8-0314a27f3f75 ethernet enp1s0
Update the connection profile, and increase the ring buffers:
To increase the RX ring buffer, enter:
# nmcli connection modify Example-Connection ethtool.ring-rx 4096
To increase the TX ring buffer, enter:
# nmcli connection modify Example-Connection ethtool.ring-tx 4096
Reload the NetworkManager connection:
# nmcli connection up Example-Connection
ImportantDepending on the driver your NIC uses, changing in the ring buffer can shortly interrupt the network connection.
Additional resources
28.6. Increasing the ring buffer size to reduce a high packet drop rate by using the network
RHEL system role
Increase the size of an Ethernet device’s ring buffers if the packet drop rate causes applications to report a loss of data, timeouts, or other issues.
Ring buffers are circular buffers where an overflow overwrites existing data. The network card assigns a transmit (TX) and receive (RX) ring buffer. Receive ring buffers are shared between the device driver and the network interface controller (NIC). Data can move from NIC to the kernel through either hardware interrupts or software interrupts, also called SoftIRQs.
The kernel uses the RX ring buffer to store incoming packets until the device driver can process them. The device driver drains the RX ring, typically by using SoftIRQs, which puts the incoming packets into a kernel data structure called an sk_buff
or skb
to begin its journey through the kernel and up to the application that owns the relevant socket.
The kernel uses the TX ring buffer to hold outgoing packets which should be sent to the network. These ring buffers reside at the bottom of the stack and are a crucial point at which packet drop can occur, which in turn will adversely affect network performance.
You configure ring buffer settings in the NetworkManager connection profiles. By using Ansible and the network
RHEL system role, you can automate this process and remotely configure connection profiles on the hosts defined in a playbook.
You cannot use the network
RHEL system role to update only specific values in an existing connection profile. The role ensures that a connection profile exactly matches the settings in a playbook. If a connection profile with the same name already exists, the role applies the settings from the playbook and resets all other settings in the profile to their defaults. To prevent resetting values, always specify the whole configuration of the network connection profile in the playbook, including the settings that you do not want to change.
Prerequisites
- You have prepared the control node and the managed nodes
- You are logged in to the control node as a user who can run playbooks on the managed nodes.
-
The account you use to connect to the managed nodes has
sudo
permissions on them. - You know the maximum ring buffer sizes that the device supports.
Procedure
Create a playbook file, for example
~/playbook.yml
, with the following content:--- - name: Configure the network hosts: managed-node-01.example.com tasks: - name: Ethernet connection profile with dynamic IP address setting and increased ring buffer sizes ansible.builtin.include_role: name: rhel-system-roles.network vars: network_connections: - name: enp1s0 type: ethernet autoconnect: yes ip: dhcp4: yes auto6: yes ethtool: ring: rx: 4096 tx: 4096 state: up
The settings specified in the example playbook include the following:
rx: <value>
- Sets the maximum number of received ring buffer entries.
tx: <value>
- Sets the maximum number of transmitted ring buffer entries.
For details about all variables used in the playbook, see the
/usr/share/ansible/roles/rhel-system-roles.network/README.md
file on the control node.Validate the playbook syntax:
$ ansible-playbook --syntax-check ~/playbook.yml
Note that this command only validates the syntax and does not protect against a wrong but valid configuration.
Run the playbook:
$ ansible-playbook ~/playbook.yml
Verification
Display the maximum ring buffer sizes:
# ansible managed-node-01.example.com -m command -a 'ethtool -g enp1s0' managed-node-01.example.com | CHANGED | rc=0 >> ... Current hardware settings: RX: 4096 RX Mini: 0 RX Jumbo: 0 TX: 4096
Additional resources
-
/usr/share/ansible/roles/rhel-system-roles.network/README.md
file -
/usr/share/doc/rhel-system-roles/network/
directory
Chapter 29. Introduction to NetworkManager Debugging
Increasing the log levels for all or certain domains helps to log more details of the operations that NetworkManager performs. You can use this information to troubleshoot problems. NetworkManager provides different levels and domains to produce logging information. The /etc/NetworkManager/NetworkManager.conf
file is the main configuration file for NetworkManager. The logs are stored in the journal.
29.1. Introduction to NetworkManager reapply method
The NetworkManager
service uses a profile to manage the connection settings of a device. Desktop Bus (D-Bus) API can create, modify, and delete these connection settings. For any changes in a profile, D-Bus API clones the existing settings to the modified settings of a connection. Despite cloning, changes do not apply to the modified settings. To make it effective, reactivate the existing settings of a connection or use the reapply()
method.
The reapply()
method has the following features:
- Updating modified connection settings without deactivation or restart of a network interface.
-
Removing pending changes from the modified connection settings. As
NetworkManager
does not revert the manual changes, you can reconfigure the device and revert external or manual parameters. - Creating different modified connection settings than that of the existing connection settings.
Also, reapply()
method supports the following attributes:
-
bridge.ageing-time
-
bridge.forward-delay
-
bridge.group-address
-
bridge.group-forward-mask
-
bridge.hello-time
-
bridge.max-age
-
bridge.multicast-hash-max
-
bridge.multicast-last-member-count
-
bridge.multicast-last-member-interval
-
bridge.multicast-membership-interval
-
bridge.multicast-querier
-
bridge.multicast-querier-interval
-
bridge.multicast-query-interval
-
bridge.multicast-query-response-interval
-
bridge.multicast-query-use-ifaddr
-
bridge.multicast-router
-
bridge.multicast-snooping
-
bridge.multicast-startup-query-count
-
bridge.multicast-startup-query-interval
-
bridge.priority
-
bridge.stp
-
bridge.VLAN-filtering
-
bridge.VLAN-protocol
-
bridge.VLANs
-
802-3-ethernet.accept-all-mac-addresses
-
802-3-ethernet.cloned-mac-address
-
IPv4.addresses
-
IPv4.dhcp-client-id
-
IPv4.dhcp-iaid
-
IPv4.dhcp-timeout
-
IPv4.DNS
-
IPv4.DNS-priority
-
IPv4.DNS-search
-
IPv4.gateway
-
IPv4.ignore-auto-DNS
-
IPv4.ignore-auto-routes
-
IPv4.may-fail
-
IPv4.method
-
IPv4.never-default
-
IPv4.route-table
-
IPv4.routes
-
IPv4.routing-rules
-
IPv6.addr-gen-mode
-
IPv6.addresses
-
IPv6.dhcp-duid
-
IPv6.dhcp-iaid
-
IPv6.dhcp-timeout
-
IPv6.DNS
-
IPv6.DNS-priority
-
IPv6.DNS-search
-
IPv6.gateway
-
IPv6.ignore-auto-DNS
-
IPv6.may-fail
-
IPv6.method
-
IPv6.never-default
-
IPv6.ra-timeout
-
IPv6.route-metric
-
IPv6.route-table
-
IPv6.routes
-
IPv6.routing-rules
Additional resources
-
nm-settings-nmcli(5)
man page
29.2. Setting the NetworkManager log level
By default, all the log domains are set to record the INFO
log level. Disable rate-limiting before collecting debug logs. With rate-limiting, systemd-journald
drops messages if there are too many of them in a short time. This can occur when the log level is TRACE
.
This procedure disables rate-limiting and enables recording debug logs for the all (ALL) domains.
Procedure
To disable rate-limiting, edit the
/etc/systemd/journald.conf
file, uncomment theRateLimitBurst
parameter in the[Journal]
section, and set its value as0
:RateLimitBurst=0
Restart the
systemd-journald
service.# systemctl restart systemd-journald
Create the
/etc/NetworkManager/conf.d/95-nm-debug.conf
file with the following content:[logging] domains=ALL:TRACE
The
domains
parameter can contain multiple comma-separateddomain:level
pairs.Restart the NetworkManager service.
# systemctl restart NetworkManager
Verification
Query the
systemd
journal to display the journal entries of theNetworkManager
unit:# journalctl -u NetworkManager ... Jun 30 15:24:32 server NetworkManager[164187]: <debug> [1656595472.4939] active-connection[0x5565143c80a0]: update activation type from assume to managed Jun 30 15:24:32 server NetworkManager[164187]: <trace> [1656595472.4939] device[55b33c3bdb72840c] (enp1s0): sys-iface-state: assume -> managed Jun 30 15:24:32 server NetworkManager[164187]: <trace> [1656595472.4939] l3cfg[4281fdf43e356454,ifindex=3]: commit type register (type "update", source "device", existing a369f23014b9ede3) -> a369f23014b9ede3 Jun 30 15:24:32 server NetworkManager[164187]: <info> [1656595472.4940] manager: NetworkManager state is now CONNECTED_SITE ...
29.3. Temporarily setting log levels at run time using nmcli
You can change the log level at run time using nmcli
.
Procedure
Optional: Display the current logging settings:
# nmcli general logging LEVEL DOMAINS INFO PLATFORM,RFKILL,ETHER,WIFI,BT,MB,DHCP4,DHCP6,PPP,WIFI_SCAN,IP4,IP6,A UTOIP4,DNS,VPN,SHARING,SUPPLICANT,AGENTS,SETTINGS,SUSPEND,CORE,DEVICE,OLPC, WIMAX,INFINIBAND,FIREWALL,ADSL,BOND,VLAN,BRIDGE,DBUS_PROPS,TEAM,CONCHECK,DC B,DISPATCH
To modify the logging level and domains, use the following options:
To set the log level for all domains to the same
LEVEL
, enter:# nmcli general logging level LEVEL domains ALL
To change the level for specific domains, enter:
# nmcli general logging level LEVEL domains DOMAINS
Note that updating the logging level using this command disables logging for all the other domains.
To change the level of specific domains and preserve the level of all other domains, enter:
# nmcli general logging level KEEP domains DOMAIN:LEVEL,DOMAIN:LEVEL
29.4. Viewing NetworkManager logs
You can view the NetworkManager logs for troubleshooting.
Procedure
To view the logs, enter:
# journalctl -u NetworkManager -b
Additional resources
-
NetworkManager.conf(5)
man page -
journalctl(1)
man page
29.5. Debugging levels and domains
You can use the levels
and domains
parameters to manage the debugging for NetworkManager. The level defines the verbosity level, whereas the domains define the category of the messages to record the logs with given severity (level
).
Log levels | Description |
---|---|
| Does not log any messages about NetworkManager |
| Logs only critical errors |
| Logs warnings that can reflect the operation |
| Logs various informational messages that are useful for tracking state and operations |
| Enables verbose logging for debugging purposes |
|
Enables more verbose logging than the |
Note that subsequent levels log all messages from earlier levels. For example, setting the log level to INFO
also logs messages contained in the ERR
and WARN
log level.
Additional resources
-
NetworkManager.conf(5)
man page
Chapter 30. Using LLDP to debug network configuration problems
You can use the Link Layer Discovery Protocol (LLDP) to debug network configuration problems in the topology. This means that, LLDP can report configuration inconsistencies with other hosts or routers and switches.
30.1. Debugging an incorrect VLAN configuration using LLDP information
If you configured a switch port to use a certain VLAN and a host does not receive these VLAN packets, you can use the Link Layer Discovery Protocol (LLDP) to debug the problem. Perform this procedure on the host that does not receive the packets.
Prerequisites
-
The
nmstate
package is installed. - The switch supports LLDP.
- LLDP is enabled on neighbor devices.
Procedure
Create the
~/enable-LLDP-enp1s0.yml
file with the following content:interfaces: - name: enp1s0 type: ethernet lldp: enabled: true
Use the
~/enable-LLDP-enp1s0.yml
file to enable LLDP on interfaceenp1s0
:# nmstatectl apply ~/enable-LLDP-enp1s0.yml
Display the LLDP information:
# nmstatectl show enp1s0 - name: enp1s0 type: ethernet state: up ipv4: enabled: false dhcp: false ipv6: enabled: false autoconf: false dhcp: false lldp: enabled: true neighbors: - - type: 5 system-name: Summit300-48 - type: 6 system-description: Summit300-48 - Version 7.4e.1 (Build 5) 05/27/05 04:53:11 - type: 7 system-capabilities: - MAC Bridge component - Router - type: 1 _description: MAC address chassis-id: 00:01:30:F9:AD:A0 chassis-id-type: 4 - type: 2 _description: Interface name port-id: 1/1 port-id-type: 5 - type: 127 ieee-802-1-vlans: - name: v2-0488-03-0505 vid: 488 oui: 00:80:c2 subtype: 3 - type: 127 ieee-802-3-mac-phy-conf: autoneg: true operational-mau-type: 16 pmd-autoneg-cap: 27648 oui: 00:12:0f subtype: 1 - type: 127 ieee-802-1-ppvids: - 0 oui: 00:80:c2 subtype: 2 - type: 8 management-addresses: - address: 00:01:30:F9:AD:A0 address-subtype: MAC interface-number: 1001 interface-number-subtype: 2 - type: 127 ieee-802-3-max-frame-size: 1522 oui: 00:12:0f subtype: 4 mac-address: 82:75:BE:6F:8C:7A mtu: 1500
Verify the output to ensure that the settings match your expected configuration. For example, the LLDP information of the interface connected to the switch shows that the switch port this host is connected to uses VLAN ID
448
:- type: 127 ieee-802-1-vlans: - name: v2-0488-03-0505 vid: 488
If the network configuration of the
enp1s0
interface uses a different VLAN ID, change it accordingly.
Additional resources
Chapter 31. Linux traffic control
Linux offers tools for managing and manipulating the transmission of packets. The Linux Traffic Control (TC) subsystem helps in policing, classifying, shaping, and scheduling network traffic. TC also mangles the packet content during classification by using filters and actions. The TC subsystem achieves this by using queuing disciplines (qdisc
), a fundamental element of the TC architecture.
The scheduling mechanism arranges or rearranges the packets before they enter or exit different queues. The most common scheduler is the First-In-First-Out (FIFO) scheduler. You can do the qdiscs
operations temporarily using the tc
utility or permanently using NetworkManager.
In Red Hat Enterprise Linux, you can configure default queueing disciplines in various ways to manage the traffic on a network interface.
31.1. Overview of queuing disciplines
Queuing disciplines (qdiscs
) help with queuing up and, later, scheduling of traffic transmission by a network interface. A qdisc
has two operations;
- enqueue requests so that a packet can be queued up for later transmission and
- dequeue requests so that one of the queued-up packets can be chosen for immediate transmission.
Every qdisc
has a 16-bit hexadecimal identification number called a handle
, with an attached colon, such as 1:
or abcd:
. This number is called the qdisc
major number. If a qdisc
has classes, then the identifiers are formed as a pair of two numbers with the major number before the minor, <major>:<minor>
, for example abcd:1
. The numbering scheme for the minor numbers depends on the qdisc
type. Sometimes the numbering is systematic, where the first-class has the ID <major>:1
, the second one <major>:2
, and so on. Some qdiscs
allow the user to set class minor numbers arbitrarily when creating the class.
- Classful
qdiscs
Different types of
qdiscs
exist and help in the transfer of packets to and from a networking interface. You can configureqdiscs
with root, parent, or child classes. The point where children can be attached are called classes. Classes inqdisc
are flexible and can always contain either multiple children classes or a single child,qdisc
. There is no prohibition against a class containing a classfulqdisc
itself, this facilitates complex traffic control scenarios.Classful
qdiscs
do not store any packets themselves. Instead, they enqueue and dequeue requests down to one of their children according to criteria specific to theqdisc
. Eventually, this recursive packet passing ends up where the packets are stored (or picked up from in the case of dequeuing).- Classless
qdiscs
-
Some
qdiscs
contain no child classes and they are called classlessqdiscs
. Classlessqdiscs
require less customization compared to classfulqdiscs
. It is usually enough to attach them to an interface.
Additional resources
-
tc(8)
man page -
tc-actions(8)
man page
31.2. Inspecting qdiscs of a network interface using the tc utility
By default, Red Hat Enterprise Linux systems use fq_codel
qdisc
. You can inspect the qdisc
counters using the tc
utility.
Procedure
Optional: View your current
qdisc
:# tc qdisc show dev enp0s1
Inspect the current
qdisc
counters:# tc -s qdisc show dev enp0s1 qdisc fq_codel 0: root refcnt 2 limit 10240p flows 1024 quantum 1514 target 5.0ms interval 100.0ms memory_limit 32Mb ecn Sent 1008193 bytes 5559 pkt (dropped 233, overlimits 55 requeues 77) backlog 0b 0p requeues 0
-
dropped
- the number of times a packet is dropped because all queues are full -
overlimits
- the number of times the configured link capacity is filled -
sent
- the number of dequeues
-
31.3. Updating the default qdisc
If you observe networking packet losses with the current qdisc
, you can change the qdisc
based on your network-requirements.
Procedure
View the current default
qdisc
:# sysctl -a | grep qdisc net.core.default_qdisc = fq_codel
View the
qdisc
of current Ethernet connection:# tc -s qdisc show dev enp0s1 qdisc fq_codel 0: root refcnt 2 limit 10240p flows 1024 quantum 1514 target 5.0ms interval 100.0ms memory_limit 32Mb ecn Sent 0 bytes 0 pkt (dropped 0, overlimits 0 requeues 0) backlog 0b 0p requeues 0 maxpacket 0 drop_overlimit 0 new_flow_count 0 ecn_mark 0 new_flows_len 0 old_flows_len 0
Update the existing
qdisc
:# sysctl -w net.core.default_qdisc=pfifo_fast
To apply the changes, reload the network driver:
# modprobe -r NETWORKDRIVERNAME # modprobe NETWORKDRIVERNAME
Start the network interface:
# ip link set enp0s1 up
Verification
View the
qdisc
of the Ethernet connection:# tc -s qdisc show dev enp0s1 qdisc pfifo_fast 0: root refcnt 2 bands 3 priomap 1 2 2 2 1 2 0 0 1 1 1 1 1 1 1 1 Sent 373186 bytes 5333 pkt (dropped 0, overlimits 0 requeues 0) backlog 0b 0p requeues 0 ....
Additional resources
31.4. Temporarily setting the current qdisc of a network interface using the tc utility
You can update the current qdisc
without changing the default one.
Procedure
Optional: View the current
qdisc
:# tc -s qdisc show dev enp0s1
Update the current
qdisc
:# tc qdisc replace dev enp0s1 root htb
Verification
View the updated current
qdisc
:# tc -s qdisc show dev enp0s1 qdisc htb 8001: root refcnt 2 r2q 10 default 0 direct_packets_stat 0 direct_qlen 1000 Sent 0 bytes 0 pkt (dropped 0, overlimits 0 requeues 0) backlog 0b 0p requeues 0
31.5. Permanently setting the current qdisc of a network interface using NetworkManager
You can update the current qdisc
value of a NetworkManager connection.
Procedure
Optional: View the current
qdisc
:# tc qdisc show dev enp0s1 qdisc fq_codel 0: root refcnt 2
Update the current
qdisc
:# nmcli connection modify enp0s1 tc.qdiscs 'root pfifo_fast'
Optional: To add another
qdisc
over the existingqdisc
, use the+tc.qdisc
option:# nmcli connection modify enp0s1 +tc.qdisc 'ingress handle ffff:'
Activate the changes:
# nmcli connection up enp0s1
Verification
View current
qdisc
the network interface:# tc qdisc show dev enp0s1 qdisc pfifo_fast 8001: root refcnt 2 bands 3 priomap 1 2 2 2 1 2 0 0 1 1 1 1 1 1 1 1 qdisc ingress ffff: parent ffff:fff1 ----------------
Additional resources
-
nm-settings(5)
man page
31.6. Available qdiscs in RHEL
Each qdisc
addresses unique networking-related issues. The following is the list of qdiscs
available in RHEL. You can use any of the following qdisc
to shape network traffic based on your networking requirements.
qdisc name | Included in | Offload support |
---|---|---|
Asynchronous Transfer Mode (ATM) |
| |
Class-Based Queueing |
| |
Credit-Based Shaper |
| Yes |
CHOose and Keep for responsive flows, CHOose and Kill for unresponsive flows (CHOKE) |
| |
Controlled Delay (CoDel) |
| |
Deficit Round Robin (DRR) |
| |
Differentiated Services marker (DSMARK) |
| |
Enhanced Transmission Selection (ETS) |
| Yes |
Fair Queue (FQ) |
| |
Fair Queuing Controlled Delay (FQ_CODel) |
| |
Generalized Random Early Detection (GRED) |
| |
Hierarchical Fair Service Curve (HSFC) |
| |
Heavy-Hitter Filter (HHF) |
| |
Hierarchy Token Bucket (HTB) |
| |
INGRESS |
| Yes |
Multi Queue Priority (MQPRIO) |
| Yes |
Multiqueue (MULTIQ) |
| Yes |
Network Emulator (NETEM) |
| |
Proportional Integral-controller Enhanced (PIE) |
| |
PLUG |
| |
Quick Fair Queueing (QFQ) |
| |
Random Early Detection (RED) |
| Yes |
Stochastic Fair Blue (SFB) |
| |
Stochastic Fairness Queueing (SFQ) |
| |
Token Bucket Filter (TBF) |
| Yes |
Trivial Link Equalizer (TEQL) |
|
The qdisc
offload requires hardware and driver support on NIC.
Additional resources
-
tc(8)
man page
Chapter 32. Authenticating a RHEL client to the network by using the 802.1X standard with a certificate stored on the file system
Administrators frequently use port-based Network Access Control (NAC) based on the IEEE 802.1X standard to protect a network from unauthorized LAN and Wi-Fi clients. To enable a client to connect to such networks, you must configure 802.1X authentication on this clients.
32.1. Configuring 802.1X network authentication on an existing Ethernet connection by using nmcli
You can use the nmcli
utility to configure an Ethernet connection with 802.1X network authentication on the command line.
Prerequisites
- The network supports 802.1X network authentication.
- The Ethernet connection profile exists in NetworkManager and has a valid IP configuration.
The following files required for TLS authentication exist on the client:
-
The client key stored is in the
/etc/pki/tls/private/client.key
file, and the file is owned and only readable by theroot
user. -
The client certificate is stored in the
/etc/pki/tls/certs/client.crt
file. -
The Certificate Authority (CA) certificate is stored in the
/etc/pki/tls/certs/ca.crt
file.
-
The client key stored is in the
-
The
wpa_supplicant
package is installed.
Procedure
Set the Extensible Authentication Protocol (EAP) to
tls
and the paths to the client certificate and key file:# nmcli connection modify enp1s0 802-1x.eap tls 802-1x.client-cert /etc/pki/tls/certs/client.crt 802-1x.private-key /etc/pki/tls/certs/certs/client.key
Note that you must set the
802-1x.eap
,802-1x.client-cert
, and802-1x.private-key
parameters in a single command.Set the path to the CA certificate:
# nmcli connection modify enp1s0 802-1x.ca-cert /etc/pki/tls/certs/ca.crt
Set the identity of the user used in the certificate:
# nmcli connection modify enp1s0 802-1x.identity user@example.com
Optional: Store the password in the configuration:
# nmcli connection modify enp1s0 802-1x.private-key-password password
ImportantBy default, NetworkManager stores the password in clear text in the connection profile on the disk, but the file is readable only by the
root
user. However, clear text passwords in a configuration file can be a security risk.To increase the security, set the
802-1x.password-flags
parameter to0x1
. With this setting, on servers with the GNOME desktop environment or thenm-applet
running, NetworkManager retrieves the password from these services. In other cases, NetworkManager prompts for the password.Activate the connection profile:
# nmcli connection up enp1s0
Verification
- Access resources on the network that require network authentication.
Additional resources
32.2. Configuring a static Ethernet connection with 802.1X network authentication by using nmstatectl
Use the nmstatectl
utility to configure an Ethernet connection with 802.1X network authentication through the Nmstate API. The Nmstate API ensures that, after setting the configuration, the result matches the configuration file. If anything fails, nmstatectl
automatically rolls back the changes to avoid leaving the system in an incorrect state.
The nmstate
library only supports the TLS
Extensible Authentication Protocol (EAP) method.
Prerequisites
- The network supports 802.1X network authentication.
- The managed node uses NetworkManager.
The following files required for TLS authentication exist on the client:
-
The client key stored is in the
/etc/pki/tls/private/client.key
file, and the file is owned and only readable by theroot
user. -
The client certificate is stored in the
/etc/pki/tls/certs/client.crt
file. -
The Certificate Authority (CA) certificate is stored in the
/etc/pki/tls/certs/ca.crt
file.
-
The client key stored is in the
Procedure
Create a YAML file, for example
~/create-ethernet-profile.yml
, with the following content:--- interfaces: - name: enp1s0 type: ethernet state: up ipv4: enabled: true address: - ip: 192.0.2.1 prefix-length: 24 dhcp: false ipv6: enabled: true address: - ip: 2001:db8:1::1 prefix-length: 64 autoconf: false dhcp: false 802.1x: ca-cert: /etc/pki/tls/certs/ca.crt client-cert: /etc/pki/tls/certs/client.crt eap-methods: - tls identity: client.example.org private-key: /etc/pki/tls/private/client.key private-key-password: password routes: config: - destination: 0.0.0.0/0 next-hop-address: 192.0.2.254 next-hop-interface: enp1s0 - destination: ::/0 next-hop-address: 2001:db8:1::fffe next-hop-interface: enp1s0 dns-resolver: config: search: - example.com server: - 192.0.2.200 - 2001:db8:1::ffbb
These settings define an Ethernet connection profile for the
enp1s0
device with the following settings:-
A static IPv4 address -
192.0.2.1
with a/24
subnet mask -
A static IPv6 address -
2001:db8:1::1
with a/64
subnet mask -
An IPv4 default gateway -
192.0.2.254
-
An IPv6 default gateway -
2001:db8:1::fffe
-
An IPv4 DNS server -
192.0.2.200
-
An IPv6 DNS server -
2001:db8:1::ffbb
-
A DNS search domain -
example.com
-
802.1X network authentication using the
TLS
EAP protocol
-
A static IPv4 address -
Apply the settings to the system:
# nmstatectl apply ~/create-ethernet-profile.yml
Verification
- Access resources on the network that require network authentication.
32.3. Configuring a static Ethernet connection with 802.1X network authentication by using the network
RHEL system role
Network Access Control (NAC) protects a network from unauthorized clients. You can specify the details that are required for the authentication in NetworkManager connection profiles to enable clients to access the network. By using Ansible and the network
RHEL system role, you can automate this process and remotely configure connection profiles on the hosts defined in a playbook.
You can use an Ansible playbook to copy a private key, a certificate, and the CA certificate to the client, and then use the network
RHEL system role to configure a connection profile with 802.1X network authentication.
Prerequisites
- You have prepared the control node and the managed nodes
- You are logged in to the control node as a user who can run playbooks on the managed nodes.
-
The account you use to connect to the managed nodes has
sudo
permissions on them. - The network supports 802.1X network authentication.
- The managed nodes use NetworkManager.
The following files required for the TLS authentication exist on the control node:
-
The client key is stored in the
/srv/data/client.key
file. -
The client certificate is stored in the
/srv/data/client.crt
file. -
The Certificate Authority (CA) certificate is stored in the
/srv/data/ca.crt
file.
-
The client key is stored in the
Procedure
Store your sensitive variables in an encrypted file:
Create the vault:
$ ansible-vault create vault.yml New Vault password: <vault_password> Confirm New Vault password: <vault_password>
After the
ansible-vault create
command opens an editor, enter the sensitive data in the<key>: <value>
format:pwd: <password>
- Save the changes, and close the editor. Ansible encrypts the data in the vault.
Create a playbook file, for example
~/playbook.yml
, with the following content:--- - name: Configure an Ethernet connection with 802.1X authentication hosts: managed-node-01.example.com vars_files: - vault.yml tasks: - name: Copy client key for 802.1X authentication ansible.builtin.copy: src: "/srv/data/client.key" dest: "/etc/pki/tls/private/client.key" mode: 0600 - name: Copy client certificate for 802.1X authentication ansible.builtin.copy: src: "/srv/data/client.crt" dest: "/etc/pki/tls/certs/client.crt" - name: Copy CA certificate for 802.1X authentication ansible.builtin.copy: src: "/srv/data/ca.crt" dest: "/etc/pki/ca-trust/source/anchors/ca.crt" - name: Ethernet connection profile with static IP address settings and 802.1X ansible.builtin.include_role: name: rhel-system-roles.network vars: network_connections: - name: enp1s0 type: ethernet autoconnect: yes ip: address: - 192.0.2.1/24 - 2001:db8:1::1/64 gateway4: 192.0.2.254 gateway6: 2001:db8:1::fffe dns: - 192.0.2.200 - 2001:db8:1::ffbb dns_search: - example.com ieee802_1x: identity: <user_name> eap: tls private_key: "/etc/pki/tls/private/client.key" private_key_password: "{{ pwd }}" client_cert: "/etc/pki/tls/certs/client.crt" ca_cert: "/etc/pki/ca-trust/source/anchors/ca.crt" domain_suffix_match: example.com state: up
The settings specified in the example playbook include the following:
ieee802_1x
- This variable contains the 802.1X-related settings.
eap: tls
-
Configures the profile to use the certificate-based
TLS
authentication method for the Extensible Authentication Protocol (EAP).
For details about all variables used in the playbook, see the
/usr/share/ansible/roles/rhel-system-roles.network/README.md
file on the control node.Validate the playbook syntax:
$ ansible-playbook --ask-vault-pass --syntax-check ~/playbook.yml
Note that this command only validates the syntax and does not protect against a wrong but valid configuration.
Run the playbook:
$ ansible-playbook --ask-vault-pass ~/playbook.yml
Verification
- Access resources on the network that require network authentication.
Additional resources
-
/usr/share/ansible/roles/rhel-system-roles.network/README.md
file -
/usr/share/doc/rhel-system-roles/network/
directory - Ansible vault
Chapter 33. Setting up an 802.1x network authentication service for LAN clients by using hostapd
with FreeRADIUS backend
The IEEE 802.1X standard defines secure authentication and authorization methods to protect networks from unauthorized clients. By using the hostapd
service and FreeRADIUS, you can provide network access control (NAC) in your network.
In this documentation, the RHEL host acts as a bridge to connect different clients with an existing network. However, the RHEL host grants only authenticated clients access to the network.
![rhel authenticator 802 1x](https://access.redhat.com/webassets/avalon/d/Red_Hat_Enterprise_Linux-8-Configuring_and_managing_networking-en-US/images/8fadf9abfcbb769d775871aa6a9b2e22/rhel-authenticator-802-1x.png)
33.1. Prerequisites
A clean installation of the
freeradius
package.If the package is already installed, remove the
/etc/raddb/
directory, uninstall and then install the package again. Do not reinstall the package by using theyum reinstall
command, because the permissions and symbolic links in the/etc/raddb/
directory are then different.
33.2. Setting up the bridge on the authenticator
A network bridge is a link-layer device which forwards traffic between hosts and networks based on a table of MAC addresses. If you set up RHEL as an 802.1X authenticator, add both the interfaces on which to perform authentication and the LAN interface to the bridge.
Prerequisites
- The server has multiple Ethernet interfaces.
Procedure
Create the bridge interface:
# nmcli connection add type bridge con-name br0 ifname br0
Assign the Ethernet interfaces to the bridge:
# nmcli connection add type ethernet slave-type bridge con-name br0-port1 ifname enp1s0 master br0 # nmcli connection add type ethernet slave-type bridge con-name br0-port2 ifname enp7s0 master br0 # nmcli connection add type ethernet slave-type bridge con-name br0-port3 ifname enp8s0 master br0 # nmcli connection add type ethernet slave-type bridge con-name br0-port4 ifname enp9s0 master br0
Enable the bridge to forward extensible authentication protocol over LAN (EAPOL) packets:
# nmcli connection modify br0 group-forward-mask 8
Configure the connection to automatically activate the ports:
# nmcli connection modify br0 connection.autoconnect-slaves 1
Activate the connection:
# nmcli connection up br0
Verification
Display the link status of Ethernet devices that are ports of a specific bridge:
# ip link show master br0 3: enp1s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel master br0 state UP mode DEFAULT group default qlen 1000 link/ether 52:54:00:62:61:0e brd ff:ff:ff:ff:ff:ff ...
Verify if forwarding of EAPOL packets is enabled on the
br0
device:# cat /sys/class/net/br0/bridge/group_fwd_mask 0x8
If the command returns
0x8
, forwarding is enabled.
Additional resources
-
nm-settings(5)
man page
33.3. Certificate requirements by FreeRADIUS
For a secure FreeRADIUS service, you require TLS certificates for different purposes:
A TLS server certificate for encrypted connections to the server. Use a trusted certificate authority (CA) to issue the certificate.
The server certificate requires the extended key usage (EKU) field set to
TLS Web Server Authentication
.Client certificates issued by the same CA for extended authentication protocol transport layer security (EAP-TLS). EAP-TLS provides certificate-based authentication and is enabled by default.
The client certificates require their EKU field set to
TLS Web Client Authentication
.
To secure connection, use your company’s CA or create your own CA to issue certificates for FreeRADIUS. If you use a public CA, you allow it to authenticate users and issue client certificates for EAP-TLS.
33.4. Creating a set of certificates on a FreeRADIUS server for testing purposes
For testing purposes, the freeradius
package installs scripts and configuration files in the /etc/raddb/certs/
directory to create your own certificate authority (CA) and issue certificates.
If you use the default configuration, certificates generated by these scripts expire after 60 days and keys use an insecure password ("whatever"). However, you can customize the CA, server, and client configuration.
After you perform the procedure, the following files, which you require later in this documentation, are created:
-
/etc/raddb/certs/ca.pem
: CA certificate -
/etc/raddb/certs/server.key
: Private key of the server certificate -
/etc/raddb/certs/server.pem
: Server certificate -
/etc/raddb/certs/client.key
: Private key of the client certificate -
/etc/raddb/certs/client.pem
: Client certificate
Prerequisites
-
You installed the
freeradius
package.
Procedure
Change into the
/etc/raddb/certs/
directory:# cd /etc/raddb/certs/
Optional: Customize the CA configuration in the
/etc/raddb/certs/ca.cnf
file:... [ req ] default_bits = 2048 input_password = ca_password output_password = ca_password ... [certificate_authority] countryName = US stateOrProvinceName = North Carolina localityName = Raleigh organizationName = Example Inc. emailAddress = admin@example.org commonName = "Example Certificate Authority" ...
Optional: Customize the server configuration in the
/etc/raddb/certs/server.cnf
file::... [ CA_default ] default_days = 730 ... [ req ] distinguished_name = server default_bits = 2048 input_password = key_password output_password = key_password ... [server] countryName = US stateOrProvinceName = North Carolina localityName = Raleigh organizationName = Example Inc. emailAddress = admin@example.org commonName = "Example Server Certificate" ...
Optional: Customize the client configuration in the
/etc/raddb/certs/client.cnf
file::... [ CA_default ] default_days = 365 ... [ req ] distinguished_name = client default_bits = 2048 input_password = password_on_private_key output_password = password_on_private_key ... [client] countryName = US stateOrProvinceName = North Carolina localityName = Raleigh organizationName = Example Inc. emailAddress = user@example.org commonName = user@example.org ...
Create the certificates:
# make all
Change the group on the
/etc/raddb/certs/server.pem
file toradiusd
:# chgrp radiusd /etc/raddb/certs/server.pem
Additional resources
-
/etc/raddb/certs/README.md
33.5. Configuring FreeRADIUS to authenticate network clients securely by using EAP
FreeRADIUS supports different methods of the Extensible authentication protocol (EAP). However, for a secure network, configure FreeRADIUS to support only the following secure EAP authentication methods:
- EAP-TLS (transport layer security) uses a secure TLS connection to authenticate clients by using certificates. To use EAP-TLS, you need TLS client certificates for each network client and a server certificate for the server. Note that the same certificate authority (CA) must have issued the certificates. Always use your own CA to create certificates, because all client certificates issued by the CA you use can authenticate to your FreeRADIUS server.
- EAP-TTLS (tunneled transport layer security) uses a secure TLS connection as the outer authentication protocol to set up the tunnel. The inner authentication then uses, for example, the password authentication protocol (PAP) or challenge handshake authentication protocol (CHAP). To use EAP-TTLS, you need a TLS server certificate.
- EAP-PEAP (protected extensible authentication protocol) uses a secure TLS connection as the outer authentication protocol to set up the tunnel. The authenticator authenticates the certificate of the RADIUS server. Afterwards, the supplicant authenticates through the encrypted tunnel by using Microsoft challenge handshake authentication protocol version 2 (MS-CHAPv2) or other methods.
The default FreeRADIUS configuration files serve as documentation and describe all parameters and directives. If you want to disable certain features, comment them out instead of removing the corresponding parts in the configuration files. This enables you to preserve the structure of the configuration files and the included documentation.
Prerequisites
-
You installed the
freeradius
package. -
The configuration files in the
/etc/raddb/
directory are unchanged and as provided by thefreeradius
package. The following files exist on the server:
-
TLS private key of the FreeRADIUS host:
/etc/raddb/certs/server.key
-
TLS server certificate of the FreeRADIUS host:
/etc/raddb/certs/server.pem
-
TLS CA certificate:
/etc/raddb/certs/ca.pem
If you store the files in a different location or if they have different names, set the
private_key_file
,certificate_file
, andca_file
parameters in the/etc/raddb/mods-available/eap
file accordingly.-
TLS private key of the FreeRADIUS host:
Procedure
If the
/etc/raddb/certs/dh
with Diffie-Hellman (DH) parameters does not exist, create one. For example, to create a DH file with a 2048 bits prime, enter:# openssl dhparam -out /etc/raddb/certs/dh 2048
For security reasons, do not use a DH file with less than a 2048 bits prime. Depending on the number of bits, the creation of the file can take several minutes.
Set secure permissions on the TLS private key, server certificate, CA certificate, and the file with DH parameters:
# chmod 640 /etc/raddb/certs/server.key /etc/raddb/certs/server.pem /etc/raddb/certs/ca.pem /etc/raddb/certs/dh # chown root:radiusd /etc/raddb/certs/server.key /etc/raddb/certs/server.pem /etc/raddb/certs/ca.pem /etc/raddb/certs/dh
Edit the
/etc/raddb/mods-available/eap
file:Set the password of the private key in the
private_key_password
parameter:eap { ... tls-config tls-common { ... private_key_password = key_password ... } }
Depending on your environment, set the
default_eap_type
parameter in theeap
directive to your primary EAP type you use:eap { ... default_eap_type = ttls ... }
For a secure environment, use only
ttls
,tls
, orpeap
.Comment out the
md5
directives to disable the insecure EAP-MD5 authentication method:eap { ... # md5 { # } ... }
Note that, in the default configuration file, other insecure EAP authentication methods are commented out by default.
Edit the
/etc/raddb/sites-available/default
file, and comment out all authentication methods other thaneap
:authenticate { ... # Auth-Type PAP { # pap # } # Auth-Type CHAP { # chap # } # Auth-Type MS-CHAP { # mschap # } # mschap # digest ... }
This leaves only EAP enabled for the outer authentication and disables plain-text authentication methods.
Edit the
/etc/raddb/clients.conf
file:Set a secure password in the
localhost
andlocalhost_ipv6
client directives:client localhost { ipaddr = 127.0.0.1 ... secret = localhost_client_password ... } client localhost_ipv6 { ipv6addr = ::1 secret = localhost_client_password }
Add a client directive for the network authenticator:
client hostapd.example.org { ipaddr = 192.0.2.2/32 secret = hostapd_client_password }
Optional: If other hosts should also be able to access the FreeRADIUS service, add client directives for them as well, for example:
client <hostname_or_description> { ipaddr = <IP_address_or_range> secret = <client_password> }
The
ipaddr
parameter accepts IPv4 and IPv6 addresses, and you can use the optional classless inter-domain routing (CIDR) notation to specify ranges. However, you can set only one value in this parameter. For example, to grant access to both an IPv4 and IPv6 address, you must add two client directives.Use a descriptive name for the client directive, such as a hostname or a word that describes where the IP range is used.
If you want to use EAP-TTLS or EAP-PEAP, add the users to the
/etc/raddb/users
file:example_user Cleartext-Password := "user_password"
For users who should use certificate-based authentication (EAP-TLS), do not add any entry.
Verify the configuration files:
# radiusd -XC ... Configuration appears to be OK
Open the RADIUS ports in the
firewalld
service:# firewall-cmd --permanent --add-service=radius # firewall-cmd --reload
Enable and start the
radiusd
service:# systemctl enable --now radiusd
Verification
Troubleshooting
Stop the
radiusd
service:# systemctl stop radiusd
Start the service in debug mode:
# radiusd -X ... Ready to process requests
-
Perform authentication tests on the FreeRADIUS host, as referenced in the
Verification
section.
Next steps
- Disable no longer required authentication methods and other features you do not use.
33.6. Configuring hostapd
as an authenticator in a wired network
The host access point daemon (hostapd
) service can act as an authenticator in a wired network to provide 802.1X authentication. For this, the hostapd
service requires a RADIUS server that authenticates the clients.
The hostapd
service provides an integrated RADIUS server. However, use the integrated RADIUS server only for testing purposes. For production environments, use FreeRADIUS server, which supports additional features, such as different authentication methods and access control.
The hostapd
service does not interact with the traffic plane. The service acts only as an authenticator. For example, use a script or service that uses the hostapd
control interface to allow or deny traffic based on the result of authentication events.
Prerequisites
-
You installed the
hostapd
package. - The FreeRADIUS server has been configured, and it is ready to authenticate clients.
Procedure
Create the
/etc/hostapd/hostapd.conf
file with the following content:# General settings of hostapd # =========================== # Control interface settings ctrl_interface=/var/run/hostapd ctrl_interface_group=wheel # Enable logging for all modules logger_syslog=-1 logger_stdout=-1 # Log level logger_syslog_level=2 logger_stdout_level=2 # Wired 802.1X authentication # =========================== # Driver interface type driver=wired # Enable IEEE 802.1X authorization ieee8021x=1 # Use port access entry (PAE) group address # (01:80:c2:00:00:03) when sending EAPOL frames use_pae_group_addr=1 # Network interface for authentication requests interface=br0 # RADIUS client configuration # =========================== # Local IP address used as NAS-IP-Address own_ip_addr=192.0.2.2 # Unique NAS-Identifier within scope of RADIUS server nas_identifier=hostapd.example.org # RADIUS authentication server auth_server_addr=192.0.2.1 auth_server_port=1812 auth_server_shared_secret=hostapd_client_password # RADIUS accounting server acct_server_addr=192.0.2.1 acct_server_port=1813 acct_server_shared_secret=hostapd_client_password
For further details about the parameters used in this configuration, see their descriptions in the
/usr/share/doc/hostapd/hostapd.conf
example configuration file.Enable and start the
hostapd
service:# systemctl enable --now hostapd
Verification
See:
Troubleshooting
Stop the
hostapd
service:# systemctl stop hostapd
Start the service in debug mode:
# hostapd -d /etc/hostapd/hostapd.conf
-
Perform authentication tests on the FreeRADIUS host, as referenced in the
Verification
section.
Additional resources
-
hostapd.conf(5)
man page -
/usr/share/doc/hostapd/hostapd.conf
file
33.7. Testing EAP-TTLS authentication against a FreeRADIUS server or authenticator
To test if authentication by using extensible authentication protocol (EAP) over tunneled transport layer security (EAP-TTLS) works as expected, run this procedure:
- After you set up the FreeRADIUS server
-
After you set up the
hostapd
service as an authenticator for 802.1X network authentication.
The output of the test utilities used in this procedure provide additional information about the EAP communication and help you to debug problems.
Prerequisites
When you want to authenticate to:
A FreeRADIUS server:
-
The
eapol_test
utility, provided by thehostapd
package, is installed. - The client, on which you run this procedure, has been authorized in the FreeRADIUS server’s client databases.
-
The
-
An authenticator, the
wpa_supplicant
utility, provided by the same-named package, is installed.
-
You stored the certificate authority (CA) certificate in the
/etc/pki/tls/certs/ca.pem
file.
Procedure
Create the
/etc/wpa_supplicant/wpa_supplicant-TTLS.conf
file with the following content:ap_scan=0 network={ eap=TTLS eapol_flags=0 key_mgmt=IEEE8021X # Anonymous identity (sent in unencrypted phase 1) # Can be any string anonymous_identity="anonymous" # Inner authentication (sent in TLS-encrypted phase 2) phase2="auth=PAP" identity="example_user" password="user_password" # CA certificate to validate the RADIUS server's identity ca_cert="/etc/pki/tls/certs/ca.pem" }
To authenticate to:
A FreeRADIUS server, enter:
# eapol_test -c /etc/wpa_supplicant/wpa_supplicant-TTLS.conf -a 192.0.2.1 -s <client_password> ... EAP: Status notification: remote certificate verification (param=success) ... CTRL-EVENT-EAP-SUCCESS EAP authentication completed successfully ... SUCCESS
The
-a
option defines the IP address of the FreeRADIUS server, and the-s
option specifies the password for the host on which you run the command in the FreeRADIUS server’s client configuration.An authenticator, enter:
# wpa_supplicant -c /etc/wpa_supplicant/wpa_supplicant-TTLS.conf -D wired -i enp0s31f6 ... enp0s31f6: CTRL-EVENT-EAP-SUCCESS EAP authentication completed successfully ...
The
-i
option specifies the network interface name on whichwpa_supplicant
sends out extended authentication protocol over LAN (EAPOL) packets.For more debugging information, pass the
-d
option to the command.
Additional resources
-
/usr/share/doc/wpa_supplicant/wpa_supplicant.conf
file
33.8. Testing EAP-TLS authentication against a FreeRADIUS server or authenticator
To test if authentication by using extensible authentication protocol (EAP) transport layer security (EAP-TLS) works as expected, run this procedure:
- After you set up the FreeRADIUS server
-
After you set up the
hostapd
service as an authenticator for 802.1X network authentication.
The output of the test utilities used in this procedure provide additional information about the EAP communication and help you to debug problems.
Prerequisites
When you want to authenticate to:
A FreeRADIUS server:
-
The
eapol_test
utility, provided by thehostapd
package, is installed. - The client, on which you run this procedure, has been authorized in the FreeRADIUS server’s client databases.
-
The
-
An authenticator, the
wpa_supplicant
utility, provided by the same-named package, is installed.
-
You stored the certificate authority (CA) certificate in the
/etc/pki/tls/certs/ca.pem
file. - The CA that issued the client certificate is the same that issued the server certificate of the FreeRADIUS server.
-
You stored the client certificate in the
/etc/pki/tls/certs/client.pem
file. -
You stored the private key of the client in the
/etc/pki/tls/private/client.key
Procedure
Create the
/etc/wpa_supplicant/wpa_supplicant-TLS.conf
file with the following content:ap_scan=0 network={ eap=TLS eapol_flags=0 key_mgmt=IEEE8021X identity="user@example.org" client_cert="/etc/pki/tls/certs/client.pem" private_key="/etc/pki/tls/private/client.key" private_key_passwd="password_on_private_key" # CA certificate to validate the RADIUS server's identity ca_cert="/etc/pki/tls/certs/ca.pem" }
To authenticate to:
A FreeRADIUS server, enter:
# eapol_test -c /etc/wpa_supplicant/wpa_supplicant-TLS.conf -a 192.0.2.1 -s <client_password> ... EAP: Status notification: remote certificate verification (param=success) ... CTRL-EVENT-EAP-SUCCESS EAP authentication completed successfully ... SUCCESS
The
-a
option defines the IP address of the FreeRADIUS server, and the-s
option specifies the password for the host on which you run the command in the FreeRADIUS server’s client configuration.An authenticator, enter:
# wpa_supplicant -c /etc/wpa_supplicant/wpa_supplicant-TLS.conf -D wired -i enp0s31f6 ... enp0s31f6: CTRL-EVENT-EAP-SUCCESS EAP authentication completed successfully ...
The
-i
option specifies the network interface name on whichwpa_supplicant
sends out extended authentication protocol over LAN (EAPOL) packets.For more debugging information, pass the
-d
option to the command.
Additional resources
-
/usr/share/doc/wpa_supplicant/wpa_supplicant.conf
file
33.9. Blocking and allowing traffic based on hostapd
authentication events
The hostapd
service does not interact with the traffic plane. The service acts only as an authenticator. However, you can write a script to allow and deny traffic based on the result of authentication events.
This procedure is not supported and is no enterprise-ready solution. It only demonstrates how to block or allow traffic by evaluating events retrieved by hostapd_cli
.
When the 802-1x-tr-mgmt
systemd service starts, RHEL blocks all traffic on the listen port of hostapd
except extensible authentication protocol over LAN (EAPOL) packets and uses the hostapd_cli
utility to connect to the hostapd
control interface. The /usr/local/bin/802-1x-tr-mgmt
script then evaluates events. Depending on the different events received by hostapd_cli
, the script allows or blocks traffic for MAC addresses. Note that, when the 802-1x-tr-mgmt
service stops, all traffic is automatically allowed again.
Perform this procedure on the hostapd
server.
Prerequisites
-
The
hostapd
service has been configured, and the service is ready to authenticate clients.
Procedure
Create the
/usr/local/bin/802-1x-tr-mgmt
file with the following content:#!/bin/sh if [ "x$1" == "xblock_all" ] then nft delete table bridge tr-mgmt-br0 2>/dev/null || true nft -f - << EOF table bridge tr-mgmt-br0 { set allowed_macs { type ether_addr } chain accesscontrol { ether saddr @allowed_macs accept ether daddr @allowed_macs accept drop } chain forward { type filter hook forward priority 0; policy accept; meta ibrname "br0" jump accesscontrol } } EOF echo "802-1x-tr-mgmt Blocking all traffic through br0. Traffic for given host will be allowed after 802.1x authentication" elif [ "x$1" == "xallow_all" ] then nft delete table bridge tr-mgmt-br0 echo "802-1x-tr-mgmt Allowed all forwarding again" fi case ${2:-NOTANEVENT} in AP-STA-CONNECTED | CTRL-EVENT-EAP-SUCCESS | CTRL-EVENT-EAP-SUCCESS2) nft add element bridge tr-mgmt-br0 allowed_macs { $3 } echo "$1: Allowed traffic from $3" ;; AP-STA-DISCONNECTED | CTRL-EVENT-EAP-FAILURE) nft delete element bridge tr-mgmt-br0 allowed_macs { $3 } echo "802-1x-tr-mgmt $1: Denied traffic from $3" ;; esac
Create the
/etc/systemd/system/802-1x-tr-mgmt@.service
systemd service file with the following content:[Unit] Description=Example 802.1x traffic management for hostapd After=hostapd.service After=sys-devices-virtual-net-%i.device [Service] Type=simple ExecStartPre=-/bin/sh -c '/usr/sbin/tc qdisc del dev %i ingress > /dev/null 2>&1' ExecStartPre=-/bin/sh -c '/usr/sbin/tc qdisc del dev %i clsact > /dev/null 2>&1' ExecStartPre=/usr/sbin/tc qdisc add dev %i clsact ExecStartPre=/usr/sbin/tc filter add dev %i ingress pref 10000 protocol 0x888e matchall action ok index 100 ExecStartPre=/usr/sbin/tc filter add dev %i ingress pref 10001 protocol all matchall action drop index 101 ExecStart=/usr/sbin/hostapd_cli -i %i -a /usr/local/bin/802-1x-tr-mgmt ExecStopPost=-/usr/sbin/tc qdisc del dev %i clsact [Install] WantedBy=multi-user.target
Reload systemd:
# systemctl daemon-reload
Enable and start the
802-1x-tr-mgmt
service with the interface namehostapd
is listening on:# systemctl enable --now 802-1x-tr-mgmt@br0.service
Verification
Authenticate with a client to the network. See:
Additional resources
-
systemd.service(5)
man page
Chapter 34. Getting started with Multipath TCP
Transmission Control Protocol (TCP) ensures reliable delivery of the data through the internet and automatically adjusts its bandwidth in response to network load. Multipath TCP (MPTCP) is an extension to the original TCP protocol (single-path). MPTCP enables a transport connection to operate across multiple paths simultaneously, and brings network connection redundancy to user endpoint devices.
34.1. Understanding MPTCP
The Multipath TCP (MPTCP) protocol allows for simultaneous usage of multiple paths between connection endpoints. The protocol design improves connection stability and also brings other benefits compared to the single-path TCP.
In MPTCP terminology, links are considered as paths.
The following are some of the advantages of using MPTCP:
- It allows a connection to simultaneously use multiple network interfaces.
- In case a connection is bound to a link speed, the usage of multiple links can increase the connection throughput. Note, that in case of the connection is bound to a CPU, the usage of multiple links causes the connection slowdown.
- It increases the resilience to link failures.
For more details about MPTCP, review the Additional resources.
34.2. Preparing RHEL to enable MPTCP support
By default the MPTCP support is disabled in RHEL. Enable MPTCP so that applications that support this feature can use it. Additionally, you have to configure user space applications to force use MPTCP sockets if those applications have TCP sockets by default.
You can use the sysctl
utility to enable MPTCP support and prepare RHEL for enabling MPTCP for applications system-wide using a SystemTap
script.
Prerequisites
The following packages are installed:
-
systemtap
-
iperf3
Procedure
Enable MPTCP sockets in the kernel:
# echo "net.mptcp.enabled=1" > /etc/sysctl.d/90-enable-MPTCP.conf # sysctl -p /etc/sysctl.d/90-enable-MPTCP.conf
Verify that MPTCP is enabled in the kernel:
# sysctl -a | grep mptcp.enabled net.mptcp.enabled = 1
Create a
mptcp-app.stap
file with the following content:#!/usr/bin/env stap %{ #include <linux/in.h> #include <linux/ip.h> %} /* RSI contains 'type' and RDX contains 'protocol'. */ function mptcpify () %{ if (CONTEXT->kregs->si == SOCK_STREAM && (CONTEXT->kregs->dx == IPPROTO_TCP || CONTEXT->kregs->dx == 0)) { CONTEXT->kregs->dx = IPPROTO_MPTCP; STAP_RETVALUE = 1; } else { STAP_RETVALUE = 0; } %} probe kernel.function("__sys_socket") { if (mptcpify() == 1) { printf("command %16s mptcpified\n", execname()); } }
Force user space applications to create MPTCP sockets instead of TCP ones:
# stap -vg mptcp-app.stap
Note: This operation affects all TCP sockets which are started after the command. The applications will continue using TCP sockets after you interrupt the command above with Ctrl+C.
Alternatively, to allow MPTCP usage to only specific application, you can modify the
mptcp-app.stap
file with the following content:#!/usr/bin/env stap %{ #include <linux/in.h> #include <linux/ip.h> %} /* according to [1], RSI contains 'type' and RDX * contains 'protocol'. * [1] https://github.com/torvalds/linux/blob/master/arch/x86/entry/entry_64.S#L79 */ function mptcpify () %{ if (CONTEXT->kregs->si == SOCK_STREAM && (CONTEXT->kregs->dx == IPPROTO_TCP || CONTEXT->kregs->dx == 0)) { CONTEXT->kregs->dx = IPPROTO_MPTCP; STAP_RETVALUE = 1; } else { STAP_RETVALUE = 0; } %} probe kernel.function("__sys_socket") { cur_proc = execname() if ((cur_proc == @1) && (mptcpify() == 1)) { printf("command %16s mptcpified\n", cur_proc); } }
In case of alternative choice, assuming, you want to force the
iperf3
tool to use MPTCP instead of TCP. To do so, enter the following command:# stap -vg mptcp-app.stap iperf3
After the
mptcp-app.stap
script installs the kernel probe, the following warnings appear in the kerneldmesg
output# dmesg ... [ 1752.694072] Kprobes globally unoptimized [ 1752.730147] stap_1ade3b3356f3e68765322e26dec00c3d_1476: module_layout: kernel tainted. [ 1752.732162] Disabling lock debugging due to kernel taint [ 1752.733468] stap_1ade3b3356f3e68765322e26dec00c3d_1476: loading out-of-tree module taints kernel. [ 1752.737219] stap_1ade3b3356f3e68765322e26dec00c3d_1476: module verification failed: signature and/or required key missing - tainting kernel [ 1752.737219] stap_1ade3b3356f3e68765322e26dec00c3d_1476 (mptcp-app.stap): systemtap: 4.5/0.185, base: ffffffffc0550000, memory: 224data/32text/57ctx/65638net/367alloc kb, probes: 1
Start the
iperf3
server:# iperf3 -s Server listening on 5201
Connect the client to the server:
# iperf3 -c 127.0.0.1 -t 3
After the connection is established, verify the
ss
output to see the subflow-specific status:# ss -nti '( dport :5201 )' State Recv-Q Send-Q Local Address:Port Peer Address:Port Process ESTAB 0 0 127.0.0.1:41842 127.0.0.1:5201 cubic wscale:7,7 rto:205 rtt:4.455/8.878 ato:40 mss:21888 pmtu:65535 rcvmss:536 advmss:65483 cwnd:10 bytes_sent:141 bytes_acked:142 bytes_received:4 segs_out:8 segs_in:7 data_segs_out:3 data_segs_in:3 send 393050505bps lastsnd:2813 lastrcv:2772 lastack:2772 pacing_rate 785946640bps delivery_rate 10944000000bps delivered:4 busy:41ms rcv_space:43690 rcv_ssthresh:43690 minrtt:0.008 tcp-ulp-mptcp flags:Mmec token:0000(id:0)/2ff053ec(id:0) seq:3e2cbea12d7673d4 sfseq:3 ssnoff:ad3d00f4 maplen:2
Verify MPTCP counters:
# nstat MPTcp* #kernel MPTcpExtMPCapableSYNRX 2 0.0 MPTcpExtMPCapableSYNTX 2 0.0 MPTcpExtMPCapableSYNACKRX 2 0.0 MPTcpExtMPCapableACKRX 2 0.0
Additional resources
- How can I download or install debuginfo packages for RHEL systems?
-
tcp(7)
man page -
mptcpize(8)
man page
34.3. Using iproute2 to temporarily configure and enable multiple paths for MPTCP applications
Each MPTCP connection uses a single subflow similar to plain TCP. To get the MPTCP benefits, specify a higher limit for maximum number of subflows for each MPTCP connection. Then configure additional endpoints to create those subflows.
The configuration in this procedure will not persist after rebooting your machine.
Note that MPTCP does not yet support mixed IPv6 and IPv4 endpoints for the same socket. Use endpoints belonging to the same address family.
Prerequisites
-
The
iperf3
package is installed Server network interface settings:
-
enp4s0:
192.0.2.1/24
-
enp1s0:
198.51.100.1/24
-
enp4s0:
Client network interface settings:
-
enp4s0f0:
192.0.2.2/24
-
enp4s0f1:
198.51.100.2/24
-
enp4s0f0:
Procedure
Configure the client to accept up to 1 additional remote address, as provided by the server:
# ip mptcp limits set add_addr_accepted 1
Add IP address
198.51.100.1
as a new MPTCP endpoint on the server:# ip mptcp endpoint add 198.51.100.1 dev enp1s0 signal
The
signal
option ensures that theADD_ADDR
packet is sent after the three-way-handshake.Start the
iperf3
server:# iperf3 -s Server listening on 5201
Connect the client to the server:
# iperf3 -c 192.0.2.1 -t 3
Verification
Verify the connection is established:
# ss -nti '( sport :5201 )'
Verify the connection and IP address limit:
# ip mptcp limit show
Verify the newly added endpoint:
# ip mptcp endpoint show
Verify MPTCP counters by using the
nstat MPTcp*
command on a server:# nstat MPTcp* #kernel MPTcpExtMPCapableSYNRX 2 0.0 MPTcpExtMPCapableACKRX 2 0.0 MPTcpExtMPJoinSynRx 2 0.0 MPTcpExtMPJoinAckRx 2 0.0 MPTcpExtEchoAdd 2 0.0
Additional resources
-
ip-mptcp(8)
man page -
mptcpize(8)
man page
34.4. Permanently configuring multiple paths for MPTCP applications
You can configure MultiPath TCP (MPTCP) using the nmcli
command to permanently establish multiple subflows between a source and destination system. The subflows can use different resources, different routes to the destination, and even different networks. Such as Ethernet, cellular, wifi, and so on. As a result, you achieve combined connections, which increase network resilience and throughput.
The server uses the following network interfaces in our example:
-
enp4s0:
192.0.2.1/24
-
enp1s0:
198.51.100.1/24
-
enp7s0:
192.0.2.3/24
The client uses the following network interfaces in our example:
-
enp4s0f0:
192.0.2.2/24
-
enp4s0f1:
198.51.100.2/24
-
enp6s0:
192.0.2.5/24
Prerequisites
- You configured the default gateway on the relevant interfaces.
Procedure
Enable MPTCP sockets in the kernel:
# echo "net.mptcp.enabled=1" > /etc/sysctl.d/90-enable-MPTCP.conf # sysctl -p /etc/sysctl.d/90-enable-MPTCP.conf
Optional: The RHEL kernel default for subflow limit is 2. If you require more:
Create the
/etc/systemd/system/set_mptcp_limit.service
file with the following content:[Unit] Description=Set MPTCP subflow limit to 3 After=network.target [Service] ExecStart=ip mptcp limits set subflows 3 Type=oneshot [Install] WantedBy=multi-user.target
The oneshot unit executes the
ip mptcp limits set subflows 3
command after your network (network.target
) is operational during every boot process.The
ip mptcp limits set subflows 3
command sets the maximum number of additional subflows for each connection, so 4 in total. It is possible to add maximally 3 additional subflows.Enable the
set_mptcp_limit
service:# systemctl enable --now set_mptcp_limit
Enable MPTCP on all connection profiles that you want to use for connection aggregation:
# nmcli connection modify <profile_name> connection.mptcp-flags signal,subflow,also-without-default-route
The
connection.mptcp-flags
parameter configures MPTCP endpoints and the IP address flags. If MPTCP is enabled in a NetworkManager connection profile, the setting will configure the IP addresses of the relevant network interface as MPTCP endpoints.By default, NetworkManager does not add MPTCP flags to IP addresses if there is no default gateway. If you want to bypass that check, you need to use also the
also-without-default-route
flag.
Verification
Verify that you enabled the MPTCP kernel parameter:
# sysctl net.mptcp.enabled net.mptcp.enabled = 1
Verify that you set the subflow limit correctly, in case the default was not enough:
# ip mptcp limit show add_addr_accepted 2 subflows 3
Verify that you configured the per-address MPTCP setting correctly:
# ip mptcp endpoint show 192.0.2.1 id 1 subflow dev enp4s0 198.51.100.1 id 2 subflow dev enp1s0 192.0.2.3 id 3 subflow dev enp7s0 192.0.2.4 id 4 subflow dev enp3s0 ...
Additional resources
-
nm-settings-nmcli(5)
-
ip-mptcp(8)
- Section 34.1, “Understanding MPTCP”
- Understanding Multipath TCP: High availability for endpoints and the networking highway of the future
- RFC8684: TCP Extensions for Multipath Operation with Multiple Addresses
- Using Multipath TCP to better survive outages and increase bandwidth
34.5. Monitoring MPTCP sub-flows
The life cycle of a multipath TCP (MPTCP) socket can be complex: The main MPTCP socket is created, the MPTCP path is validated, one or more sub-flows are created and eventually removed. Finally, the MPTCP socket is terminated.
The MPTCP protocol allows monitoring MPTCP-specific events related to socket and sub-flow creation and deletion, using the ip
utility provided by the iproute
package. This utility uses the netlink
interface to monitor MPTCP events.
This procedure demonstrates how to monitor MPTCP events. For that, it simulates a MPTCP server application, and a client connects to this service. The involved clients in this example use the following interfaces and IP addresses:
-
Server:
192.0.2.1
-
Client (Ethernet connection):
192.0.2.2
-
Client (WiFi connection):
192.0.2.3
To simplify this example, all interfaces are within the same subnet. This is not a requirement. However, it is important that routing has been configured correctly, and the client can reach the server via both interfaces.
Prerequisites
- A RHEL client with two network interfaces, such as a laptop with Ethernet and WiFi
- The client can connect to the server via both interfaces
- A RHEL server
- Both the client and the server run RHEL 8.6 or later
Procedure
Set the per connection additional subflow limits to
1
on both client and server:# ip mptcp limits set add_addr_accepted 0 subflows 1
On the server, to simulate a MPTCP server application, start
netcat
(nc
) in listen mode with enforced MPTCP sockets instead of TCP sockets:# nc -l -k -p 12345
The
-k
option causes thatnc
does not close the listener after the first accepted connection. This is required to demonstrate the monitoring of sub-flows.On the client:
Identify the interface with the lowest metric:
# ip -4 route 192.0.2.0/24 dev enp1s0 proto kernel scope link src 192.0.2.2 metric 100 192.0.2.0/24 dev wlp1s0 proto kernel scope link src 192.0.2.3 metric 600
The
enp1s0
interface has a lower metric thanwlp1s0
. Therefore, RHEL usesenp1s0
by default.On the first terminal, start the monitoring:
# ip mptcp monitor
On the second terminal, start a MPTCP connection to the server:
# nc 192.0.2.1 12345
RHEL uses the
enp1s0
interface and its associated IP address as a source for this connection.On the monitoring terminal, the
ip mptcp monitor
command now logs:[ CREATED] token=63c070d2 remid=0 locid=0 saddr4=192.0.2.2 daddr4=192.0.2.1 sport=36444 dport=12345
The token identifies the MPTCP socket as an unique ID, and later it enables you to correlate MPTCP events on the same socket.
On the terminal with the running
nc
connection to the server, press Enter. This first data packet fully establishes the connection. Note that, as long as no data has been sent, the connection is not established.On the monitoring terminal,
ip mptcp monitor
now logs:[ ESTABLISHED] token=63c070d2 remid=0 locid=0 saddr4=192.0.2.2 daddr4=192.0.2.1 sport=36444 dport=12345
Optional: Display the connections to port
12345
on the server:# ss -taunp | grep ":12345" tcp ESTAB 0 0 192.0.2.2:36444 192.0.2.1:12345
At this point, only one connection to the server has been established.
On a third terminal, create another endpoint:
# ip mptcp endpoint add dev wlp1s0 192.0.2.3 subflow
This command sets the name and IP address of the WiFi interface of the client in this command.
On the monitoring terminal,
ip mptcp monitor
now logs:[SF_ESTABLISHED] token=63c070d2 remid=0 locid=2 saddr4=192.0.2.3 daddr4=192.0.2.1 sport=53345 dport=12345 backup=0 ifindex=3
The
locid
field displays the local address ID of the new sub-flow and identifies this sub-flow even if the connection uses network address translation (NAT). Thesaddr4
field matches the endpoint’s IP address from theip mptcp endpoint add
command.Optional: Display the connections to port
12345
on the server:# ss -taunp | grep ":12345" tcp ESTAB 0 0 192.0.2.2:36444 192.0.2.1:12345 tcp ESTAB 0 0 192.0.2.3%wlp1s0:53345 192.0.2.1:12345
The command now displays two connections:
-
The connection with source address
192.0.2.2
corresponds to the first MPTCP sub-flow that you established previously. -
The connection from the sub-flow over the
wlp1s0
interface with source address192.0.2.3
.
-
The connection with source address
On the third terminal, delete the endpoint:
# ip mptcp endpoint delete id 2
Use the ID from the
locid
field from theip mptcp monitor
output, or retrieve the endpoint ID using theip mptcp endpoint show
command.On the monitoring terminal,
ip mptcp monitor
now logs:[ SF_CLOSED] token=63c070d2 remid=0 locid=2 saddr4=192.0.2.3 daddr4=192.0.2.1 sport=53345 dport=12345 backup=0 ifindex=3
On the first terminal with the
nc
client, press Ctrl+C to terminate the session.On the monitoring terminal,
ip mptcp monitor
now logs:[ CLOSED] token=63c070d2
Additional resources
-
ip-mptcp(1)
man page - How NetworkManager manages multiple default gateways
34.6. Disabling Multipath TCP in the kernel
You can explicitly disable the MPTCP option in the kernel.
Procedure
Disable the
mptcp.enabled
option.# echo "net.mptcp.enabled=0" > /etc/sysctl.d/90-enable-MPTCP.conf # sysctl -p /etc/sysctl.d/90-enable-MPTCP.conf
Verification
Verify whether the
mptcp.enabled
is disabled in the kernel.# sysctl -a | grep mptcp.enabled net.mptcp.enabled = 0
Chapter 35. Legacy network scripts support in RHEL
By default, RHEL uses NetworkManager to configure and manage network connections, and the /usr/sbin/ifup
and /usr/sbin/ifdown
scripts use NetworkManager to process ifcfg
files in the /etc/sysconfig/network-scripts/
directory.
The legacy scripts are deprecated in RHEL 8 and will be removed in a future major version of RHEL. If you still use the legacy network scripts, for example, because you upgraded from an earlier version to RHEL 8, Red Hat recommends that you migrate your configuration to NetworkManager.
35.1. Installing the legacy network scripts
If you require the deprecated network scripts that processes the network configuration without using NetworkManager, you can install them. In this case, the /usr/sbin/ifup
and /usr/sbin/ifdown
scripts link to the deprecated shell scripts that manage the network configuration.
Procedure
Install the
network-scripts
package:# yum install network-scripts
Chapter 36. Configuring ip networking with ifcfg files
Interface configuration (ifcfg
) files control the software interfaces for individual network devices. As the system boots, it uses these files to determine what interfaces to bring up and how to configure them. These files are named ifcfg-name_pass
, where the suffix name refers to the name of the device that the configuration file controls. By convention, the ifcfg
file’s suffix is the same as the string given by the DEVICE
directive in the configuration file itself.
NetworkManager supports profiles stored in the keyfile format. However, by default, NetworkManager uses the ifcfg
format when you use the NetworkManager API to create or update profiles.
In a future major RHEL release, the keyfile format will be default. Consider using the keyfile format if you want to manually create and manage configuration files. For details, see NetworkManager connection profiles in keyfile format.
36.1. Configuring an interface with static network settings using ifcfg files
If you do not use the NetworkManager utilities and applications, you can manually configure a network interface by creating ifcfg
files.
Procedure
To configure an interface with static network settings using
ifcfg
files, for an interface with the nameenp1s0
, create a file with the nameifcfg-enp1s0
in the/etc/sysconfig/network-scripts/
directory that contains:For
IPv4
configuration:DEVICE=enp1s0 BOOTPROTO=none ONBOOT=yes PREFIX=24 IPADDR=192.0.2.1 GATEWAY=192.0.2.254
For
IPv6
configuration:DEVICE=enp1s0 BOOTPROTO=none ONBOOT=yes IPV6INIT=yes IPV6ADDR=2001:db8:1::2/64
Additional resources
-
nm-settings-ifcfg-rh(5)
man page
36.2. Configuring an interface with dynamic network settings using ifcfg files
If you do not use the NetworkManager utilities and applications, you can manually configure a network interface by creating ifcfg
files.
Procedure
To configure an interface named em1 with dynamic network settings using
ifcfg
files, create a file with the nameifcfg-em1
in the/etc/sysconfig/network-scripts/
directory that contains:DEVICE=em1 BOOTPROTO=dhcp ONBOOT=yes
To configure an interface to send:
A different host name to the
DHCP
server, add the following line to theifcfg
file:DHCP_HOSTNAME=hostname
A different fully qualified domain name (FQDN) to the
DHCP
server, add the following line to theifcfg
file:DHCP_FQDN=fully.qualified.domain.name
NoteYou can use only one of these settings. If you specify both
DHCP_HOSTNAME
andDHCP_FQDN
, onlyDHCP_FQDN
is used.To configure an interface to use particular
DNS
servers, add the following lines to theifcfg
file:PEERDNS=no DNS1=ip-address DNS2=ip-address
where ip-address is the address of a
DNS
server. This will cause the network service to update/etc/resolv.conf
with the specifiedDNS
servers specified. Only oneDNS
server address is necessary, the other is optional.
36.3. Managing system-wide and private connection profiles with ifcfg files
By default, all users on a host can use the connections defined in ifcfg
files. You can limit this behavior to specific users by adding the USERS
parameter to the ifcfg
file.
Prerequisite
-
The
ifcfg
file already exists.
Procedure
Edit the
ifcfg
file in the/etc/sysconfig/network-scripts/
directory that you want to limit to certain users, and add:USERS="username1 username2 ..."
Reactive the connection:
# nmcli connection up connection_name
Chapter 37. NetworkManager connection profiles in keyfile format
By default, NetworkManager stores connection profiles in ifcfg
format, but you can also use profiles in keyfile format. Unlike the deprecated ifcfg
format, the keyfile format supports all connection settings that NetworkManager provides.
In the Red Hat Enterprise Linux 9, the keyfile format will be the default.
37.1. The keyfile format of NetworkManager profiles
The keyfile format is similar to the INI format. For example, the following is an Ethernet connection profile in keyfile format:
[connection] id=example_connection uuid=82c6272d-1ff7-4d56-9c7c-0eb27c300029 type=ethernet autoconnect=true [ipv4] method=auto [ipv6] method=auto [ethernet] mac-address=00:53:00:8f:fa:66
Typos or incorrect placements of parameters can lead to unexpected behavior. Therefore, do not manually edit or create NetworkManager profiles.
Use the nmcli
utility, the network
RHEL system role, or the nmstate
API to manage NetworkManager connections. For example, you can use the nmcli
utility in offline mode to create connection profiles.
Each section corresponds to a NetworkManager setting name as described in the nm-settings(5)
and nm-settings-keyfile(5)
man pages. Each key-value-pair in a section is one of the properties listed in the settings specification of the man page.
Most variables in NetworkManager keyfiles have a one-to-one mapping. This means that a NetworkManager property is stored in the keyfile as a variable of the same name and in the same format. However, there are exceptions, mainly to make the keyfile syntax easier to read. For a list of these exceptions, see the nm-settings-keyfile(5)
man page.
For security reasons, because connection profiles can contain sensitive information, such as private keys and passphrases, NetworkManager uses only configuration files owned by the root
user and that are only readable and writable by root
.
Depending on the purpose of the connection profile, save it in one of the following directories:
-
/etc/NetworkManager/system-connections/
: The location of persistent profiles. If you modify a persistent profile by using the NetworkManager API, NetworkManager writes and overwrites files in this directory. -
/run/NetworkManager/system-connections/
: For temporary profiles that are automatically removed when you reboot the system. -
/usr/lib/NetworkManager/system-connections/
: For pre-deployed immutable profiles. When you edit such a profile using the NetworkManager API, NetworkManager copies this profile to either the persistent or temporary storage.
NetworkManager does not automatically reload profiles from disk. When you create or update a connection profile in keyfile format, use the nmcli connection reload
command to inform NetworkManager about the changes.
37.2. Using nmcli
to create keyfile connection profiles in offline mode
Use NetworkManager utilities, such as nmcli
, the network
RHEL system role, or the nmstate
API to manage NetworkManager connections, to create and update configuration files. However, you can also create various connection profiles in the keyfile format in offline mode using the nmcli --offline connection add
command.
The offline mode ensures that nmcli
operates without the NetworkManager
service to produce keyfile connection profiles through standard output. This feature can be useful if:
- You want to create your connection profiles that need to be pre-deployed somewhere. For example in a container image, or as an RPM package.
-
You want to create your connection profiles in an environment where the
NetworkManager
service is not available. For example when you want to use thechroot
utility. Alternatively, when you want to create or modify the network configuration of the RHEL system to be installed through the Kickstart%post
script.
You can create the following connection profile types:
- static Ethernet connection
- dynamic Ethernet connection
- network bond
- network bridge
- VLAN or any kind of supported connections
Procedure
Create a new connection profile in the keyfile format. For example, for a connection profile of an Ethernet device that does not use DHCP, run a similar
nmcli
command:# nmcli --offline connection add type ethernet con-name Example-Connection ipv4.addresses 192.0.2.1/24 ipv4.dns 192.0.2.200 ipv4.method manual > /etc/NetworkManager/system-connections/output.nmconnection
NoteThe connection name you specified with the
con-name
key is saved into theid
variable of the generated profile. When you use thenmcli
command to manage this connection later, specify the connection as follows:-
When the
id
variable is not omitted, use the connection name, for exampleExample-Connection
. -
When the
id
variable is omitted, use the file name without the.nmconnection
suffix, for exampleoutput
.
-
When the
Set permissions to the configuration file so that only the
root
user can read and update it:# chmod 600 /etc/NetworkManager/system-connections/output.nmconnection # chown root:root /etc/NetworkManager/system-connections/output.nmconnection
Start the
NetworkManager
service:# systemctl start NetworkManager.service
If you set the
autoconnect
variable in the profile tofalse
, activate the connection:# nmcli connection up Example-Connection
Verification
Verify that the
NetworkManager
service is running:# systemctl status NetworkManager.service ● NetworkManager.service - Network Manager Loaded: loaded (/usr/lib/systemd/system/NetworkManager.service; enabled; vendor preset: enabled) Active: active (running) since Wed 2022-08-03 13:08:32 CEST; 1min 40s ago ...
Verify that NetworkManager can read the profile from the configuration file:
# nmcli -f TYPE,FILENAME,NAME connection TYPE FILENAME NAME ethernet /etc/NetworkManager/system-connections/output.nmconnection Example-Connection ethernet /etc/sysconfig/network-scripts/ifcfg-enp1s0 enp1s0 ...
If the output does not show the newly created connection, verify that the keyfile permissions and the syntax you used are correct.
Display the connection profile:
# nmcli connection show Example-Connection connection.id: Example-Connection connection.uuid: 232290ce-5225-422a-9228-cb83b22056b4 connection.stable-id: -- connection.type: 802-3-ethernet connection.interface-name: -- connection.autoconnect: yes ...
Additional resources
37.3. Manually creating a NetworkManager profile in keyfile format
You can manually create a NetworkManager connection profile in keyfile format.
Manually creating or updating the configuration files can result in an unexpected or non-functional network configuration. As an alternative, you can use nmcli
in offline mode. See Using nmcli to create keyfile connection profiles in offline mode
Procedure
If you create a profile for a hardware interface, such as Ethernet, display the MAC address of this interface:
# ip address show enp1s0 2: enp1s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000 link/ether 00:53:00:8f:fa:66 brd ff:ff:ff:ff:ff:ff
Create a connection profile. For example, for a connection profile of an Ethernet device that uses DHCP, create the
/etc/NetworkManager/system-connections/example.nmconnection
file with the following content:[connection] id=example_connection type=ethernet autoconnect=true [ipv4] method=auto [ipv6] method=auto [ethernet] mac-address=00:53:00:8f:fa:66
NoteYou can use any file name with a
.nmconnection
suffix. However, when you later usenmcli
commands to manage the connection, you must use the connection name set in theid
variable when you refer to this connection. When you omit theid
variable, use the file name without the.nmconnection
to refer to this connection.Set permissions on the configuration file so that only the
root
user can read and update it:# chown root:root /etc/NetworkManager/system-connections/example.nmconnection # chmod 600 /etc/NetworkManager/system-connections/example.nmconnection
Reload the connection profiles:
# nmcli connection reload
Verify that NetworkManager read the profile from the configuration file:
# nmcli -f NAME,UUID,FILENAME connection NAME UUID FILENAME example-connection 86da2486-068d-4d05-9ac7-957ec118afba /etc/NetworkManager/system-connections/example.nmconnection ...
If the command does not show the newly added connection, verify that the file permissions and the syntax you used in the file are correct.
If you set the
autoconnect
variable in the profile tofalse
, activate the connection:# nmcli connection up example_connection
Verification
Display the connection profile:
# nmcli connection show example_connection
Additional resources
-
nm-settings-keyfile (5)
37.4. The differences in interface renaming with profiles in ifcfg and keyfile format
You can define custom network interface names, such as provider
or lan
to make interface names more descriptive. In this case, the udev
service renames the interfaces. The renaming process works differently depending on whether you use connection profiles in ifcfg
or keyfile format.
- The interface renaming process when using a profile in
ifcfg
format -
The
/usr/lib/udev/rules.d/60-net.rules
udev
rule calls the/lib/udev/rename_device
helper utility. -
The helper utility searches for the
HWADDR
parameter in/etc/sysconfig/network-scripts/ifcfg-*
files. -
If the value set in the variable matches the MAC address of an interface, the helper utility renames the interface to the name set in the
DEVICE
parameter of the file.
-
The
- The interface renaming process when using a profile in keyfile format
- Create a systemd link file or a udev rule to rename an interface.
-
Use the custom interface name in the
interface-name
property of a NetworkManager connection profile.
37.5. Migrating NetworkManager profiles from ifcfg to keyfile format
If you use connection profiles in ifcfg
format, you can convert them to the keyfile format to have all profiles in the preferred format and in one location.
If an ifcfg
file contains the NM_CONTROLLED=no
setting, NetworkManager does not control this profile and, consequently the migration process ignores it.
Prerequisites
-
You have connection profiles in
ifcfg
format in the/etc/sysconfig/network-scripts/
directory. -
If the connection profiles contain a
DEVICE
variable that is set to a custom device name, such asprovider
orlan
, you created a systemd link file or a udev rule for each of the custom device names.
Procedure
Migrate the connection profiles:
# nmcli connection migrate Connection 'enp1s0' (43ed18ab-f0c4-4934-af3d-2b3333948e45) successfully migrated. Connection 'enp2s0' (883333e8-1b87-4947-8ceb-1f8812a80a9b) successfully migrated. ...
Verification
Optionally, you can verify that you successfully migrated all your connection profiles:
# nmcli -f TYPE,FILENAME,NAME connection TYPE FILENAME NAME ethernet /etc/NetworkManager/system-connections/enp1s0.nmconnection enp1s0 ethernet /etc/NetworkManager/system-connections/enp2s0.nmconnection enp2s0 ...
Additional resources
-
nm-settings-keyfile(5)
-
nm-settings-ifcfg-rh(5)
- How the udev device manager renames network interfaces
Chapter 38. Systemd network targets and services
NetworkManager configures the network during the system boot process. However, when booting with a remote root (/), such as if the root directory is stored on an iSCSI device, the network settings are applied in the initial RAM disk (initrd
) before RHEL is started. For example, if the network configuration is specified on the kernel command line using rd.neednet=1
or a configuration is specified to mount remote file systems, then the network settings are applied on initrd
.
RHEL uses the network
and network-online
targets and the NetworkManager-wait-online
service while applying network settings. Also, you can configure systemd
services to start after the network is fully available if these services cannot dynamically reload.
38.1. Differences between the network and network-online systemd target
Systemd maintains the network
and network-online
target units. The special units such as NetworkManager-wait-online.service
, have WantedBy=network-online.target
and Before=network-online.target
parameters. If enabled, these units get started with network-online.target
and delay the target to be reached until some form of network connectivity is established. They delay the network-online
target until the network is connected.
The network-online
target starts a service, which adds substantial delays to further execution. Systemd automatically adds dependencies with Wants
and After
parameters for this target unit to all the System V (SysV) init
script service units with a Linux Standard Base (LSB) header referring to the $network
facility. The LSB header is metadata for init
scripts. You can use it to specify dependencies. This is similar to the systemd
target.
The network
target does not significantly delay the execution of the boot process. Reaching the network
target means that the service that is responsible for setting up the network has started. However, it does not mean that a network device was configured. This target is important during the shutdown of the system. For example, if you have a service that was ordered after the network
target during bootup, then this dependency is reversed during the shutdown. The network does not get disconnected until your service has been stopped. All mount units for remote network file systems automatically start the network-online
target unit and order themselves after it.
The network-online
target unit is only useful during the system starts. After the system has completed booting up, this target does not track the online state of the network. Therefore, you cannot use network-online
to monitor the network connection. This target provides a one-time system startup concept.
38.2. Overview of NetworkManager-wait-online
The synchronous legacy network scripts iterate through all configuration files to set up devices. They apply all network-related configurations and ensure that the network is online.
The NetworkManager-wait-online
service waits with a timeout for the network to be configured. This network configuration involves plugging-in an Ethernet device, scanning for a Wi-Fi device, and so forth. NetworkManager automatically activates suitable profiles that are configured to start automatically. The failure of the automatic activation process due to a DHCP timeout or similar event might keep NetworkManager busy for an extended period of time. Depending on the configuration, NetworkManager retries activating the same profile or a different profile.
When the startup completes, either all profiles are in a disconnected state or are successfully activated. You can configure profiles to auto-connect. The following are a few examples of parameters that set timeouts or define when the connection is considered active:
-
connection.wait-device-timeout
- sets the timeout for the driver to detect the device -
ipv4.may-fail
andipv6.may-fail
- sets activation with one IP address family ready, or whether a particular address family must have completed configuration. -
ipv4.gateway-ping-timeout
- delays activation.
Additional resources
-
nm-settings(5)
man page
38.3. Configuring a systemd service to start after the network has been started
Red Hat Enterprise Linux installs systemd
service files in the /usr/lib/systemd/system/
directory. This procedure creates a drop-in snippet for a service file in /etc/systemd/system/service_name.service.d/
that is used together with the service file in /usr/lib/systemd/system/
to start a particular service after the network is online. It has a higher priority if settings in the drop-in snippet overlap with the ones in the service file in /usr/lib/systemd/system/
.
Procedure
To open the service file in the editor, enter:
# systemctl edit service_name
Enter the following, and save the changes:
[Unit] After=network-online.target
Reload the
systemd
service.# systemctl daemon-reload
Chapter 39. Introduction to Nmstate
Nmstate is a declarative network manager API. The nmstate
package provides the libnmstate
Python library and a command-line utility, nmstatectl
, to manage NetworkManager on RHEL. When you use Nmstate, you describe the expected networking state using YAML or JSON-formatted instructions.
Nmstate has many benefits. For example, it:
- Provides a stable and extensible interface to manage RHEL network capabilities
- Supports atomic and transactional operations at the host and cluster level
- Supports partial editing of most properties and preserves existing settings that are not specified in the instructions
- Provides plug-in support to enable administrators to use their own plug-ins
39.1. Using the libnmstate library in a Python application
The libnmstate
Python library enables developers to use Nmstate in their own application
To use the library, import it in your source code:
import libnmstate
Note that you must install the nmstate
package to use this library.
Example 39.1. Querying the network state using the libnmstate library
The following Python code imports the libnmstate
library and displays the available network interfaces and their state:
import json import libnmstate from libnmstate.schema import Interface net_state = libnmstate.show() for iface_state in net_state[Interface.KEY]: print(iface_state[Interface.NAME] + ": " + iface_state[Interface.STATE])
39.2. Updating the current network configuration using nmstatectl
You can use the nmstatectl
utility to store the current network configuration of one or all interfaces in a file. You can then use this file to:
- Modify the configuration and apply it to the same system.
- Copy the file to a different host and configure the host with the same or modified settings.
For example, you can export the settings of the enp1s0
interface to a file, modify the configuration, and apply the settings to the host.
Prerequisites
-
The
nmstate
package is installed.
Procedure
Export the settings of the
enp1s0
interface to the~/network-config.yml
file:# nmstatectl show enp1s0 > ~/network-config.yml
This command stores the configuration of
enp1s0
in YAML format. To store the output in JSON format, pass the--json
option to the command.If you do not specify an interface name,
nmstatectl
exports the configuration of all interfaces.-
Modify the
~/network-config.yml
file using a text editor to update the configuration. Apply the settings from the
~/network-config.yml
file:# nmstatectl apply ~/network-config.yml
If you exported the settings in JSON format, pass the
--json
option to the command.
39.3. Network states for the network
RHEL system role
The network
RHEL system role supports state configurations in playbooks to configure the devices. For this, use the network_state
variable followed by the state configurations.
Benefits of using the network_state
variable in a playbook:
- Using the declarative method with the state configurations, you can configure interfaces, and the NetworkManager creates a profile for these interfaces in the background.
-
With the
network_state
variable, you can specify the options that you require to change, and all the other options will remain the same as they are. However, with thenetwork_connections
variable, you must specify all settings to change the network connection profile.
For example, to create an Ethernet connection with dynamic IP address settings, use the following vars
block in your playbook:
Playbook with state configurations | Regular playbook |
vars: network_state: interfaces: - name: enp7s0 type: ethernet state: up ipv4: enabled: true auto-dns: true auto-gateway: true auto-routes: true dhcp: true ipv6: enabled: true auto-dns: true auto-gateway: true auto-routes: true autoconf: true dhcp: true |
vars: network_connections: - name: enp7s0 interface_name: enp7s0 type: ethernet autoconnect: yes ip: dhcp4: yes auto6: yes state: up |
For example, to only change the connection status of dynamic IP address settings that you created as above, use the following vars
block in your playbook:
Playbook with state configurations | Regular playbook |
vars: network_state: interfaces: - name: enp7s0 type: ethernet state: down |
vars: network_connections: - name: enp7s0 interface_name: enp7s0 type: ethernet autoconnect: yes ip: dhcp4: yes auto6: yes state: down |
Additional resources
-
/usr/share/ansible/roles/rhel-system-roles.network/README.md
file -
/usr/share/doc/rhel-system-roles/network/
directory
39.4. Additional resources
-
/usr/share/doc/nmstate/README.md
-
/usr/share/doc/nmstate/examples/
Chapter 40. Using and configuring firewalld
A firewall is a way to protect machines from any unwanted traffic from outside. It enables users to control incoming network traffic on host machines by defining a set of firewall rules. These rules are used to sort the incoming traffic and either block it or allow through.
firewalld
is a firewall service daemon that provides a dynamic customizable host-based firewall with a D-Bus interface. Being dynamic, it enables creating, changing, and deleting the rules without the necessity to restart the firewall daemon each time the rules are changed.
firewalld
uses the concepts of zones and services, that simplify the traffic management. Zones are predefined sets of rules. Network interfaces and sources can be assigned to a zone. The traffic allowed depends on the network your computer is connected to and the security level this network is assigned. Firewall services are predefined rules that cover all necessary settings to allow incoming traffic for a specific service and they apply within a zone.
Services use one or more ports or addresses for network communication. Firewalls filter communication based on ports. To allow network traffic for a service, its ports must be open. firewalld
blocks all traffic on ports that are not explicitly set as open. Some zones, such as trusted, allow all traffic by default.
Note that firewalld
with nftables
backend does not support passing custom nftables
rules to firewalld
, using the --direct
option.
40.1. When to use firewalld, nftables, or iptables
The following is a brief overview in which scenario you should use one of the following utilities:
-
firewalld
: Use thefirewalld
utility for simple firewall use cases. The utility is easy to use and covers the typical use cases for these scenarios. -
nftables
: Use thenftables
utility to set up complex and performance-critical firewalls, such as for a whole network. -
iptables
: Theiptables
utility on Red Hat Enterprise Linux uses thenf_tables
kernel API instead of thelegacy
back end. Thenf_tables
API provides backward compatibility so that scripts that useiptables
commands still work on Red Hat Enterprise Linux. For new firewall scripts, Red Hat recommends to usenftables
.
To prevent the different firewall-related services (firewalld
, nftables
, or iptables
) from influencing each other, run only one of them on a RHEL host, and disable the other services.
40.2. Firewall zones
You can use the firewalld
utility to separate networks into different zones according to the level of trust that you have with the interfaces and traffic within that network. A connection can only be part of one zone, but you can use that zone for many network connections.
firewalld
follows strict principles in regards to zones:
- Traffic ingresses only one zone.
- Traffic egresses only one zone.
- A zone defines a level of trust.
- Intrazone traffic (within the same zone) is allowed by default.
- Interzone traffic (from zone to zone) is denied by default.
Principles 4 and 5 are a consequence of principle 3.
Principle 4 is configurable through the zone option --remove-forward
. Principle 5 is configurable by adding new policies.
NetworkManager
notifies firewalld
of the zone of an interface. You can assign zones to interfaces with the following utilities:
-
NetworkManager
-
firewall-config
utility -
firewall-cmd
utility - The RHEL web console
The RHEL web console, firewall-config
, and firewall-cmd
can only edit the appropriate NetworkManager
configuration files. If you change the zone of the interface using the web console, firewall-cmd
, or firewall-config
, the request is forwarded to NetworkManager
and is not handled by firewalld
.
The /usr/lib/firewalld/zones/
directory stores the predefined zones, and you can instantly apply them to any available network interface. These files are copied to the /etc/firewalld/zones/
directory only after they are modified. The default settings of the predefined zones are as follows:
block
-
Suitable for: Any incoming network connections are rejected with an icmp-host-prohibited message for
IPv4
and icmp6-adm-prohibited forIPv6
. - Accepts: Only network connections initiated from within the system.
-
Suitable for: Any incoming network connections are rejected with an icmp-host-prohibited message for
dmz
- Suitable for: Computers in your DMZ that are publicly-accessible with limited access to your internal network.
- Accepts: Only selected incoming connections.
drop
Suitable for: Any incoming network packets are dropped without any notification.
- Accepts: Only outgoing network connections.
external
- Suitable for: External networks with masquerading enabled, especially for routers. Situations when you do not trust the other computers on the network.
- Accepts: Only selected incoming connections.
home
- Suitable for: Home environment where you mostly trust the other computers on the network.
- Accepts: Only selected incoming connections.
internal
- Suitable for: Internal networks where you mostly trust the other computers on the network.
- Accepts: Only selected incoming connections.
public
- Suitable for: Public areas where you do not trust other computers on the network.
- Accepts: Only selected incoming connections.
trusted
- Accepts: All network connections.
work
Suitable for: Work environment where you mostly trust the other computers on the network.
- Accepts: Only selected incoming connections.
One of these zones is set as the default zone. When interface connections are added to NetworkManager
, they are assigned to the default zone. On installation, the default zone in firewalld
is the public
zone. You can change the default zone.
Make network zone names self-explanatory to help users understand them quickly.
To avoid any security problems, review the default zone configuration and disable any unnecessary services according to your needs and risk assessments.
Additional resources
-
firewalld.zone(5)
man page
40.3. Firewall policies
The firewall policies specify the desired security state of your network. They outline rules and actions to take for different types of traffic. Typically, the policies contain rules for the following types of traffic:
- Incoming traffic
- Outgoing traffic
- Forward traffic
- Specific services and applications
- Network address translations (NAT)
Firewall policies use the concept of firewall zones. Each zone is associated with a specific set of firewall rules that determine the traffic allowed. Policies apply firewall rules in a stateful, unidirectional manner. This means you only consider one direction of the traffic. The traffic return path is implicitly allowed due to stateful filtering of firewalld
.
Policies are associated with an ingress zone and an egress zone. The ingress zone is where the traffic originated (received). The egress zone is where the traffic leaves (sent).
The firewall rules defined in a policy can reference the firewall zones to apply consistent configurations across multiple network interfaces.
40.4. Firewall rules
You can use the firewall rules to implement specific configurations for allowing or blocking network traffic. As a result, you can control the flow of network traffic to protect your system from security threats.
Firewall rules typically define certain criteria based on various attributes. The attributes can be as:
- Source IP addresses
- Destination IP addresses
- Transfer Protocols (TCP, UDP, …)
- Ports
- Network interfaces
The firewalld
utility organizes the firewall rules into zones (such as public
, internal
, and others) and policies. Each zone has its own set of rules that determine the level of traffic freedom for network interfaces associated with a particular zone.
40.5. Zone configuration files
A firewalld
zone configuration file contains the information for a zone. These are the zone description, services, ports, protocols, icmp-blocks, masquerade, forward-ports and rich language rules in an XML file format. The file name has to be zone-name.xml
where the length of zone-name is currently limited to 17 chars. The zone configuration files are located in the /usr/lib/firewalld/zones/
and /etc/firewalld/zones/
directories.
The following example shows a configuration that allows one service (SSH
) and one port range, for both the TCP
and UDP
protocols:
<?xml version="1.0" encoding="utf-8"?> <zone> <short>My Zone</short> <description>Here you can describe the characteristic features of the zone.</description> <service name="ssh"/> <port protocol="udp" port="1025-65535"/> <port protocol="tcp" port="1025-65535"/> </zone>
Additional resources
-
firewalld.zone
manual page
40.6. Predefined firewalld services
The firewalld
service is a predefined set of firewall rules that define access to a specific application or network service. Each service represents a combination of the following elements:
- Local port
- Network protocol
- Associated firewall rules
- Source ports and destinations
- Firewall helper modules that load automatically if a service is enabled
A service simplifies packet filtering and saves you time because it achieves several tasks at once. For example, firewalld
can perform the following tasks at once:
- Open a port
- Define network protocol
- Enable packet forwarding
Service configuration options and generic file information are described in the firewalld.service(5)
man page. The services are specified by means of individual XML configuration files, which are named in the following format: service-name.xml
. Protocol names are preferred over service or application names in firewalld
.
You can configure firewalld
in the following ways:
Use utilities:
-
firewall-config
- graphical utility -
firewall-cmd
- command-line utility -
firewall-offline-cmd
- command-line utility
-
Edit the XML files in the
/etc/firewalld/services/
directory.If you do not add or change the service, no corresponding XML file exists in
/etc/firewalld/services/
. You can use the files in/usr/lib/firewalld/services/
as templates.
Additional resources
-
The
firewalld.service(5)
man page
40.7. Working with firewalld zones
Zones represent a concept to manage incoming traffic more transparently. The zones are connected to networking interfaces or assigned a range of source addresses. You manage firewall rules for each zone independently, which enables you to define complex firewall settings and apply them to the traffic.
40.7.1. Customizing firewall settings for a specific zone to enhance security
You can strengthen your network security by modifying the firewall settings and associating a specific network interface or connection with a particular firewall zone. By defining granular rules and restrictions for a zone, you can control inbound and outbound traffic based on your intended security levels.
For example, you can achieve the following benefits:
- Protection of sensitive data
- Prevention of unauthorized access
- Mitigation of potential network threats
Prerequisites
-
The
firewalld
service is running.
Procedure
List the available firewall zones:
# firewall-cmd --get-zones
The
firewall-cmd --get-zones
command displays all zones that are available on the system, but it does not show any details for particular zones. To see more detailed information for all zones, use thefirewall-cmd --list-all-zones
command.- Choose the zone you want to use for this configuration.
Modify firewall settings for the chosen zone. For example, to allow the
SSH
service and remove theftp
service:# firewall-cmd --add-service=ssh --zone=<your_chosen_zone> # firewall-cmd --remove-service=ftp --zone=<same_chosen_zone>
Assign a network interface to the firewall zone:
List the available network interfaces:
# firewall-cmd --get-active-zones
Activity of a zone is determined by the presence of network interfaces or source address ranges that match its configuration. The default zone is active for unclassified traffic but is not always active if no traffic matches its rules.
Assign a network interface to the chosen zone:
# firewall-cmd --zone=<your_chosen_zone> --change-interface=<interface_name> --permanent
Assigning a network interface to a zone is more suitable for applying consistent firewall settings to all traffic on a particular interface (physical or virtual).
The
firewall-cmd
command, when used with the--permanent
option, often involves updating NetworkManager connection profiles to make changes to the firewall configuration permanent. This integration betweenfirewalld
and NetworkManager ensures consistent network and firewall settings.
Verification
Display the updated settings for your chosen zone:
# firewall-cmd --zone=<your_chosen_zone> --list-all
The command output displays all zone settings including the assigned services, network interface, and network connections (sources).
40.7.2. Changing the default zone
System administrators assign a zone to a networking interface in its configuration files. If an interface is not assigned to a specific zone, it is assigned to the default zone. After each restart of the firewalld
service, firewalld
loads the settings for the default zone and makes it active. Note that settings for all other zones are preserved and ready to be used.
Typically, zones are assigned to interfaces by NetworkManager according to the connection.zone
setting in NetworkManager connection profiles. Also, after a reboot NetworkManager manages assignments for "activating" those zones.
Prerequisites
-
The
firewalld
service is running.
Procedure
To set up the default zone:
Display the current default zone:
# firewall-cmd --get-default-zone
Set the new default zone:
# firewall-cmd --set-default-zone <zone_name>
NoteFollowing this procedure, the setting is a permanent setting, even without the
--permanent
option.
40.7.3. Assigning a network interface to a zone
It is possible to define different sets of rules for different zones and then change the settings quickly by changing the zone for the interface that is being used. With multiple interfaces, a specific zone can be set for each of them to distinguish traffic that is coming through them.
Procedure
To assign the zone to a specific interface:
List the active zones and the interfaces assigned to them:
# firewall-cmd --get-active-zones
Assign the interface to a different zone:
# firewall-cmd --zone=zone_name --change-interface=interface_name --permanent
40.7.4. Assigning a zone to a connection using nmcli
You can add a firewalld
zone to a NetworkManager
connection using the nmcli
utility.
Procedure
Assign the zone to the
NetworkManager
connection profile:# nmcli connection modify profile connection.zone zone_name
Activate the connection:
# nmcli connection up profile
40.7.5. Manually assigning a zone to a network connection in a connection profile file
If you cannot use the nmcli
utility to modify a connection profile, you can manually edit the corresponding file of the profile to assign a firewalld
zone.
Modifying the connection profile with the nmcli
utility to assign a firewalld
zone is more efficient. For details, see Assigning a network interface to a zone.
Procedure
Determine the path to the connection profile and its format:
# nmcli -f NAME,FILENAME connection NAME FILENAME enp1s0 /etc/NetworkManager/system-connections/enp1s0.nmconnection enp7s0 /etc/sysconfig/network-scripts/ifcfg-enp7s0
NetworkManager uses separate directories and file names for the different connection profile formats:
-
Profiles in
/etc/NetworkManager/system-connections/<connection_name>.nmconnection
files use the keyfile format. -
Profiles in
/etc/sysconfig/network-scripts/ifcfg-<interface_name>
files use the ifcfg format.
-
Profiles in
Depending on the format, update the corresponding file:
If the file uses the keyfile format, append
zone=<name>
to the[connection]
section of the/etc/NetworkManager/system-connections/<connection_name>.nmconnection
file:[connection] ... zone=internal
If the file uses the ifcfg format, append
ZONE=<name>
to the/etc/sysconfig/network-scripts/ifcfg-<interface_name>
file:ZONE=internal
Reload the connection profiles:
# nmcli connection reload
Reactivate the connection profiles
# nmcli connection up <profile_name>
Verification
Display the zone of the interface, for example:
# firewall-cmd --get-zone-of-interface enp1s0 internal
40.7.6. Manually assigning a zone to a network connection in an ifcfg file
When the connection is managed by NetworkManager, it must be aware of a zone that it uses. For every network connection profile, a zone can be specified, which provides the flexibility of various firewall settings according to the location of the computer with portable devices. Thus, zones and settings can be specified for different locations, such as company or home.
Procedure
To set a zone for a connection, edit the
/etc/sysconfig/network-scripts/ifcfg-connection_name
file and add a line that assigns a zone to this connection:ZONE=zone_name
40.7.7. Creating a new zone
To use custom zones, create a new zone and use it just like a predefined zone. New zones require the --permanent
option, otherwise the command does not work.
Prerequisites
-
The
firewalld
service is running.
Procedure
Create a new zone:
# firewall-cmd --permanent --new-zone=zone-name
Make the new zone usable:
# firewall-cmd --reload
The command applies recent changes to the firewall configuration without interrupting network services that are already running.
Verification
Check if the new zone is added to your permanent settings:
# firewall-cmd --get-zones --permanent
40.7.8. Enabling zones by using the web console
You can apply predefined and existing firewall zones on a particular interface or a range of IP addresses through the RHEL web console.
Prerequisites
You have installed the RHEL 8 web console.
For instructions, see Installing and enabling the web console.
Procedure
Log in to the RHEL 8 web console.
For details, see Logging in to the web console.
- Click Networking.
Click on the
button.If you do not see the
button, log in to the web console with the administrator privileges.- In the Firewall section, click Add new zone.
In the Add zone dialog box, select a zone from the Trust level options.
The web console displays all zones predefined in the
firewalld
service.- In the Interfaces part, select an interface or interfaces on which the selected zone is applied.
In the Allowed Addresses part, you can select whether the zone is applied on:
- the whole subnet
or a range of IP addresses in the following format:
- 192.168.1.0
- 192.168.1.0/24
- 192.168.1.0/24, 192.168.1.0
Click on the
button.
Verification
Check the configuration in the Firewall section:
40.7.9. Disabling zones by using the web console
You can disable a firewall zone in your firewall configuration by using the web console.
Prerequisites
You have installed the RHEL 8 web console.
For instructions, see Installing and enabling the web console.
Procedure
Log in to the RHEL 8 web console.
For details, see Logging in to the web console.
- Click Networking.
Click on the
button.If you do not see the
button, log in to the web console with the administrator privileges.Click on the Options icon at the zone you want to remove.
- Click Delete.
The zone is now disabled and the interface does not include opened services and ports which were configured in the zone.
40.7.10. Using zone targets to set default behavior for incoming traffic
For every zone, you can set a default behavior that handles incoming traffic that is not further specified. Such behavior is defined by setting the target of the zone. There are four options:
-
ACCEPT
: Accepts all incoming packets except those disallowed by specific rules. -
REJECT
: Rejects all incoming packets except those allowed by specific rules. Whenfirewalld
rejects packets, the source machine is informed about the rejection. -
DROP
: Drops all incoming packets except those allowed by specific rules. Whenfirewalld
drops packets, the source machine is not informed about the packet drop. -
default
: Similar behavior as forREJECT
, but with special meanings in certain scenarios.
Prerequisites
-
The
firewalld
service is running.
Procedure
To set a target for a zone:
List the information for the specific zone to see the default target:
# firewall-cmd --zone=zone-name --list-all
Set a new target in the zone:
# firewall-cmd --permanent --zone=zone-name --set-target=<default|ACCEPT|REJECT|DROP>
Additional resources
-
firewall-cmd(1)
man page
40.8. Controlling network traffic using firewalld
The firewalld
package installs a large number of predefined service files and you can add more or customize them. You can then use these service definitions to open or close ports for services without knowing the protocol and port numbers they use.
40.8.1. Controlling traffic with predefined services using the CLI
The most straightforward method to control traffic is to add a predefined service to firewalld
. This opens all necessary ports and modifies other settings according to the service definition file.
Prerequisites
-
The
firewalld
service is running.
Procedure
Check that the service in
firewalld
is not already allowed:# firewall-cmd --list-services ssh dhcpv6-client
The command lists the services that are enabled in the default zone.
List all predefined services in
firewalld
:# firewall-cmd --get-services RH-Satellite-6 amanda-client amanda-k5-client bacula bacula-client bitcoin bitcoin-rpc bitcoin-testnet bitcoin-testnet-rpc ceph ceph-mon cfengine condor-collector ctdb dhcp dhcpv6 dhcpv6-client dns docker-registry ...
The command displays a list of available services for the default zone.
Add the service to the list of services that
firewalld
allows:# firewall-cmd --add-service=<service_name>
The command adds the specified service to the default zone.
Make the new settings persistent:
# firewall-cmd --runtime-to-permanent
The command applies these runtime changes to the permanent configuration of the firewall. By default, it applies these changes to the configuration of the default zone.
Verification
List all permanent firewall rules:
# firewall-cmd --list-all --permanent public target: default icmp-block-inversion: no interfaces: sources: services: cockpit dhcpv6-client ssh ports: protocols: forward: no masquerade: no forward-ports: source-ports: icmp-blocks: rich rules:
The command displays complete configuration with the permanent firewall rules of the default firewall zone (
public
).Check the validity of the permanent configuration of the
firewalld
service.# firewall-cmd --check-config success
If the permanent configuration is invalid, the command returns an error with further details:
# firewall-cmd --check-config Error: INVALID_PROTOCOL: 'public.xml': 'tcpx' not from {'tcp'|'udp'|'sctp'|'dccp'}
You can also manually inspect the permanent configuration files to verify the settings. The main configuration file is
/etc/firewalld/firewalld.conf
. The zone-specific configuration files are in the/etc/firewalld/zones/
directory and the policies are in the/etc/firewalld/policies/
directory.
40.8.2. Controlling traffic with predefined services using the GUI
You can control the network traffic with predefined services using a graphical user interface. The Firewall Configuration application provides an accessible and user-friendly alternative to the command-line utilities.
Prerequisites
-
You installed the
firewall-config
package. -
The
firewalld
service is running.
Procedure
To enable or disable a predefined or custom service:
- Start the firewall-config utility and select the network zone whose services are to be configured.
-
Select the
Zones
tab and then theServices
tab below. - Select the checkbox for each type of service you want to trust or clear the checkbox to block a service in the selected zone.
To edit a service:
- Start the firewall-config utility.
-
Select
Permanent
from the menu labeledConfiguration
. Additional icons and menu buttons appear at the bottom of the window. - Select the service you want to configure.
The Ports
, Protocols
, and Source Port
tabs enable adding, changing, and removing of ports, protocols, and source port for the selected service. The modules tab is for configuring Netfilter helper modules. The Destination
tab enables limiting traffic to a particular destination address and Internet Protocol (IPv4
or IPv6
).
It is not possible to alter service settings in the Runtime
mode.
Verification
- Press the Super key to enter the Activities overview.
Select the Firewall Configuration utility.
-
You can also start the graphical firewall configuration utility using the command-line, by entering the
firewall-config
command.
-
You can also start the graphical firewall configuration utility using the command-line, by entering the
View the list of configurations of your firewall:
The Firewall Configuration
window opens. Note that this command can be run as a normal user, but you are prompted for an administrator password occasionally.
40.8.3. Enabling services on the firewall by using the web console
By default, services are added to the default firewall zone. If you use more firewall zones on more network interfaces, you must select a zone first and then add the service with port.
The RHEL 8 web console displays predefined firewalld
services and you can add them to active firewall zones.
The RHEL 8 web console configures the firewalld service.
The web console does not allow generic firewalld
rules which are not listed in the web console.
Prerequisites
You have installed the RHEL 8 web console.
For instructions, see Installing and enabling the web console.
Procedure
Log in to the RHEL 8 web console.
For details, see Logging in to the web console.
- Click Networking.
Click on the
button.If you do not see the
button, log in to the web console with the administrator privileges.In the Firewall section, select a zone for which you want to add the service and click Add Services.
- In the Add Services dialog box, find the service you want to enable on the firewall.
Enable services according to your scenario:
- Click Add Services.
At this point, the RHEL 8 web console displays the service in the zone’s list of Services.
40.8.4. Configuring custom ports by using the web console
You can add configure custom ports for services through the RHEL web console.
Prerequisites
You have installed the RHEL 8 web console.
For instructions, see Installing and enabling the web console.
-
The
firewalld
service is running.
Procedure
Log in to the RHEL 8 web console.
For details, see Logging in to the web console.
- Click Networking.
Click on the
button.If you do not see the
button, log in to the web console with the administrative privileges.In the Firewall section, select a zone for which you want to configure a custom port and click Add Services.
- In the Add services dialog box, click on the radio button.
In the TCP and UDP fields, add ports according to examples. You can add ports in the following formats:
- Port numbers such as 22
- Range of port numbers such as 5900-5910
- Aliases such as nfs, rsync
NoteYou can add multiple values into each field. Values must be separated with the comma and without the space, for example: 8080,8081,http
After adding the port number in the TCP filed, the UDP filed, or both, verify the service name in the Name field.
The Name field displays the name of the service for which is this port reserved. You can rewrite the name if you are sure that this port is free to use and no server needs to communicate on this port.
- In the Name field, add a name for the service including defined ports.
Click on the
button.
To verify the settings, go to the Firewall page and find the service in the list of zone’s Services.
40.8.5. Configuring firewalld to allow hosting a secure web server
Ports are logical services that enable an operating system to receive and distinguish network traffic and forward it to system services. The system services are represented by a daemon that listens on the port and waits for any traffic coming to this port.
Normally, system services listen on standard ports that are reserved for them. The httpd
daemon, for example, listens on port 80. However, system administrators can directly specify the port number instead of the service name.
You can use the firewalld
service to configure access to a secure web server for hosting your data.
Prerequisites
-
The
firewalld
service is running.
Procedure
Check the currently active firewall zone:
# firewall-cmd --get-active-zones
Add the HTTPS service to the appropriate zone:
# firewall-cmd --zone=<zone_name> --add-service=https --permanent
Reload the firewall configuration:
# firewall-cmd --reload
Verification
Check if the port is open in
firewalld
:If you opened the port by specifying the port number, enter:
# firewall-cmd --zone=<zone_name> --list-all
If you opened the port by specifying a service definition, enter:
# firewall-cmd --zone=<zone_name> --list-services
40.8.6. Closing unused or unnecessary ports to enhance network security
When an open port is no longer needed, you can use the firewalld
utility to close it.
Close all unnecessary ports to reduce the potential attack surface and minimize the risk of unauthorized access or exploitation of vulnerabilities.
Procedure
List all allowed ports:
# firewall-cmd --list-ports
By default, this command lists the ports that are enabled in the default zone.
NoteThis command will only give you a list of ports that are opened as ports. You will not be able to see any open ports that are opened as a service. For that case, consider using the
--list-all
option instead of--list-ports
.Remove the port from the list of allowed ports to close it for the incoming traffic:
# firewall-cmd --remove-port=port-number/port-type
This command removes a port from a zone. If you do not specify a zone, it will remove the port from the default zone.
Make the new settings persistent:
# firewall-cmd --runtime-to-permanent
Without specifying a zone, this command applies runtime changes to the permanent configuration of the default zone.
Verification
List the active zones and choose the zone you want to inspect:
# firewall-cmd --get-active-zones
List the currently open ports in the selected zone to check if the unused or unnecessary ports are closed:
# firewall-cmd --zone=<zone_to_inspect> --list-ports
40.8.7. Controlling traffic through the CLI
You can use the firewall-cmd
command to:
- disable networking traffic
- enable networking traffic
As a result, you can for example enhance your system defenses, ensure data privacy or optimize network resources.
Enabling panic mode stops all networking traffic. For this reason, it should be used only when you have the physical access to the machine or if you are logged in using a serial console.
Procedure
To immediately disable networking traffic, switch panic mode on:
# firewall-cmd --panic-on
Switching off panic mode reverts the firewall to its permanent settings. To switch panic mode off, enter:
# firewall-cmd --panic-off
Verification
To see whether panic mode is switched on or off, use:
# firewall-cmd --query-panic
40.8.8. Controlling traffic with protocols using GUI
To permit traffic through the firewall using a certain protocol, you can use the GUI.
Prerequisites
-
You installed the
firewall-config
package
Procedure
- Start the firewall-config tool and select the network zone whose settings you want to change.
-
Select the
Protocols
tab and click theAdd
button on the right-hand side. TheProtocol
window opens. -
Either select a protocol from the list or select the
Other Protocol
check box and enter the protocol in the field.
40.9. Using zones to manage incoming traffic depending on a source
You can use zones to manage incoming traffic based on its source. Incoming traffic in this context is any data that is destined for your system, or passes through the host running firewalld
. The source typically refers to the IP address or network range from which the traffic originates. As a result, you can sort incoming traffic and assign it to different zones to allow or disallow services that can be reached by that traffic.
Matching by source address takes precedence over matching by interface name. When you add a source to a zone, the firewall will prioritize the source-based rules for incoming traffic over interface-based rules. This means that if incoming traffic matches a source address specified for a particular zone, the zone associated with that source address will determine how the traffic is handled, regardless of the interface through which it arrives. On the other hand, interface-based rules are generally a fallback for traffic that does not match specific source-based rules. These rules apply to traffic, for which the source is not explicitly associated with a zone. This allows you to define a default behavior for traffic that does not have a specific source-defined zone.
40.9.1. Adding a source
To route incoming traffic into a specific zone, add the source to that zone. The source can be an IP address or an IP mask in the classless inter-domain routing (CIDR) notation.
In case you add multiple zones with an overlapping network range, they are ordered alphanumerically by zone name and only the first one is considered.
To set the source in the current zone:
# firewall-cmd --add-source=<source>
To set the source IP address for a specific zone:
# firewall-cmd --zone=zone-name --add-source=<source>
The following procedure allows all incoming traffic from 192.168.2.15 in the trusted
zone:
Procedure
List all available zones:
# firewall-cmd --get-zones
Add the source IP to the trusted zone in the permanent mode:
# firewall-cmd --zone=trusted --add-source=192.168.2.15
Make the new settings persistent:
# firewall-cmd --runtime-to-permanent
40.9.2. Removing a source
When you remove a source from a zone, the traffic which originates from the source is no longer directed through the rules specified for that source. Instead, the traffic falls back to the rules and settings of the zone associated with the interface from which it originates, or goes to the default zone.
Procedure
List allowed sources for the required zone:
# firewall-cmd --zone=zone-name --list-sources
Remove the source from the zone permanently:
# firewall-cmd --zone=zone-name --remove-source=<source>
Make the new settings persistent:
# firewall-cmd --runtime-to-permanent
40.9.3. Removing a source port
By removing a source port you disable sorting the traffic based on a port of origin.
Procedure
To remove a source port:
# firewall-cmd --zone=zone-name --remove-source-port=<port-name>/<tcp|udp|sctp|dccp>
40.9.4. Using zones and sources to allow a service for only a specific domain
To allow traffic from a specific network to use a service on a machine, use zones and source. The following procedure allows only HTTP traffic from the 192.0.2.0/24
network while any other traffic is blocked.
When you configure this scenario, use a zone that has the default
target. Using a zone that has the target set to ACCEPT
is a security risk, because for traffic from 192.0.2.0/24
, all network connections would be accepted.
Procedure
List all available zones:
# firewall-cmd --get-zones block dmz drop external home internal public trusted work
Add the IP range to the
internal
zone to route the traffic originating from the source through the zone:# firewall-cmd --zone=internal --add-source=192.0.2.0/24
Add the
http
service to theinternal
zone:# firewall-cmd --zone=internal --add-service=http
Make the new settings persistent:
# firewall-cmd --runtime-to-permanent
Verification
Check that the
internal
zone is active and that the service is allowed in it:# firewall-cmd --zone=internal --list-all internal (active) target: default icmp-block-inversion: no interfaces: sources: 192.0.2.0/24 services: cockpit dhcpv6-client mdns samba-client ssh http ...
Additional resources
-
firewalld.zones(5)
man page
40.10. Filtering forwarded traffic between zones
firewalld
enables you to control the flow of network data between different firewalld
zones. By defining rules and policies, you can manage how traffic is allowed or blocked when it moves between these zones.
The policy objects feature provides forward and output filtering in firewalld
. You can use firewalld
to filter traffic between different zones to allow access to locally hosted VMs to connect the host.
40.10.1. The relationship between policy objects and zones
Policy objects allow the user to attach firewalld’s primitives such as services, ports, and rich rules to the policy. You can apply the policy objects to traffic that passes between zones in a stateful and unidirectional manner.
# firewall-cmd --permanent --new-policy myOutputPolicy # firewall-cmd --permanent --policy myOutputPolicy --add-ingress-zone HOST # firewall-cmd --permanent --policy myOutputPolicy --add-egress-zone ANY
HOST
and ANY
are the symbolic zones used in the ingress and egress zone lists.
-
The
HOST
symbolic zone allows policies for the traffic originating from or has a destination to the host running firewalld. -
The
ANY
symbolic zone applies policy to all the current and future zones.ANY
symbolic zone acts as a wildcard for all zones.
40.10.2. Using priorities to sort policies
Multiple policies can apply to the same set of traffic, therefore, priorities should be used to create an order of precedence for the policies that may be applied.
To set a priority to sort the policies:
# firewall-cmd --permanent --policy mypolicy --set-priority -500
In the above example -500 is a lower priority value but has higher precedence. Thus, -500 will execute before -100.
Lower numerical priority values have higher precedence and are applied first.
40.10.3. Using policy objects to filter traffic between locally hosted containers and a network physically connected to the host
The policy objects feature allows users to filter traffic between Podman and firewalld zones.
Red Hat recommends blocking all traffic by default and opening the selective services needed for the Podman utility.
Procedure
Create a new firewall policy:
# firewall-cmd --permanent --new-policy podmanToAny
Block all traffic from Podman to other zones and allow only necessary services on Podman:
# firewall-cmd --permanent --policy podmanToAny --set-target REJECT # firewall-cmd --permanent --policy podmanToAny --add-service dhcp # firewall-cmd --permanent --policy podmanToAny --add-service dns # firewall-cmd --permanent --policy podmanToAny --add-service https
Create a new Podman zone:
# firewall-cmd --permanent --new-zone=podman
Define the ingress zone for the policy:
# firewall-cmd --permanent --policy podmanToHost --add-ingress-zone podman
Define the egress zone for all other zones:
# firewall-cmd --permanent --policy podmanToHost --add-egress-zone ANY
Setting the egress zone to ANY means that you filter from Podman to other zones. If you want to filter to the host, then set the egress zone to HOST.
Restart the firewalld service:
# systemctl restart firewalld
Verification
Verify the Podman firewall policy to other zones:
# firewall-cmd --info-policy podmanToAny podmanToAny (active) ... target: REJECT ingress-zones: podman egress-zones: ANY services: dhcp dns https ...
40.10.4. Setting the default target of policy objects
You can specify --set-target options for policies. The following targets are available:
-
ACCEPT
- accepts the packet -
DROP
- drops the unwanted packets -
REJECT
- rejects unwanted packets with an ICMP reply CONTINUE
(default) - packets will be subject to rules in following policies and zones.# firewall-cmd --permanent --policy mypolicy --set-target CONTINUE
Verification
Verify information about the policy
# firewall-cmd --info-policy mypolicy
40.10.5. Using DNAT to forward HTTPS traffic to a different host
If your web server runs in a DMZ with private IP addresses, you can configure destination network address translation (DNAT) to enable clients on the internet to connect to this web server. In this case, the host name of the web server resolves to the public IP address of the router. When a client establishes a connection to a defined port on the router, the router forwards the packets to the internal web server.
Prerequisites
- The DNS server resolves the host name of the web server to the router’s IP address.
You know the following settings:
- The private IP address and port number that you want to forward
- The IP protocol to be used
- The destination IP address and port of the web server where you want to redirect the packets
Procedure
Create a firewall policy:
# firewall-cmd --permanent --new-policy <example_policy>
The policies, as opposed to zones, allow packet filtering for input, output, and forwarded traffic. This is important, because forwarding traffic to endpoints on locally run web servers, containers, or virtual machines requires such capability.
Configure symbolic zones for the ingress and egress traffic to also enable the router itself to connect to its local IP address and forward this traffic:
# firewall-cmd --permanent --policy=<example_policy> --add-ingress-zone=HOST # firewall-cmd --permanent --policy=<example_policy> --add-egress-zone=ANY
The
--add-ingress-zone=HOST
option refers to packets generated locally and transmitted out of the local host. The--add-egress-zone=ANY
option refers to traffic moving to any zone.Add a rich rule that forwards traffic to the web server:
# firewall-cmd --permanent --policy=<example_policy> --add-rich-rule='rule family="ipv4" destination address="192.0.2.1" forward-port port="443" protocol="tcp" to-port="443" to-addr="192.51.100.20"'
The rich rule forwards TCP traffic from port 443 on the IP address of the router (192.0.2.1) to port 443 of the IP address of the web server (192.51.100.20).
Reload the firewall configuration files:
# firewall-cmd --reload success
Activate routing of 127.0.0.0/8 in the kernel:
For persistent changes, run:
# echo "net.ipv4.conf.all.route_localnet=1" > /etc/sysctl.d/90-enable-route-localnet.conf
The command persistently configures the
route_localnet
kernel parameter and ensures that the setting is preserved after the system reboots.For applying the settings immediately without a system reboot, run:
# sysctl -p /etc/sysctl.d/90-enable-route-localnet.conf
The
sysctl
command is useful for applying on-the-fly changes, however the configuration will not persist across system reboots.
Verification
Connect to the IP address of the router and to the port that you have forwarded to the web server:
# curl https://192.0.2.1:443
Optional: Verify that the
net.ipv4.conf.all.route_localnet
kernel parameter is active:# sysctl net.ipv4.conf.all.route_localnet net.ipv4.conf.all.route_localnet = 1
Verify that
<example_policy>
is active and contains the settings you need, especially the source IP address and port, protocol to be used, and the destination IP address and port:# firewall-cmd --info-policy=<example_policy> example_policy (active) priority: -1 target: CONTINUE ingress-zones: HOST egress-zones: ANY services: ports: protocols: masquerade: no forward-ports: source-ports: icmp-blocks: rich rules: rule family="ipv4" destination address="192.0.2.1" forward-port port="443" protocol="tcp" to-port="443" to-addr="192.51.100.20"
Additional resources
-
firewall-cmd(1)
,firewalld.policies(5)
,firewalld.richlanguage(5)
,sysctl(8)
, andsysctl.conf(5)
man pages - Using configuration files in /etc/sysctl.d/ to adjust kernel parameters
40.11. Configuring NAT using firewalld
With firewalld
, you can configure the following network address translation (NAT) types:
- Masquerading
- Destination NAT (DNAT)
- Redirect
40.11.1. Network address translation types
These are the different network address translation (NAT) types:
- Masquerading
Use one of these NAT types to change the source IP address of packets. For example, Internet Service Providers (ISPs) do not route private IP ranges, such as
10.0.0.0/8
. If you use private IP ranges in your network and users should be able to reach servers on the internet, map the source IP address of packets from these ranges to a public IP address.Masquerading automatically uses the IP address of the outgoing interface. Therefore, use masquerading if the outgoing interface uses a dynamic IP address.
- Destination NAT (DNAT)
- Use this NAT type to rewrite the destination address and port of incoming packets. For example, if your web server uses an IP address from a private IP range and is, therefore, not directly accessible from the internet, you can set a DNAT rule on the router to redirect incoming traffic to this server.
- Redirect
- This type is a special case of DNAT that redirects packets to a different port on the local machine. For example, if a service runs on a different port than its standard port, you can redirect incoming traffic from the standard port to this specific port.
40.11.2. Configuring IP address masquerading
You can enable IP masquerading on your system. IP masquerading hides individual machines behind a gateway when accessing the internet.
Procedure
To check if IP masquerading is enabled (for example, for the
external
zone), enter the following command asroot
:# firewall-cmd --zone=external --query-masquerade
The command prints
yes
with exit status0
if enabled. It printsno
with exit status1
otherwise. Ifzone
is omitted, the default zone will be used.To enable IP masquerading, enter the following command as
root
:# firewall-cmd --zone=external --add-masquerade
-
To make this setting persistent, pass the
--permanent
option to the command. To disable IP masquerading, enter the following command as
root
:# firewall-cmd --zone=external --remove-masquerade
To make this setting permanent, pass the
--permanent
option to the command.
40.11.3. Using DNAT to forward incoming HTTP traffic
You can use destination network address translation (DNAT) to direct incoming traffic from one destination address and port to another. Typically, this is useful for redirecting incoming requests from an external network interface to specific internal servers or services.
Prerequisites
-
The
firewalld
service is running.
Procedure
Create the
/etc/sysctl.d/90-enable-IP-forwarding.conf
file with the following content:net.ipv4.ip_forward=1
This setting enables IP forwarding in the kernel. It makes the internal RHEL server act as a router and forward packets from network to network.
Load the setting from the
/etc/sysctl.d/90-enable-IP-forwarding.conf
file:# sysctl -p /etc/sysctl.d/90-enable-IP-forwarding.conf
Forward incoming HTTP traffic:
# firewall-cmd --zone=public --add-forward-port=port=80:proto=tcp:toaddr=198.51.100.10:toport=8080 --permanent
The previous command defines a DNAT rule with the following settings:
-
--zone=public
- The firewall zone for which you configure the DNAT rule. You can adjust this to whatever zone you need. -
--add-forward-port
- The option that indicates you are adding a port-forwarding rule. -
port=80
- The external destination port. -
proto=tcp
- The protocol indicating that you forward TCP traffic. -
toaddr=198.51.100.10
- The destination IP address. -
toport=8080
- The destination port of the internal server. -
--permanent
- The option that makes the DNAT rule persistent across reboots.
-
Reload the firewall configuration to apply the changes:
# firewall-cmd --reload
Verification
Verify the DNAT rule for the firewall zone that you used:
# firewall-cmd --list-forward-ports --zone=public port=80:proto=tcp:toport=8080:toaddr=198.51.100.10
Alternatively, view the corresponding XML configuration file:
# cat /etc/firewalld/zones/public.xml <?xml version="1.0" encoding="utf-8"?> <zone> <short>Public</short> <description>For use in public areas. You do not trust the other computers on networks to not harm your computer. Only selected incoming connections are accepted.</description> <service name="ssh"/> <service name="dhcpv6-client"/> <service name="cockpit"/> <forward-port port="80" protocol="tcp" to-port="8080" to-addr="198.51.100.10"/> <forward/> </zone>
Additional resources
- Configuring kernel parameters at runtime
-
firewall-cmd(1)
manual page
40.11.4. Redirecting traffic from a non-standard port to make the web service accessible on a standard port
You can use the redirect mechanism to make the web service that internally runs on a non-standard port accessible without requiring users to specify the port in the URL. As a result, the URLs are simpler and provide better browsing experience, while a non-standard port is still used internally or for specific requirements.
Prerequisites
-
The
firewalld
service is running.
Procedure
Create the
/etc/sysctl.d/90-enable-IP-forwarding.conf
file with the following content:net.ipv4.ip_forward=1
This setting enables IP forwarding in the kernel.
Load the setting from the
/etc/sysctl.d/90-enable-IP-forwarding.conf
file:# sysctl -p /etc/sysctl.d/90-enable-IP-forwarding.conf
Create the NAT redirect rule:
# firewall-cmd --zone=public --add-forward-port=port=<standard_port>:proto=tcp:toport=<non_standard_port> --permanent
The previous command defines the NAT redirect rule with the following settings:
-
--zone=public
- The firewall zone, for which you configure the rule. You can adjust this to whatever zone you need. -
--add-forward-port=port=<non_standard_port>
- The option that indicates you are adding a port-forwarding (redirecting) rule with source port on which you initially receive the incoming traffic. -
proto=tcp
- The protocol indicating that you redirect TCP traffic. -
toport=<standard_port>
- The destination port, to which the incoming traffic should be redirected after being received on the source port. -
--permanent
- The option that makes the rule persist across reboots.
-
Reload the firewall configuration to apply the changes:
# firewall-cmd --reload
Verification
Verify the redirect rule for the firewall zone that you used:
# firewall-cmd --list-forward-ports port=8080:proto=tcp:toport=80:toaddr=
Alternatively, view the corresponding XML configuration file:
# cat /etc/firewalld/zones/public.xml <?xml version="1.0" encoding="utf-8"?> <zone> <short>Public</short> <description>For use in public areas. You do not trust the other computers on networks to not harm your computer. Only selected incoming connections are accepted.</description> <service name="ssh"/> <service name="dhcpv6-client"/> <service name="cockpit"/> <forward-port port="8080" protocol="tcp" to-port="80"/> <forward/> </zone>
Additional resources
- Configuring kernel parameters at runtime
-
firewall-cmd(1)
manual page
40.12. Managing ICMP requests
The Internet Control Message Protocol
(ICMP
) is a supporting protocol that is used by various network devices for testing, troubleshooting, and diagnostics. ICMP
differs from transport protocols such as TCP and UDP because it is not used to exchange data between systems.
You can use the ICMP
messages, especially echo-request
and echo-reply
, to reveal information about a network and misuse such information for various kinds of fraudulent activities. Therefore, firewalld
enables controlling the ICMP
requests to protect your network information.
40.12.1. Configuring ICMP filtering
You can use ICMP filtering to define which ICMP types and codes you want the firewall to permit or deny from reaching your system. ICMP types and codes are specific categories and subcategories of ICMP messages.
ICMP filtering helps, for example, in the following areas:
- Security enhancement - Block potentially harmful ICMP types and codes to reduce your attack surface.
- Network performance - Permit only necessary ICMP types to optimize network performance and prevent potential network congestion caused by excessive ICMP traffic.
- Troubleshooting control - Maintain essential ICMP functionality for network troubleshooting and block ICMP types that represent potential security risk.
Prerequisites
-
The
firewalld
service is running.
Procedure
List available ICMP types and codes:
# firewall-cmd --get-icmptypes address-unreachable bad-header beyond-scope communication-prohibited destination-unreachable echo-reply echo-request failed-policy fragmentation-needed host-precedence-violation host-prohibited host-redirect host-unknown host-unreachable ...
From this predefined list, select which ICMP types and codes to allow or block.
Filter specific ICMP types by:
Allowing ICMP types:
# firewall-cmd --zone=<target-zone> --remove-icmp-block=echo-request --permanent
The command removes any existing blocking rules for the echo requests ICMP type.
Blocking ICMP types:
# firewall-cmd --zone=<target-zone> --add-icmp-block=redirect --permanent
The command ensures that the redirect messages ICMP type is blocked by the firewall.
Reload the firewall configuration to apply the changes:
# firewall-cmd --reload
Verification
Verify your filtering rules are in effect:
# firewall-cmd --list-icmp-blocks redirect
The command output displays the ICMP types and codes that you allowed or blocked.
Additional resources
-
firewall-cmd(1)
manual page
40.13. Setting and controlling IP sets using firewalld
IP sets are a RHEL feature for grouping of IP addresses and networks into sets to achieve more flexible and efficient firewall rule management.
The IP sets are valuable in scenarios when you need to for example:
- Handle large lists of IP addresses
- Implement dynamic updates to those large lists of IP addresses
- Create custom IP-based policies to enhance network security and control
Red Hat recommends using the firewall-cmd
command to create and manage IP sets.
40.13.1. Configuring dynamic updates for allowlisting with IP sets
You can make near real-time updates to flexibly allow specific IP addresses or ranges in the IP sets even in unpredictable conditions. These updates can be triggered by various events, such as detection of security threats or changes in the network behavior. Typically, such a solution leverages automation to reduce manual effort and improve security by responding quickly to the situation.
Prerequisites
-
The
firewalld
service is running.
Procedure
Create an IP set with a meaningful name:
# firewall-cmd --permanent --new-ipset=allowlist --type=hash:ip
The new IP set called
allowlist
contains IP addresses that you want your firewall to allow.Add a dynamic update to the IP set:
# firewall-cmd --permanent --ipset=allowlist --add-entry=198.51.100.10
This configuration updates the
allowlist
IP set with a newly added IP address that is allowed to pass network traffic by your firewall.Create a firewall rule that references the previously created IP set:
# firewall-cmd --permanent --zone=public --add-source=ipset:allowlist
Without this rule, the IP set would not have any impact on network traffic. The default firewall policy would prevail.
Reload the firewall configuration to apply the changes:
# firewall-cmd --reload
Verification
List all IP sets:
# firewall-cmd --get-ipsets allowlist
List the active rules:
# firewall-cmd --list-all public (active) target: default icmp-block-inversion: no interfaces: enp0s1 sources: ipset:allowlist services: cockpit dhcpv6-client ssh ports: protocols: ...
The
sources
section of the command-line output provides insights to what origins of traffic (hostnames, interfaces, IP sets, subnets, and others) are permitted or denied access to a particular firewall zone. In this case, the IP addresses contained in theallowlist
IP set are allowed to pass traffic through the firewall for thepublic
zone.Explore the contents of your IP set:
# cat /etc/firewalld/ipsets/allowlist.xml <?xml version="1.0" encoding="utf-8"?> <ipset type="hash:ip"> <entry>198.51.100.10</entry> </ipset>
Next steps
-
Use a script or a security utility to fetch your threat intelligence feeds and update
allowlist
accordingly in an automated fashion.
Additional resources
-
firewall-cmd(1)
manual page
40.14. Prioritizing rich rules
By default, rich rules are organized based on their rule action. For example, deny
rules have precedence over allow
rules. The priority
parameter in rich rules provides administrators fine-grained control over rich rules and their execution order. When using the priority
parameter, rules are sorted first by their priority values in ascending order. When more rules have the same priority
, their order is determined by the rule action, and if the action is also the same, the order may be undefined.
40.14.1. How the priority parameter organizes rules into different chains
You can set the priority
parameter in a rich rule to any number between -32768
and 32767
, and lower numerical values have higher precedence.
The firewalld
service organizes rules based on their priority value into different chains:
-
Priority lower than 0: the rule is redirected into a chain with the
_pre
suffix. -
Priority higher than 0: the rule is redirected into a chain with the
_post
suffix. -
Priority equals 0: based on the action, the rule is redirected into a chain with the
_log
,_deny
, or_allow
the action.
Inside these sub-chains, firewalld
sorts the rules based on their priority value.
40.14.2. Setting the priority of a rich rule
The following is an example of how to create a rich rule that uses the priority
parameter to log all traffic that is not allowed or denied by other rules. You can use this rule to flag unexpected traffic.
Procedure
Add a rich rule with a very low precedence to log all traffic that has not been matched by other rules:
# firewall-cmd --add-rich-rule='rule priority=32767 log prefix="UNEXPECTED: " limit value="5/m"'
The command additionally limits the number of log entries to
5
per minute.
Verification
Display the
nftables
rule that the command in the previous step created:# nft list chain inet firewalld filter_IN_public_post table inet firewalld { chain filter_IN_public_post { log prefix "UNEXPECTED: " limit rate 5/minute } }
40.15. Configuring firewall lockdown
Local applications or services are able to change the firewall configuration if they are running as root
(for example, libvirt). With this feature, the administrator can lock the firewall configuration so that either no applications or only applications that are added to the lockdown allow list are able to request firewall changes. The lockdown settings default to disabled. If enabled, the user can be sure that there are no unwanted configuration changes made to the firewall by local applications or services.
40.15.1. Configuring lockdown using CLI
You can enable or disable the lockdown feature using the command line.
Procedure
To query whether lockdown is enabled:
# firewall-cmd --query-lockdown
Manage lockdown configuration by either:
Enabling lockdown:
# firewall-cmd --lockdown-on
Disabling lockdown:
# firewall-cmd --lockdown-off
40.15.2. Overview of lockdown allowlist configuration files
The default allowlist configuration file contains the NetworkManager
context and the default context of libvirt
. The user ID 0 is also on the list.
The allowlist configuration files are stored in the /etc/firewalld/
directory.
<?xml version="1.0" encoding="utf-8"?> <whitelist> <command name="/usr/bin/python3 -s /usr/bin/firewall-config"/> <selinux context="system_u:system_r:NetworkManager_t:s0"/> <selinux context="system_u:system_r:virtd_t:s0-s0:c0.c1023"/> <user id="0"/> </whitelist>
Following is an example allowlist configuration file enabling all commands for the firewall-cmd
utility, for a user called user whose user ID is 815
:
<?xml version="1.0" encoding="utf-8"?> <whitelist> <command name="/usr/libexec/platform-python -s /bin/firewall-cmd*"/> <selinux context="system_u:system_r:NetworkManager_t:s0"/> <user id="815"/> <user name="user"/> </whitelist>
This example shows both user id
and user name
, but only one option is required. Python is the interpreter and is prepended to the command line.
In Red Hat Enterprise Linux, all utilities are placed in the /usr/bin/
directory and the /bin/
directory is sym-linked to the /usr/bin/
directory. In other words, although the path for firewall-cmd
when entered as root
might resolve to /bin/firewall-cmd
, /usr/bin/firewall-cmd
can now be used. All new scripts should use the new location. But be aware that if scripts that run as root
are written to use the /bin/firewall-cmd
path, then that command path must be added in the allowlist in addition to the /usr/bin/firewall-cmd
path traditionally used only for non-root
users.
The *
at the end of the name attribute of a command means that all commands that start with this string match. If the *
is not there then the absolute command including arguments must match.
40.16. Enabling traffic forwarding between different interfaces or sources within a firewalld zone
Intra-zone forwarding is a firewalld
feature that enables traffic forwarding between interfaces or sources within a firewalld
zone.
40.16.1. The difference between intra-zone forwarding and zones with the default target set to ACCEPT
With intra-zone forwarding enabled, the traffic within a single firewalld
zone can flow from one interface or source to another interface or source. The zone specifies the trust level of interfaces and sources. If the trust level is the same, the traffic stays inside the same zone.
Enabling intra-zone forwarding in the default zone of firewalld
, applies only to the interfaces and sources added to the current default zone.
firewalld
uses different zones to manage incoming and outgoing traffic. Each zone has its own set of rules and behaviors. For example, the trusted
zone, allows all forwarded traffic by default.
Other zones can have different default behaviors. In standard zones, forwarded traffic is typically dropped by default when the target of the zone is set to default
.
To control how the traffic is forwarded between different interfaces or sources within a zone, make sure you understand and configure the target of the zone accordingly.
40.16.2. Using intra-zone forwarding to forward traffic between an Ethernet and Wi-Fi network
You can use intra-zone forwarding to forward traffic between interfaces and sources within the same firewalld
zone. This feature brings the following benefits:
-
Seamless connectivity between wired and wireless devices (you can forward traffic between an Ethernet network connected to
enp1s0
and a Wi-Fi network connected towlp0s20
) - Support for flexible work environments
- Shared resources that are accessible and used by multiple devices or users within a network (such as printers, databases, network-attached storage, and others)
- Efficient internal networking (such as smooth communication, reduced latency, resource accessibility, and others)
You can enable this functionality for individual firewalld
zones.
Procedure
Enable packet forwarding in the kernel:
# echo "net.ipv4.ip_forward=1" > /etc/sysctl.d/95-IPv4-forwarding.conf # sysctl -p /etc/sysctl.d/95-IPv4-forwarding.conf
Ensure that interfaces between which you want to enable intra-zone forwarding are assigned only to the
internal
zone:# firewall-cmd --get-active-zones
If the interface is currently assigned to a zone other than
internal
, reassign it:# firewall-cmd --zone=internal --change-interface=interface_name --permanent
Add the
enp1s0
andwlp0s20
interfaces to theinternal
zone:# firewall-cmd --zone=internal --add-interface=enp1s0 --add-interface=wlp0s20
Enable intra-zone forwarding:
# firewall-cmd --zone=internal --add-forward
Verification
The following Verification require that the nmap-ncat
package is installed on both hosts.
-
Log in to a host that is on the same network as the
enp1s0
interface of the host on which you enabled zone forwarding. Start an echo service with
ncat
to test connectivity:# ncat -e /usr/bin/cat -l 12345
-
Log in to a host that is in the same network as the
wlp0s20
interface. Connect to the echo server running on the host that is in the same network as the
enp1s0
:# ncat <other_host> 12345
- Type something and press . Verify the text is sent back.
Additional resources
-
firewalld.zones(5)
man page
40.17. Configuring firewalld
by using the RHEL system role
You can use the firewall
RHEL system role to configure settings of the firewalld
service on multiple clients at once. This solution:
- Provides an interface with efficient input settings.
-
Keeps all intended
firewalld
parameters in one place.
After you run the firewall
role on the control node, the RHEL system role applies the firewalld
parameters to the managed node immediately and makes them persistent across reboots.
40.17.1. Introduction to the firewall
RHEL system role
RHEL system roles is a set of contents for the Ansible automation utility. This content together with the Ansible automation utility provides a consistent configuration interface to remotely manage multiple systems.
The rhel-system-roles.firewall
role from the RHEL system roles was introduced for automated configurations of the firewalld
service. The rhel-system-roles
package contains this RHEL system role, and also the reference documentation.
To apply the firewalld
parameters on one or more systems in an automated fashion, use the firewall
RHEL system role variable in a playbook. A playbook is a list of one or more plays that is written in the text-based YAML format.
You can use an inventory file to define a set of systems that you want Ansible to configure.
With the firewall
role you can configure many different firewalld
parameters, for example:
- Zones.
- The services for which packets should be allowed.
- Granting, rejection, or dropping of traffic access to ports.
- Forwarding of ports or port ranges for a zone.
Additional resources
-
/usr/share/ansible/roles/rhel-system-roles.firewall/README.md
file -
/usr/share/doc/rhel-system-roles/firewall/
directory - Working with playbooks
- How to build your inventory
40.17.2. Resetting the firewalld
settings by using the firewall
RHEL system role
With the firewall
RHEL system role, you can reset the firewalld
settings to their default state. If you add the previous:replaced
parameter to the variable list, the RHEL system role removes all existing user-defined settings and resets firewalld
to the defaults. If you combine the previous:replaced
parameter with other settings, the firewall
role removes all existing settings before applying new ones.
Perform this procedure on the Ansible control node.
Prerequisites
- You have prepared the control node and the managed nodes
- You are logged in to the control node as a user who can run playbooks on the managed nodes.
-
The account you use to connect to the managed nodes has
sudo
permissions on them.
Procedure
Create a playbook file, for example
~/playbook.yml
, with the following content:--- - name: Reset firewalld example hosts: managed-node-01.example.com tasks: - name: Reset firewalld ansible.builtin.include_role: name: rhel-system-roles.firewall vars: firewall: - previous: replaced
Validate the playbook syntax:
$ ansible-playbook --syntax-check ~/playbook.yml
Note that this command only validates the syntax and does not protect against a wrong but valid configuration.
Run the playbook:
$ ansible-playbook ~/playbook.yml
Verification
Run this command as
root
on the managed node to check all the zones:# firewall-cmd --list-all-zones
Additional resources
-
/usr/share/ansible/roles/rhel-system-roles.firewall/README.md
file -
/usr/share/doc/rhel-system-roles/firewall/
directory
40.17.3. Forwarding incoming traffic in firewalld
from one local port to a different local port by using the firewall
RHEL system role
With the firewall
role you can remotely configure firewalld
parameters with persisting effect on multiple managed hosts.
Perform this procedure on the Ansible control node.
Prerequisites
- You have prepared the control node and the managed nodes
- You are logged in to the control node as a user who can run playbooks on the managed nodes.
-
The account you use to connect to the managed nodes has
sudo
permissions on them.
Procedure
Create a playbook file, for example
~/playbook.yml
, with the following content:--- - name: Configure firewalld hosts: managed-node-01.example.com tasks: - name: Forward incoming traffic on port 8080 to 443 ansible.builtin.include_role: name: rhel-system-roles.firewall vars: firewall: - { forward_port: 8080/tcp;443;, state: enabled, runtime: true, permanent: true }
Validate the playbook syntax:
$ ansible-playbook --syntax-check ~/playbook.yml
Note that this command only validates the syntax and does not protect against a wrong but valid configuration.
Run the playbook:
$ ansible-playbook ~/playbook.yml
Verification
On the managed host, display the
firewalld
settings:# firewall-cmd --list-forward-ports
Additional resources
-
/usr/share/ansible/roles/rhel-system-roles.firewall/README.md
file -
/usr/share/doc/rhel-system-roles/firewall/
directory
40.17.4. Managing ports in firewalld
by using the firewall
RHEL system role
You can use the firewall
RHEL system role to open or close ports in the local firewall for incoming traffic and make the new configuration persist across reboots. For example you can configure the default zone to permit incoming traffic for the HTTPS service.
Perform this procedure on the Ansible control node.
Prerequisites
- You have prepared the control node and the managed nodes
- You are logged in to the control node as a user who can run playbooks on the managed nodes.
-
The account you use to connect to the managed nodes has
sudo
permissions on them.
Procedure
Create a playbook file, for example
~/playbook.yml
, with the following content:--- - name: Configure firewalld hosts: managed-node-01.example.com tasks: - name: Allow incoming HTTPS traffic to the local host ansible.builtin.include_role: name: rhel-system-roles.firewall vars: firewall: - port: 443/tcp service: http state: enabled runtime: true permanent: true
The
permanent: true
option makes the new settings persistent across reboots.Validate the playbook syntax:
$ ansible-playbook --syntax-check ~/playbook.yml
Note that this command only validates the syntax and does not protect against a wrong but valid configuration.
Run the playbook:
$ ansible-playbook ~/playbook.yml
Verification
On the managed node, verify that the
443/tcp
port associated with theHTTPS
service is open:# firewall-cmd --list-ports 443/tcp
Additional resources
-
/usr/share/ansible/roles/rhel-system-roles.firewall/README.md
file -
/usr/share/doc/rhel-system-roles/firewall/
directory
40.17.5. Configuring a firewalld
DMZ zone by using the firewall
RHEL system role
As a system administrator, you can use the firewall
RHEL system role to configure a dmz
zone on the enp1s0 interface to permit HTTPS
traffic to the zone. In this way, you enable external users to access your web servers.
Perform this procedure on the Ansible control node.
Prerequisites
- You have prepared the control node and the managed nodes
- You are logged in to the control node as a user who can run playbooks on the managed nodes.
-
The account you use to connect to the managed nodes has
sudo
permissions on them.
Procedure
Create a playbook file, for example
~/playbook.yml
, with the following content:--- - name: Configure firewalld hosts: managed-node-01.example.com tasks: - name: Creating a DMZ with access to HTTPS port and masquerading for hosts in DMZ ansible.builtin.include_role: name: rhel-system-roles.firewall vars: firewall: - zone: dmz interface: enp1s0 service: https state: enabled runtime: true permanent: true
Validate the playbook syntax:
$ ansible-playbook --syntax-check ~/playbook.yml
Note that this command only validates the syntax and does not protect against a wrong but valid configuration.
Run the playbook:
$ ansible-playbook ~/playbook.yml
Verification
On the managed node, view detailed information about the
dmz
zone:# firewall-cmd --zone=dmz --list-all dmz (active) target: default icmp-block-inversion: no interfaces: enp1s0 sources: services: https ssh ports: protocols: forward: no masquerade: no forward-ports: source-ports: icmp-blocks:
Additional resources
-
/usr/share/ansible/roles/rhel-system-roles.firewall/README.md
file -
/usr/share/doc/rhel-system-roles/firewall/
directory
Chapter 41. Getting started with nftables
The nftables
framework classifies packets and it is the successor to the iptables
, ip6tables
, arptables
, ebtables
, and ipset
utilities. It offers numerous improvements in convenience, features, and performance over previous packet-filtering tools, most notably:
- Built-in lookup tables instead of linear processing
-
A single framework for both the
IPv4
andIPv6
protocols - All rules applied atomically instead of fetching, updating, and storing a complete rule set
-
Support for debugging and tracing in the rule set (
nftrace
) and monitoring trace events (in thenft
tool) - More consistent and compact syntax, no protocol-specific extensions
- A Netlink API for third-party applications
The nftables
framework uses tables to store chains. The chains contain individual rules for performing actions. The nft
utility replaces all tools from the previous packet-filtering frameworks. You can use the libnftnl
library for low-level interaction with nftables
Netlink API through the libmnl
library.
To display the effect of rule set changes, use the nft list ruleset
command. Because these utilities add tables, chains, rules, sets, and other objects to the nftables
rule set, be aware that nftables
rule-set operations, such as the nft flush ruleset
command, might affect rule sets installed using the iptables
command.
41.1. Migrating from iptables to nftables
If your firewall configuration still uses iptables
rules, you can migrate your iptables
rules to nftables
.
41.1.1. When to use firewalld, nftables, or iptables
The following is a brief overview in which scenario you should use one of the following utilities:
-
firewalld
: Use thefirewalld
utility for simple firewall use cases. The utility is easy to use and covers the typical use cases for these scenarios. -
nftables
: Use thenftables
utility to set up complex and performance-critical firewalls, such as for a whole network. -
iptables
: Theiptables
utility on Red Hat Enterprise Linux uses thenf_tables
kernel API instead of thelegacy
back end. Thenf_tables
API provides backward compatibility so that scripts that useiptables
commands still work on Red Hat Enterprise Linux. For new firewall scripts, Red Hat recommends to usenftables
.
To prevent the different firewall-related services (firewalld
, nftables
, or iptables
) from influencing each other, run only one of them on a RHEL host, and disable the other services.
41.1.2. Converting iptables and ip6tables rule sets to nftables
Use the iptables-restore-translate
and ip6tables-restore-translate
utilities to translate iptables
and ip6tables
rule sets to nftables
.
Prerequisites
-
The
nftables
andiptables
packages are installed. -
The system has
iptables
andip6tables
rules configured.
Procedure
Write the
iptables
andip6tables
rules to a file:# iptables-save >/root/iptables.dump # ip6tables-save >/root/ip6tables.dump
Convert the dump files to
nftables
instructions:# iptables-restore-translate -f /root/iptables.dump > /etc/nftables/ruleset-migrated-from-iptables.nft # ip6tables-restore-translate -f /root/ip6tables.dump > /etc/nftables/ruleset-migrated-from-ip6tables.nft
-
Review and, if needed, manually update the generated
nftables
rules. To enable the
nftables
service to load the generated files, add the following to the/etc/sysconfig/nftables.conf
file:include "/etc/nftables/ruleset-migrated-from-iptables.nft" include "/etc/nftables/ruleset-migrated-from-ip6tables.nft"
Stop and disable the
iptables
service:# systemctl disable --now iptables
If you used a custom script to load the
iptables
rules, ensure that the script no longer starts automatically and reboot to flush all tables.Enable and start the
nftables
service:# systemctl enable --now nftables
Verification
Display the
nftables
rule set:# nft list ruleset
Additional resources
41.1.3. Converting single iptables and ip6tables rules to nftables
Red Hat Enterprise Linux provides the iptables-translate
and ip6tables-translate
utilities to convert an iptables
or ip6tables
rule into the equivalent one for nftables
.
Prerequisites
-
The
nftables
package is installed.
Procedure
Use the
iptables-translate
orip6tables-translate
utility instead ofiptables
orip6tables
to display the correspondingnftables
rule, for example:# iptables-translate -A INPUT -s 192.0.2.0/24 -j ACCEPT nft add rule ip filter INPUT ip saddr 192.0.2.0/24 counter accept
Note that some extensions lack translation support. In these cases, the utility prints the untranslated rule prefixed with the
#
sign, for example:# iptables-translate -A INPUT -j CHECKSUM --checksum-fill nft # -A INPUT -j CHECKSUM --checksum-fill
Additional resources
-
iptables-translate --help
41.1.4. Comparison of common iptables and nftables commands
The following is a comparison of common iptables
and nftables
commands:
Listing all rules:
iptables nftables iptables-save
nft list ruleset
Listing a certain table and chain:
iptables nftables iptables -L
nft list table ip filter
iptables -L INPUT
nft list chain ip filter INPUT
iptables -t nat -L PREROUTING
nft list chain ip nat PREROUTING
The
nft
command does not pre-create tables and chains. They exist only if a user created them manually.Listing rules generated by firewalld:
# nft list table inet firewalld # nft list table ip firewalld # nft list table ip6 firewalld
41.2. Writing and executing nftables scripts
The major benefit of using the nftables
framework is that the execution of scripts is atomic. This means that the system either applies the whole script or prevents the execution if an error occurs. This guarantees that the firewall is always in a consistent state.
Additionally, with the nftables
script environment, you can:
- Add comments
- Define variables
- Include other rule-set files
When you install the nftables
package, Red Hat Enterprise Linux automatically creates *.nft
scripts in the /etc/nftables/
directory. These scripts contain commands that create tables and empty chains for different purposes.
41.2.1. Supported nftables script formats
You can write scripts in the nftables
scripting environment in the following formats:
The same format as the
nft list ruleset
command displays the rule set:#!/usr/sbin/nft -f # Flush the rule set flush ruleset table inet example_table { chain example_chain { # Chain for incoming packets that drops all packets that # are not explicitly allowed by any rule in this chain type filter hook input priority 0; policy drop; # Accept connections to port 22 (ssh) tcp dport ssh accept } }
The same syntax as for
nft
commands:#!/usr/sbin/nft -f # Flush the rule set flush ruleset # Create a table add table inet example_table # Create a chain for incoming packets that drops all packets # that are not explicitly allowed by any rule in this chain add chain inet example_table example_chain { type filter hook input priority 0 ; policy drop ; } # Add a rule that accepts connections to port 22 (ssh) add rule inet example_table example_chain tcp dport ssh accept
41.2.2. Running nftables scripts
You can run an nftables
script either by passing it to the nft
utility or by executing the script directly.
Procedure
To run an
nftables
script by passing it to thenft
utility, enter:# nft -f /etc/nftables/<example_firewall_script>.nft
To run an
nftables
script directly:For the single time that you perform this:
Ensure that the script starts with the following shebang sequence:
#!/usr/sbin/nft -f
ImportantIf you omit the
-f
parameter, thenft
utility does not read the script and displays:Error: syntax error, unexpected newline, expecting string
.Optional: Set the owner of the script to
root
:# chown root /etc/nftables/<example_firewall_script>.nft
Make the script executable for the owner:
# chmod u+x /etc/nftables/<example_firewall_script>.nft
Run the script:
# /etc/nftables/<example_firewall_script>.nft
If no output is displayed, the system executed the script successfully.
Even if nft
executes the script successfully, incorrectly placed rules, missing parameters, or other problems in the script can cause that the firewall behaves not as expected.
Additional resources
-
chown(1)
man page -
chmod(1)
man page - Automatically loading nftables rules when the system boots
41.2.3. Using comments in nftables scripts
The nftables
scripting environment interprets everything to the right of a #
character to the end of a line as a comment.
Comments can start at the beginning of a line, or next to a command:
... # Flush the rule set flush ruleset add table inet example_table # Create a table ...
41.2.4. Using variables in nftables script
To define a variable in an nftables
script, use the define
keyword. You can store single values and anonymous sets in a variable. For more complex scenarios, use sets or verdict maps.
- Variables with a single value
The following example defines a variable named
INET_DEV
with the valueenp1s0
:define INET_DEV = enp1s0
You can use the variable in the script by entering the
$
sign followed by the variable name:... add rule inet example_table example_chain iifname $INET_DEV tcp dport ssh accept ...
- Variables that contain an anonymous set
The following example defines a variable that contains an anonymous set:
define DNS_SERVERS = { 192.0.2.1, 192.0.2.2 }
You can use the variable in the script by writing the
$
sign followed by the variable name:add rule inet example_table example_chain ip daddr $DNS_SERVERS accept
NoteCurly braces have special semantics when you use them in a rule because they indicate that the variable represents a set.
Additional resources
41.2.5. Including files in nftables scripts
In the nftables
scripting environment, you can include other scripts by using the include
statement.
If you specify only a file name without an absolute or relative path, nftables
includes files from the default search path, which is set to /etc
on Red Hat Enterprise Linux.
Example 41.1. Including files from the default search directory
To include a file from the default search directory:
include "example.nft"
Example 41.2. Including all *.nft files from a directory
To include all files ending with *.nft
that are stored in the /etc/nftables/rulesets/
directory:
include "/etc/nftables/rulesets/*.nft"
Note that the include
statement does not match files beginning with a dot.
Additional resources
-
The
Include files
section in thenft(8)
man page
41.2.6. Automatically loading nftables rules when the system boots
The nftables
systemd service loads firewall scripts that are included in the /etc/sysconfig/nftables.conf
file.
Prerequisites
-
The
nftables
scripts are stored in the/etc/nftables/
directory.
Procedure
Edit the
/etc/sysconfig/nftables.conf
file.-
If you modified the
*.nft
scripts that were created in/etc/nftables/
with the installation of thenftables
package, uncomment theinclude
statement for these scripts. If you wrote new scripts, add
include
statements to include these scripts. For example, to load the/etc/nftables/example.nft
script when thenftables
service starts, add:include "/etc/nftables/_example_.nft"
-
If you modified the
Optional: Start the
nftables
service to load the firewall rules without rebooting the system:# systemctl start nftables
Enable the
nftables
service.# systemctl enable nftables
Additional resources
41.3. Creating and managing nftables tables, chains, and rules
You can display nftables
rule sets and manage them.
41.3.1. Basics of nftables tables
A table in nftables
is a namespace that contains a collection of chains, rules, sets, and other objects.
Each table must have an address family assigned. The address family defines the packet types that this table processes. You can set one of the following address families when you create a table:
-
ip
: Matches only IPv4 packets. This is the default if you do not specify an address family. -
ip6
: Matches only IPv6 packets. -
inet
: Matches both IPv4 and IPv6 packets. -
arp
: Matches IPv4 address resolution protocol (ARP) packets. -
bridge
: Matches packets that pass through a bridge device. -
netdev
: Matches packets from ingress.
If you want to add a table, the format to use depends on your firewall script:
In scripts in native syntax, use:
table <table_address_family> <table_name> { }
In shell scripts, use:
nft add table <table_address_family> <table_name>
41.3.2. Basics of nftables chains
Tables consist of chains which in turn are containers for rules. The following two rule types exists:
- Base chain: You can use base chains as an entry point for packets from the networking stack.
-
Regular chain: You can use regular chains as a
jump
target to better organize rules.
If you want to add a base chain to a table, the format to use depends on your firewall script:
In scripts in native syntax, use:
table <table_address_family> <table_name> { chain <chain_name> { type <type> hook <hook> priority <priority> policy <policy> ; } }
In shell scripts, use:
nft add chain <table_address_family> <table_name> <chain_name> { type <type> hook <hook> priority <priority> \; policy <policy> \; }
To avoid that the shell interprets the semicolons as the end of the command, place the
\
escape character in front of the semicolons.
Both examples create base chains. To create a regular chain, do not set any parameters in the curly brackets.
Chain types
The following are the chain types and an overview with which address families and hooks you can use them:
Type | Address families | Hooks | Description |
---|---|---|---|
| all | all | Standard chain type |
|
|
| Chains of this type perform native address translation based on connection tracking entries. Only the first packet traverses this chain type. |
|
|
| Accepted packets that traverse this chain type cause a new route lookup if relevant parts of the IP header have changed. |
Chain priorities
The priority parameter specifies the order in which packets traverse chains with the same hook value. You can set this parameter to an integer value or use a standard priority name.
The following matrix is an overview of the standard priority names and their numeric values, and with which address families and hooks you can use them:
Textual value | Numeric value | Address families | Hooks |
---|---|---|---|
|
|
| all |
|
|
| all |
|
|
|
|
|
|
| |
|
|
| all |
|
| all | |
|
|
| all |
|
|
|
|
|
|
| |
|
|
|
|
Chain policies
The chain policy defines whether nftables
should accept or drop packets if rules in this chain do not specify any action. You can set one of the following policies in a chain:
-
accept
(default) -
drop
41.3.3. Basics of nftables rules
Rules define actions to perform on packets that pass a chain that contains this rule. If the rule also contains matching expressions, nftables
performs the actions only if all previous expressions apply.
If you want to add a rule to a chain, the format to use depends on your firewall script:
In scripts in native syntax, use:
table <table_address_family> <table_name> { chain <chain_name> { type <type> hook <hook> priority <priority> ; policy <policy> ; <rule> } }
In shell scripts, use:
nft add rule <table_address_family> <table_name> <chain_name> <rule>
This shell command appends the new rule at the end of the chain. If you prefer to add a rule at the beginning of the chain, use the
nft insert
command instead ofnft add
.
41.3.4. Managing tables, chains, and rules using nft commands
To manage an nftables
firewall on the command line or in shell scripts, use the nft
utility.
The commands in this procedure do not represent a typical workflow and are not optimized. This procedure only demonstrates how to use nft
commands to manage tables, chains, and rules in general.
Procedure
Create a table named
nftables_svc
with theinet
address family so that the table can process both IPv4 and IPv6 packets:# nft add table inet nftables_svc
Add a base chain named
INPUT
, that processes incoming network traffic, to theinet nftables_svc
table:# nft add chain inet nftables_svc INPUT { type filter hook input priority filter \; policy accept \; }
To avoid that the shell interprets the semicolons as the end of the command, escape the semicolons using the
\
character.Add rules to the
INPUT
chain. For example, allow incoming TCP traffic on port 22 and 443, and, as the last rule of theINPUT
chain, reject other incoming traffic with an Internet Control Message Protocol (ICMP) port unreachable message:# nft add rule inet nftables_svc INPUT tcp dport 22 accept # nft add rule inet nftables_svc INPUT tcp dport 443 accept # nft add rule inet nftables_svc INPUT reject with icmpx type port-unreachable
If you enter the
nft add rule
commands as shown,nft
adds the rules in the same order to the chain as you run the commands.Display the current rule set including handles:
# nft -a list table inet nftables_svc table inet nftables_svc { # handle 13 chain INPUT { # handle 1 type filter hook input priority filter; policy accept; tcp dport 22 accept # handle 2 tcp dport 443 accept # handle 3 reject # handle 4 } }
Insert a rule before the existing rule with handle 3. For example, to insert a rule that allows TCP traffic on port 636, enter:
# nft insert rule inet nftables_svc INPUT position 3 tcp dport 636 accept
Append a rule after the existing rule with handle 3. For example, to insert a rule that allows TCP traffic on port 80, enter:
# nft add rule inet nftables_svc INPUT position 3 tcp dport 80 accept
Display the rule set again with handles. Verify that the later added rules have been added to the specified positions:
# nft -a list table inet nftables_svc table inet nftables_svc { # handle 13 chain INPUT { # handle 1 type filter hook input priority filter; policy accept; tcp dport 22 accept # handle 2 tcp dport 636 accept # handle 5 tcp dport 443 accept # handle 3 tcp dport 80 accept # handle 6 reject # handle 4 } }
Remove the rule with handle 6:
# nft delete rule inet nftables_svc INPUT handle 6
To remove a rule, you must specify the handle.
Display the rule set, and verify that the removed rule is no longer present:
# nft -a list table inet nftables_svc table inet nftables_svc { # handle 13 chain INPUT { # handle 1 type filter hook input priority filter; policy accept; tcp dport 22 accept # handle 2 tcp dport 636 accept # handle 5 tcp dport 443 accept # handle 3 reject # handle 4 } }
Remove all remaining rules from the
INPUT
chain:# nft flush chain inet nftables_svc INPUT
Display the rule set, and verify that the
INPUT
chain is empty:# nft list table inet nftables_svc table inet nftables_svc { chain INPUT { type filter hook input priority filter; policy accept } }
Delete the
INPUT
chain:# nft delete chain inet nftables_svc INPUT
You can also use this command to delete chains that still contain rules.
Display the rule set, and verify that the
INPUT
chain has been deleted:# nft list table inet nftables_svc table inet nftables_svc { }
Delete the
nftables_svc
table:# nft delete table inet nftables_svc
You can also use this command to delete tables that still contain chains.
NoteTo delete the entire rule set, use the
nft flush ruleset
command instead of manually deleting all rules, chains, and tables in separate commands.
Additional resources
nft(8)
man page
41.4. Configuring NAT using nftables
With nftables
, you can configure the following network address translation (NAT) types:
- Masquerading
- Source NAT (SNAT)
- Destination NAT (DNAT)
- Redirect
You can only use real interface names in iifname
and oifname
parameters, and alternative names (altname
) are not supported.
41.4.1. NAT types
These are the different network address translation (NAT) types:
- Masquerading and source NAT (SNAT)
Use one of these NAT types to change the source IP address of packets. For example, Internet Service Providers (ISPs) do not route private IP ranges, such as
10.0.0.0/8
. If you use private IP ranges in your network and users should be able to reach servers on the internet, map the source IP address of packets from these ranges to a public IP address.Masquerading and SNAT are very similar to one another. The differences are:
- Masquerading automatically uses the IP address of the outgoing interface. Therefore, use masquerading if the outgoing interface uses a dynamic IP address.
- SNAT sets the source IP address of packets to a specified IP and does not dynamically look up the IP of the outgoing interface. Therefore, SNAT is faster than masquerading. Use SNAT if the outgoing interface uses a fixed IP address.
- Destination NAT (DNAT)
- Use this NAT type to rewrite the destination address and port of incoming packets. For example, if your web server uses an IP address from a private IP range and is, therefore, not directly accessible from the internet, you can set a DNAT rule on the router to redirect incoming traffic to this server.
- Redirect
- This type is a special case of DNAT that redirects packets to the local machine depending on the chain hook. For example, if a service runs on a different port than its standard port, you can redirect incoming traffic from the standard port to this specific port.
41.4.2. Configuring masquerading using nftables
Masquerading enables a router to dynamically change the source IP of packets sent through an interface to the IP address of the interface. This means that if the interface gets a new IP assigned, nftables
automatically uses the new IP when replacing the source IP.
Replace the source IP of packets leaving the host through the ens3
interface to the IP set on ens3
.
Procedure
Create a table:
# nft add table nat
Add the
prerouting
andpostrouting
chains to the table:# nft add chain nat postrouting { type nat hook postrouting priority 100 \; }
ImportantEven if you do not add a rule to the
prerouting
chain, thenftables
framework requires this chain to match incoming packet replies.Note that you must pass the
--
option to thenft
command to prevent the shell from interpreting the negative priority value as an option of thenft
command.Add a rule to the
postrouting
chain that matches outgoing packets on theens3
interface:# nft add rule nat postrouting oifname "ens3" masquerade
41.4.3. Configuring source NAT using nftables
On a router, Source NAT (SNAT) enables you to change the IP of packets sent through an interface to a specific IP address. The router then replaces the source IP of outgoing packets.
Procedure
Create a table:
# nft add table nat
Add the
prerouting
andpostrouting
chains to the table:# nft add chain nat postrouting { type nat hook postrouting priority 100 \; }
ImportantEven if you do not add a rule to the
postrouting
chain, thenftables
framework requires this chain to match outgoing packet replies.Note that you must pass the
--
option to thenft
command to prevent the shell from interpreting the negative priority value as an option of thenft
command.Add a rule to the
postrouting
chain that replaces the source IP of outgoing packets throughens3
with192.0.2.1
:# nft add rule nat postrouting oifname "ens3" snat to 192.0.2.1
Additional resources
41.4.4. Configuring destination NAT using nftables
Destination NAT (DNAT) enables you to redirect traffic on a router to a host that is not directly accessible from the internet.
For example, with DNAT the router redirects incoming traffic sent to port 80
and 443
to a web server with the IP address 192.0.2.1
.
Procedure
Create a table:
# nft add table nat
Add the
prerouting
andpostrouting
chains to the table:# nft -- add chain nat prerouting { type nat hook prerouting priority -100 \; } # nft add chain nat postrouting { type nat hook postrouting priority 100 \; }
ImportantEven if you do not add a rule to the
postrouting
chain, thenftables
framework requires this chain to match outgoing packet replies.Note that you must pass the
--
option to thenft
command to prevent the shell from interpreting the negative priority value as an option of thenft
command.Add a rule to the
prerouting
chain that redirects incoming traffic to port80
and443
on theens3
interface of the router to the web server with the IP address192.0.2.1
:# nft add rule nat prerouting iifname ens3 tcp dport { 80, 443 } dnat to 192.0.2.1
Depending on your environment, add either a SNAT or masquerading rule to change the source address for packets returning from the web server to the sender:
If the
ens3
interface uses a dynamic IP addresses, add a masquerading rule:# nft add rule nat postrouting oifname "ens3" masquerade
If the
ens3
interface uses a static IP address, add a SNAT rule. For example, if theens3
uses the198.51.100.1
IP address:# nft add rule nat postrouting oifname "ens3" snat to 198.51.100.1
Enable packet forwarding:
# echo "net.ipv4.ip_forward=1" > /etc/sysctl.d/95-IPv4-forwarding.conf # sysctl -p /etc/sysctl.d/95-IPv4-forwarding.conf
Additional resources
41.4.5. Configuring a redirect using nftables
The redirect
feature is a special case of destination network address translation (DNAT) that redirects packets to the local machine depending on the chain hook.
For example, you can redirect incoming and forwarded traffic sent to port 22
of the local host to port 2222
.
Procedure
Create a table:
# nft add table nat
Add the
prerouting
chain to the table:# nft -- add chain nat prerouting { type nat hook prerouting priority -100 \; }
Note that you must pass the
--
option to thenft
command to prevent the shell from interpreting the negative priority value as an option of thenft
command.Add a rule to the
prerouting
chain that redirects incoming traffic on port22
to port2222
:# nft add rule nat prerouting tcp dport 22 redirect to 2222
Additional resources
41.4.6. Configuring flowtable by using nftables
The nftables
utility uses the netfilter
framework to provide network address translation (NAT) for network traffic and provides the fastpath feature-based flowtable
mechanism to accelerate packet forwarding.
The flowtable mechanism has the following features:
- Uses connection tracking to bypass the classic packet forwarding path.
- Avoids revisiting the routing table by bypassing the classic packet processing.
- Works only with TCP and UDP protocols.
- Hardware independent software fast path.
Procedure
Add an
example-table
table ofinet
family:# nft add table inet <example-table>
Add an
example-flowtable
flowtable withingress
hook andfilter
as a priority type:# nft add flowtable inet <example-table> <example-flowtable> { hook ingress priority filter \; devices = { enp1s0, enp7s0 } \; }
Add an
example-forwardchain
flow to the flowtable from a packet processing table:# nft add chain inet <example-table> <example-forwardchain> { type filter hook forward priority filter \; }
This command adds a flowtable of
filter
type withforward
hook andfilter
priority.Add a rule with
established
connection tracking state to offloadexample-flowtable
flow:# nft add rule inet <example-table> <example-forwardchain> ct state established flow add @<example-flowtable>
Verification
Verify the properties of
example-table
:# nft list table inet <example-table> table inet example-table { flowtable example-flowtable { hook ingress priority filter devices = { enp1s0, enp7s0 } } chain example-forwardchain { type filter hook forward priority filter; policy accept; ct state established flow add @example-flowtable } }
Additional resources
-
nft(8)
man page
41.5. Using sets in nftables commands
The nftables
framework natively supports sets. You can use sets, for example, if a rule should match multiple IP addresses, port numbers, interfaces, or any other match criteria.
41.5.1. Using anonymous sets in nftables
An anonymous set contains comma-separated values enclosed in curly brackets, such as { 22, 80, 443 }
, that you use directly in a rule. You can use anonymous sets also for IP addresses and any other match criteria.
The drawback of anonymous sets is that if you want to change the set, you must replace the rule. For a dynamic solution, use named sets as described in Using named sets in nftables.
Prerequisites
-
The
example_chain
chain and theexample_table
table in theinet
family exists.
Procedure
For example, to add a rule to
example_chain
inexample_table
that allows incoming traffic to port22
,80
, and443
:# nft add rule inet example_table example_chain tcp dport { 22, 80, 443 } accept
Optional: Display all chains and their rules in
example_table
:# nft list table inet example_table table inet example_table { chain example_chain { type filter hook input priority filter; policy accept; tcp dport { ssh, http, https } accept } }
41.5.2. Using named sets in nftables
The nftables
framework supports mutable named sets. A named set is a list or range of elements that you can use in multiple rules within a table. Another benefit over anonymous sets is that you can update a named set without replacing the rules that use the set.
When you create a named set, you must specify the type of elements the set contains. You can set the following types:
-
ipv4_addr
for a set that contains IPv4 addresses or ranges, such as192.0.2.1
or192.0.2.0/24
. -
ipv6_addr
for a set that contains IPv6 addresses or ranges, such as2001:db8:1::1
or2001:db8:1::1/64
. -
ether_addr
for a set that contains a list of media access control (MAC) addresses, such as52:54:00:6b:66:42
. -
inet_proto
for a set that contains a list of internet protocol types, such astcp
. -
inet_service
for a set that contains a list of internet services, such asssh
. -
mark
for a set that contains a list of packet marks. Packet marks can be any positive 32-bit integer value (0
to2147483647
).
Prerequisites
-
The
example_chain
chain and theexample_table
table exists.
Procedure
Create an empty set. The following examples create a set for IPv4 addresses:
To create a set that can store multiple individual IPv4 addresses:
# nft add set inet example_table example_set { type ipv4_addr \; }
To create a set that can store IPv4 address ranges:
# nft add set inet example_table example_set { type ipv4_addr \; flags interval \; }
ImportantTo prevent the shell from interpreting the semicolons as the end of the command, you must escape the semicolons with a backslash.
Optional: Create rules that use the set. For example, the following command adds a rule to the
example_chain
in theexample_table
that will drop all packets from IPv4 addresses inexample_set
.# nft add rule inet example_table example_chain ip saddr @example_set drop
Because
example_set
is still empty, the rule has currently no effect.Add IPv4 addresses to
example_set
:If you create a set that stores individual IPv4 addresses, enter:
# nft add element inet example_table example_set { 192.0.2.1, 192.0.2.2 }
If you create a set that stores IPv4 ranges, enter:
# nft add element inet example_table example_set { 192.0.2.0-192.0.2.255 }
When you specify an IP address range, you can alternatively use the Classless Inter-Domain Routing (CIDR) notation, such as
192.0.2.0/24
in the above example.
41.5.3. Additional resources
-
The
Sets
section in thenft(8)
man page
41.6. Using verdict maps in nftables commands
Verdict maps, which are also known as dictionaries, enable nft
to perform an action based on packet information by mapping match criteria to an action.
41.6.1. Using anonymous maps in nftables
An anonymous map is a { match_criteria : action }
statement that you use directly in a rule. The statement can contain multiple comma-separated mappings.
The drawback of an anonymous map is that if you want to change the map, you must replace the rule. For a dynamic solution, use named maps as described in Using named maps in nftables.
For example, you can use an anonymous map to route both TCP and UDP packets of the IPv4 and IPv6 protocol to different chains to count incoming TCP and UDP packets separately.
Procedure
Create a new table:
# nft add table inet example_table
Create the
tcp_packets
chain inexample_table
:# nft add chain inet example_table tcp_packets
Add a rule to
tcp_packets
that counts the traffic in this chain:# nft add rule inet example_table tcp_packets counter
Create the
udp_packets
chain inexample_table
# nft add chain inet example_table udp_packets
Add a rule to
udp_packets
that counts the traffic in this chain:# nft add rule inet example_table udp_packets counter
Create a chain for incoming traffic. For example, to create a chain named
incoming_traffic
inexample_table
that filters incoming traffic:# nft add chain inet example_table incoming_traffic { type filter hook input priority 0 \; }
Add a rule with an anonymous map to
incoming_traffic
:# nft add rule inet example_table incoming_traffic ip protocol vmap { tcp : jump tcp_packets, udp : jump udp_packets }
The anonymous map distinguishes the packets and sends them to the different counter chains based on their protocol.
To list the traffic counters, display
example_table
:# nft list table inet example_table table inet example_table { chain tcp_packets { counter packets 36379 bytes 2103816 } chain udp_packets { counter packets 10 bytes 1559 } chain incoming_traffic { type filter hook input priority filter; policy accept; ip protocol vmap { tcp : jump tcp_packets, udp : jump udp_packets } } }
The counters in the
tcp_packets
andudp_packets
chain display both the number of received packets and bytes.
41.6.2. Using named maps in nftables
The nftables
framework supports named maps. You can use these maps in multiple rules within a table. Another benefit over anonymous maps is that you can update a named map without replacing the rules that use it.
When you create a named map, you must specify the type of elements:
-
ipv4_addr
for a map whose match part contains an IPv4 address, such as192.0.2.1
. -
ipv6_addr
for a map whose match part contains an IPv6 address, such as2001:db8:1::1
. -
ether_addr
for a map whose match part contains a media access control (MAC) address, such as52:54:00:6b:66:42
. -
inet_proto
for a map whose match part contains an internet protocol type, such astcp
. -
inet_service
for a map whose match part contains an internet services name port number, such asssh
or22
. -
mark
for a map whose match part contains a packet mark. A packet mark can be any positive 32-bit integer value (0
to2147483647
). -
counter
for a map whose match part contains a counter value. The counter value can be any positive 64-bit integer value. -
quota
for a map whose match part contains a quota value. The quota value can be any positive 64-bit integer value.
For example, you can allow or drop incoming packets based on their source IP address. Using a named map, you require only a single rule to configure this scenario while the IP addresses and actions are dynamically stored in the map.
Procedure
Create a table. For example, to create a table named
example_table
that processes IPv4 packets:# nft add table ip example_table
Create a chain. For example, to create a chain named
example_chain
inexample_table
:# nft add chain ip example_table example_chain { type filter hook input priority 0 \; }
ImportantTo prevent the shell from interpreting the semicolons as the end of the command, you must escape the semicolons with a backslash.
Create an empty map. For example, to create a map for IPv4 addresses:
# nft add map ip example_table example_map { type ipv4_addr : verdict \; }
Create rules that use the map. For example, the following command adds a rule to
example_chain
inexample_table
that applies actions to IPv4 addresses which are both defined inexample_map
:# nft add rule example_table example_chain ip saddr vmap @example_map
Add IPv4 addresses and corresponding actions to
example_map
:# nft add element ip example_table example_map { 192.0.2.1 : accept, 192.0.2.2 : drop }
This example defines the mappings of IPv4 addresses to actions. In combination with the rule created above, the firewall accepts packet from
192.0.2.1
and drops packets from192.0.2.2
.Optional: Enhance the map by adding another IP address and action statement:
# nft add element ip example_table example_map { 192.0.2.3 : accept }
Optional: Remove an entry from the map:
# nft delete element ip example_table example_map { 192.0.2.1 }
Optional: Display the rule set:
# nft list ruleset table ip example_table { map example_map { type ipv4_addr : verdict elements = { 192.0.2.2 : drop, 192.0.2.3 : accept } } chain example_chain { type filter hook input priority filter; policy accept; ip saddr vmap @example_map } }
41.6.3. Additional resources
-
The
Maps
section in thenft(8)
man page
41.7. Example: Protecting a LAN and DMZ using an nftables script
Use the nftables
framework on a RHEL router to write and install a firewall script that protects the network clients in an internal LAN and a web server in a DMZ from unauthorized access from the internet and from other networks.
This example is only for demonstration purposes and describes a scenario with specific requirements.
Firewall scripts highly depend on the network infrastructure and security requirements. Use this example to learn the concepts of nftables
firewalls when you write scripts for your own environment.
41.7.1. Network conditions
The network in this example has the following conditions:
The router is connected to the following networks:
-
The internet through interface
enp1s0
-
The internal LAN through interface
enp7s0
-
The DMZ through
enp8s0
-
The internet through interface
-
The internet interface of the router has both a static IPv4 address (
203.0.113.1
) and IPv6 address (2001:db8:a::1
) assigned. -
The clients in the internal LAN use only private IPv4 addresses from the range
10.0.0.0/24
. Consequently, traffic from the LAN to the internet requires source network address translation (SNAT). -
The administrator PCs in the internal LAN use the IP addresses
10.0.0.100
and10.0.0.200
. -
The DMZ uses public IP addresses from the ranges
198.51.100.0/24
and2001:db8:b::/56
. -
The web server in the DMZ uses the IP addresses
198.51.100.5
and2001:db8:b::5
. - The router acts as a caching DNS server for hosts in the LAN and DMZ.
41.7.2. Security requirements to the firewall script
The following are the requirements to the nftables
firewall in the example network:
The router must be able to:
- Recursively resolve DNS queries.
- Perform all connections on the loopback interface.
Clients in the internal LAN must be able to:
- Query the caching DNS server running on the router.
- Access the HTTPS server in the DMZ.
- Access any HTTPS server on the internet.
- The PCs of the administrators must be able to access the router and every server in the DMZ using SSH.
The web server in the DMZ must be able to:
- Query the caching DNS server running on the router.
- Access HTTPS servers on the internet to download updates.
Hosts on the internet must be able to:
- Access the HTTPS servers in the DMZ.
Additionally, the following security requirements exists:
- Connection attempts that are not explicitly allowed should be dropped.
- Dropped packets should be logged.
41.7.3. Configuring logging of dropped packets to a file
By default, systemd
logs kernel messages, such as for dropped packets, to the journal. Additionally, you can configure the rsyslog
service to log such entries to a separate file. To ensure that the log file does not grow infinitely, configure a rotation policy.
Prerequisites
-
The
rsyslog
package is installed. -
The
rsyslog
service is running.
Procedure
Create the
/etc/rsyslog.d/nftables.conf
file with the following content::msg, startswith, "nft drop" -/var/log/nftables.log & stop
Using this configuration, the
rsyslog
service logs dropped packets to the/var/log/nftables.log
file instead of/var/log/messages
.Restart the
rsyslog
service:# systemctl restart rsyslog
Create the
/etc/logrotate.d/nftables
file with the following content to rotate/var/log/nftables.log
if the size exceeds 10 MB:/var/log/nftables.log { size +10M maxage 30 sharedscripts postrotate /usr/bin/systemctl kill -s HUP rsyslog.service >/dev/null 2>&1 || true endscript }
The
maxage 30
setting defines thatlogrotate
removes rotated logs older than 30 days during the next rotation operation.
Additional resources
-
rsyslog.conf(5)
man page -
logrotate(8)
man page
41.7.4. Writing and activating the nftables script
This example is an nftables
firewall script that runs on a RHEL router and protects the clients in an internal LAN and a web server in a DMZ. For details about the network and the requirements for the firewall used in the example, see Network conditions and Security requirements to the firewall script.
This nftables
firewall script is only for demonstration purposes. Do not use it without adapting it to your environments and security requirements.
Prerequisites
- The network is configured as described in Network conditions.
Procedure
Create the
/etc/nftables/firewall.nft
script with the following content:# Remove all rules flush ruleset # Table for both IPv4 and IPv6 rules table inet nftables_svc { # Define variables for the interface name define INET_DEV = enp1s0 define LAN_DEV = enp7s0 define DMZ_DEV = enp8s0 # Set with the IPv4 addresses of admin PCs set admin_pc_ipv4 { type ipv4_addr elements = { 10.0.0.100, 10.0.0.200 } } # Chain for incoming trafic. Default policy: drop chain INPUT { type filter hook input priority filter policy drop # Accept packets in established and related state, drop invalid packets ct state vmap { established:accept, related:accept, invalid:drop } # Accept incoming traffic on loopback interface iifname lo accept # Allow request from LAN and DMZ to local DNS server iifname { $LAN_DEV, $DMZ_DEV } meta l4proto { tcp, udp } th dport 53 accept # Allow admins PCs to access the router using SSH iifname $LAN_DEV ip saddr @admin_pc_ipv4 tcp dport 22 accept # Last action: Log blocked packets # (packets that were not accepted in previous rules in this chain) log prefix "nft drop IN : " } # Chain for outgoing traffic. Default policy: drop chain OUTPUT { type filter hook output priority filter policy drop # Accept packets in established and related state, drop invalid packets ct state vmap { established:accept, related:accept, invalid:drop } # Accept outgoing traffic on loopback interface oifname lo accept # Allow local DNS server to recursively resolve queries oifname $INET_DEV meta l4proto { tcp, udp } th dport 53 accept # Last action: Log blocked packets log prefix "nft drop OUT: " } # Chain for forwarding traffic. Default policy: drop chain FORWARD { type filter hook forward priority filter policy drop # Accept packets in established and related state, drop invalid packets ct state vmap { established:accept, related:accept, invalid:drop } # IPv4 access from LAN and internet to the HTTPS server in the DMZ iifname { $LAN_DEV, $INET_DEV } oifname $DMZ_DEV ip daddr 198.51.100.5 tcp dport 443 accept # IPv6 access from internet to the HTTPS server in the DMZ iifname $INET_DEV oifname $DMZ_DEV ip6 daddr 2001:db8:b::5 tcp dport 443 accept # Access from LAN and DMZ to HTTPS servers on the internet iifname { $LAN_DEV, $DMZ_DEV } oifname $INET_DEV tcp dport 443 accept # Last action: Log blocked packets log prefix "nft drop FWD: " } # Postrouting chain to handle SNAT chain postrouting { type nat hook postrouting priority srcnat; policy accept; # SNAT for IPv4 traffic from LAN to internet iifname $LAN_DEV oifname $INET_DEV snat ip to 203.0.113.1 } }
Include the
/etc/nftables/firewall.nft
script in the/etc/sysconfig/nftables.conf
file:include "/etc/nftables/firewall.nft"
Enable IPv4 forwarding:
# echo "net.ipv4.ip_forward=1" > /etc/sysctl.d/95-IPv4-forwarding.conf # sysctl -p /etc/sysctl.d/95-IPv4-forwarding.conf
Enable and start the
nftables
service:# systemctl enable --now nftables
Verification
Optional: Verify the
nftables
rule set:# nft list ruleset ...
Try to perform an access that the firewall prevents. For example, try to access the router using SSH from the DMZ:
# ssh router.example.com ssh: connect to host router.example.com port 22: Network is unreachable
Depending on your logging settings, search:
The
systemd
journal for the blocked packets:# journalctl -k -g "nft drop" Oct 14 17:27:18 router kernel: nft drop IN : IN=enp8s0 OUT= MAC=... SRC=198.51.100.5 DST=198.51.100.1 ... PROTO=TCP SPT=40464 DPT=22 ... SYN ...
The
/var/log/nftables.log
file for the blocked packets:Oct 14 17:27:18 router kernel: nft drop IN : IN=enp8s0 OUT= MAC=... SRC=198.51.100.5 DST=198.51.100.1 ... PROTO=TCP SPT=40464 DPT=22 ... SYN ...
41.8. Configuring port forwarding using nftables
Port forwarding enables administrators to forward packets sent to a specific destination port to a different local or remote port.
For example, if your web server does not have a public IP address, you can set a port forwarding rule on your firewall that forwards incoming packets on port 80
and 443
on the firewall to the web server. With this firewall rule, users on the internet can access the web server using the IP or host name of the firewall.
41.8.1. Forwarding incoming packets to a different local port
You can use nftables
to forward packets. For example, you can forward incoming IPv4 packets on port 8022
to port 22
on the local system.
Procedure
Create a table named
nat
with theip
address family:# nft add table ip nat
Add the
prerouting
andpostrouting
chains to the table:# nft -- add chain ip nat prerouting { type nat hook prerouting priority -100 \; }
NotePass the
--
option to thenft
command to prevent the shell from interpreting the negative priority value as an option of thenft
command.Add a rule to the
prerouting
chain that redirects incoming packets on port8022
to the local port22
:# nft add rule ip nat prerouting tcp dport 8022 redirect to :22
41.8.2. Forwarding incoming packets on a specific local port to a different host
You can use a destination network address translation (DNAT) rule to forward incoming packets on a local port to a remote host. This enables users on the internet to access a service that runs on a host with a private IP address.
For example, you can forward incoming IPv4 packets on the local port 443
to the same port number on the remote system with the 192.0.2.1
IP address.
Prerequisites
-
You are logged in as the
root
user on the system that should forward the packets.
Procedure
Create a table named
nat
with theip
address family:# nft add table ip nat
Add the
prerouting
andpostrouting
chains to the table:# nft -- add chain ip nat prerouting { type nat hook prerouting priority -100 \; } # nft add chain ip nat postrouting { type nat hook postrouting priority 100 \; }
NotePass the
--
option to thenft
command to prevent the shell from interpreting the negative priority value as an option of thenft
command.Add a rule to the
prerouting
chain that redirects incoming packets on port443
to the same port on192.0.2.1
:# nft add rule ip nat prerouting tcp dport 443 dnat to 192.0.2.1
Add a rule to the
postrouting
chain to masquerade outgoing traffic:# nft add rule ip nat postrouting daddr 192.0.2.1 masquerade
Enable packet forwarding:
# echo "net.ipv4.ip_forward=1" > /etc/sysctl.d/95-IPv4-forwarding.conf # sysctl -p /etc/sysctl.d/95-IPv4-forwarding.conf
41.9. Using nftables to limit the amount of connections
You can use nftables
to limit the number of connections or to block IP addresses that attempt to establish a given amount of connections to prevent them from using too many system resources.
41.9.1. Limiting the number of connections by using nftables
By using the ct count
parameter of the nft
utility, you can limit the number of simultaneous connections per IP address. For example, you can use this feature to configure that each source IP address can only establish two parallel SSH connections to a host.
Procedure
Create the
filter
table with theinet
address family:# nft add table inet filter
Add the
input
chain to theinet filter
table:# nft add chain inet filter input { type filter hook input priority 0 \; }
Create a dynamic set for IPv4 addresses:
# nft add set inet filter limit-ssh { type ipv4_addr\; flags dynamic \;}
Add a rule to the
input
chain that allows only two simultaneous incoming connections to the SSH port (22) from an IPv4 address and rejects all further connections from the same IP:# nft add rule inet filter input tcp dport ssh ct state new add @limit-ssh { ip saddr ct count over 2 } counter reject
Verification
- Establish more than two new simultaneous SSH connections from the same IP address to the host. Nftables refuses connections to the SSH port if two connections are already established.
Display the
limit-ssh
meter:# nft list set inet filter limit-ssh table inet filter { set limit-ssh { type ipv4_addr size 65535 flags dynamic elements = { 192.0.2.1 ct count over 2 , 192.0.2.2 ct count over 2 } } }
The
elements
entry displays addresses that currently match the rule. In this example,elements
lists IP addresses that have active connections to the SSH port. Note that the output does not display the number of active connections or if connections were rejected.
41.9.2. Blocking IP addresses that attempt more than ten new incoming TCP connections within one minute
You can temporarily block hosts that are establishing more than ten IPv4 TCP connections within one minute.
Procedure
Create the
filter
table with theip
address family:# nft add table ip filter
Add the
input
chain to thefilter
table:# nft add chain ip filter input { type filter hook input priority 0 \; }
Add a rule that drops all packets from source addresses that attempt to establish more than ten TCP connections within one minute:
# nft add rule ip filter input ip protocol tcp ct state new, untracked meter ratemeter { ip saddr timeout 5m limit rate over 10/minute } drop
The
timeout 5m
parameter defines thatnftables
automatically removes entries after five minutes to prevent that the meter fills up with stale entries.
Verification
To display the meter’s content, enter:
# nft list meter ip filter ratemeter table ip filter { meter ratemeter { type ipv4_addr size 65535 flags dynamic,timeout elements = { 192.0.2.1 limit rate over 10/minute timeout 5m expires 4m58s224ms } } }
41.10. Debugging nftables rules
The nftables
framework provides different options for administrators to debug rules and if packets match them.
41.10.1. Creating a rule with a counter
To identify if a rule is matched, you can use a counter.
- For more information about a procedure that adds a counter to an existing rule, see Adding a counter to an existing rule.
Prerequisites
- The chain to which you want to add the rule exists.
Procedure
Add a new rule with the
counter
parameter to the chain. The following example adds a rule with a counter that allows TCP traffic on port 22 and counts the packets and traffic that match this rule:# nft add rule inet example_table example_chain tcp dport 22 counter accept
To display the counter values:
# nft list ruleset table inet example_table { chain example_chain { type filter hook input priority filter; policy accept; tcp dport ssh counter packets 6872 bytes 105448565 accept } }
41.10.2. Adding a counter to an existing rule
To identify if a rule is matched, you can use a counter.
- For more information about a procedure that adds a new rule with a counter, see Creating a rule with the counter.
Prerequisites
- The rule to which you want to add the counter exists.
Procedure
Display the rules in the chain including their handles:
# nft --handle list chain inet example_table example_chain table inet example_table { chain example_chain { # handle 1 type filter hook input priority filter; policy accept; tcp dport ssh accept # handle 4 } }
Add the counter by replacing the rule but with the
counter
parameter. The following example replaces the rule displayed in the previous step and adds a counter:# nft replace rule inet example_table example_chain handle 4 tcp dport 22 counter accept
To display the counter values:
# nft list ruleset table inet example_table { chain example_chain { type filter hook input priority filter; policy accept; tcp dport ssh counter packets 6872 bytes 105448565 accept } }
41.10.3. Monitoring packets that match an existing rule
The tracing feature in nftables
in combination with the nft monitor
command enables administrators to display packets that match a rule. You can enable tracing for a rule an use it to monitoring packets that match this rule.
Prerequisites
- The rule to which you want to add the counter exists.
Procedure
Display the rules in the chain including their handles:
# nft --handle list chain inet example_table example_chain table inet example_table { chain example_chain { # handle 1 type filter hook input priority filter; policy accept; tcp dport ssh accept # handle 4 } }
Add the tracing feature by replacing the rule but with the
meta nftrace set 1
parameters. The following example replaces the rule displayed in the previous step and enables tracing:# nft replace rule inet example_table example_chain handle 4 tcp dport 22 meta nftrace set 1 accept
Use the
nft monitor
command to display the tracing. The following example filters the output of the command to display only entries that containinet example_table example_chain
:# nft monitor | grep "inet example_table example_chain" trace id 3c5eb15e inet example_table example_chain packet: iif "enp1s0" ether saddr 52:54:00:17:ff:e4 ether daddr 52:54:00:72:2f:6e ip saddr 192.0.2.1 ip daddr 192.0.2.2 ip dscp cs0 ip ecn not-ect ip ttl 64 ip id 49710 ip protocol tcp ip length 60 tcp sport 56728 tcp dport ssh tcp flags == syn tcp window 64240 trace id 3c5eb15e inet example_table example_chain rule tcp dport ssh nftrace set 1 accept (verdict accept) ...
WarningDepending on the number of rules with tracing enabled and the amount of matching traffic, the
nft monitor
command can display a lot of output. Usegrep
or other utilities to filter the output.
41.11. Backing up and restoring the nftables rule set
You can backup nftables
rules to a file and later restoring them. Also, administrators can use a file with the rules to, for example, transfer the rules to a different server.
41.11.1. Backing up the nftables rule set to a file
You can use the nft
utility to back up the nftables
rule set to a file.
Procedure
To backup
nftables
rules:In a format produced by
nft list ruleset
format:# nft list ruleset > file.nft
In JSON format:
# nft -j list ruleset > file.json
41.11.2. Restoring the nftables rule set from a file
You can restore the nftables
rule set from a file.
Procedure
To restore
nftables
rules:If the file to restore is in the format produced by
nft list ruleset
or containsnft
commands directly:# nft -f file.nft
If the file to restore is in JSON format:
# nft -j -f file.json
41.12. Additional resources
Chapter 42. Using xdp-filter for high-performance traffic filtering to prevent DDoS attacks
Compared to packet filters, such as nftables
, Express Data Path (XDP) processes and drops network packets right at the network interface. Therefore, XDP determines the next step for the package before it reaches a firewall or other applications. As a result, XDP filters require less resources and can process network packets at a much higher rate than conventional packet filters to defend against distributed denial of service (DDoS) attacks. For example, during testing, Red Hat dropped 26 million network packets per second on a single core, which is significantly higher than the drop rate of nftables
on the same hardware.
The xdp-filter
utility allows or drops incoming network packets using XDP. You can create rules to filter traffic to or from specific:
- IP addresses
- MAC addresses
- Ports
Note that, even if xdp-filter
has a significantly higher packet-processing rate, it does not have the same capabilities as, for example, nftables
. Consider xdp-filter
a conceptual utility to demonstrate packet filtering using XDP. Additionally, you can use the code of the utility for a better understanding of how to write your own XDP applications.
On other architectures than AMD and Intel 64-bit, the xdp-filter
utility is provided as a Technology Preview only. Technology Preview features are not supported with Red Hat production Service Level Agreements (SLAs), might not be functionally complete, and Red Hat does not recommend using them for production. These previews provide early access to upcoming product features, enabling customers to test functionality and provide feedback during the development process.
See Technology Preview Features Support Scope on the Red Hat Customer Portal for information about the support scope for Technology Preview features.
42.1. Dropping network packets that match an xdp-filter rule
You can use xdp-filter
to drop network packets:
- To a specific destination port
- From a specific IP address
- From a specific MAC address
The allow
policy of xdp-filter
defines that all traffic is allowed and the filter drops only network packets that match a particular rule. For example, use this method if you know the source IP addresses of packets you want to drop.
Prerequisites
-
The
xdp-tools
package is installed. - A network driver that supports XDP programs.
Procedure
Load
xdp-filter
to process incoming packets on a certain interface, such asenp1s0
:# xdp-filter load enp1s0
By default,
xdp-filter
uses theallow
policy, and the utility drops only traffic that matches any rule.Optionally, use the
-f feature
option to enable only particular features, such astcp
,ipv4
, orethernet
. Loading only the required features instead of all of them increases the speed of packet processing. To enable multiple features, separate them with a comma.If the command fails with an error, the network driver does not support XDP programs.
Add rules to drop packets that match them. For example:
To drop incoming packets to port
22
, enter:# xdp-filter port 22
This command adds a rule that matches TCP and UDP traffic. To match only a particular protocol, use the
-p protocol
option.To drop incoming packets from
192.0.2.1
, enter:# xdp-filter ip 192.0.2.1 -m src
Note that
xdp-filter
does not support IP ranges.To drop incoming packets from MAC address
00:53:00:AA:07:BE
, enter:# xdp-filter ether 00:53:00:AA:07:BE -m src
Verification
Use the following command to display statistics about dropped and allowed packets:
# xdp-filter status
Additional resources
-
xdp-filter(8)
man page -
If you are a developer and interested in the code of
xdp-filter
, download and install the corresponding source RPM (SRPM) from the Red Hat Customer Portal.
42.2. Dropping all network packets except the ones that match an xdp-filter rule
You can use xdp-filter
to allow only network packets:
- From and to a specific destination port
- From and to a specific IP address
- From and to specific MAC address
To do so, use the deny
policy of xdp-filter
which defines that the filter drops all network packets except the ones that match a particular rule. For example, use this method if you do not know the source IP addresses of packets you want to drop.
If you set the default policy to deny
when you load xdp-filter
on an interface, the kernel immediately drops all packets from this interface until you create rules that allow certain traffic. To avoid being locked out from the system, enter the commands locally or connect through a different network interface to the host.
Prerequisites
-
The
xdp-tools
package is installed. - You are logged in to the host either locally or using a network interface for which you do not plan to filter the traffic.
- A network driver that supports XDP programs.
Procedure
Load
xdp-filter
to process packets on a certain interface, such asenp1s0
:# xdp-filter load enp1s0 -p deny
Optionally, use the
-f feature
option to enable only particular features, such astcp
,ipv4
, orethernet
. Loading only the required features instead of all of them increases the speed of packet processing. To enable multiple features, separate them with a comma.If the command fails with an error, the network driver does not support XDP programs.
Add rules to allow packets that match them. For example:
To allow packets to port
22
, enter:# xdp-filter port 22
This command adds a rule that matches TCP and UDP traffic. To match only a particular protocol, pass the
-p protocol
option to the command.To allow packets to
192.0.2.1
, enter:# xdp-filter ip 192.0.2.1
Note that
xdp-filter
does not support IP ranges.To allow packets to MAC address
00:53:00:AA:07:BE
, enter:# xdp-filter ether 00:53:00:AA:07:BE
ImportantThe
xdp-filter
utility does not support stateful packet inspection. This requires that you either do not set a mode using the-m mode
option or you add explicit rules to allow incoming traffic that the machine receives in reply to outgoing traffic.
Verification
Use the following command to display statistics about dropped and allowed packets:
# xdp-filter status
Additional resources
-
xdp-filter(8)
man page. -
If you are a developer and you are interested in the code of
xdp-filter
, download and install the corresponding source RPM (SRPM) from the Red Hat Customer Portal.
Chapter 43. Capturing network packets
To debug network issues and communications, you can capture network packets. The following sections provide instructions and additional information about capturing network packets.
43.1. Using xdpdump to capture network packets including packets dropped by XDP programs
The xdpdump
utility captures network packets. Unlike the tcpdump
utility, xdpdump
uses an extended Berkeley Packet Filter(eBPF) program for this task. This enables xdpdump
to also capture packets dropped by Express Data Path (XDP) programs. User-space utilities, such as tcpdump
, are not able to capture these dropped packages, as well as original packets modified by an XDP program.
You can use xdpdump
to debug XDP programs that are already attached to an interface. Therefore, the utility can capture packets before an XDP program is started and after it has finished. In the latter case, xdpdump
also captures the XDP action. By default, xdpdump
captures incoming packets at the entry of the XDP program.
On other architectures than AMD and Intel 64-bit, the xdpdump
utility is provided as a Technology Preview only. Technology Preview features are not supported with Red Hat production Service Level Agreements (SLAs), might not be functionally complete, and Red Hat does not recommend using them for production. These previews provide early access to upcoming product features, enabling customers to test functionality and provide feedback during the development process.
See Technology Preview Features Support Scope on the Red Hat Customer Portal for information about the support scope for Technology Preview features.
Note that xdpdump
has no packet filter or decode capabilities. However, you can use it in combination with tcpdump
for packet decoding.
Prerequisites
- A network driver that supports XDP programs.
-
An XDP program is loaded to the
enp1s0
interface. If no program is loaded,xdpdump
captures packets in a similar waytcpdump
does, for backward compatibility.
Procedure
To capture packets on the
enp1s0
interface and write them to the/root/capture.pcap
file, enter:# xdpdump -i enp1s0 -w /root/capture.pcap
- To stop capturing packets, press Ctrl+C.
Additional resources
-
xdpdump(8)
man page -
If you are a developer and you are interested in the source code of
xdpdump
, download and install the corresponding source RPM (SRPM) from the Red Hat Customer Portal.
43.2. Additional resources
Chapter 44. Understanding the eBPF networking features in RHEL 8
The extended Berkeley Packet Filter (eBPF) is an in-kernel virtual machine that allows code execution in the kernel space. This code runs in a restricted sandbox environment with access only to a limited set of functions.
In networking, you can use eBPF to complement or replace kernel packet processing. Depending on the hook you use, eBPF programs have, for example:
- Read and write access to packet data and metadata
- Can look up sockets and routes
- Can set socket options
- Can redirect packets
44.1. Overview of networking eBPF features in RHEL 8
You can attach extended Berkeley Packet Filter (eBPF) networking programs to the following hooks in RHEL:
- eXpress Data Path (XDP): Provides early access to received packets before the kernel networking stack processes them.
-
tc
eBPF classifier with direct-action flag: Provides powerful packet processing on ingress and egress. - Control Groups version 2 (cgroup v2): Enables filtering and overriding socket-based operations performed by programs in a control group.
- Socket filtering: Enables filtering of packets received from sockets. This feature was also available in the classic Berkeley Packet Filter (cBPF), but has been extended to support eBPF programs.
- Stream parser: Enables splitting up streams to individual messages, filtering, and redirecting them to sockets.
-
SO_REUSEPORT
socket selection: Provides a programmable selection of a receiving socket from areuseport
socket group. - Flow dissector: Enables overriding the way the kernel parses packet headers in certain situations.
- TCP congestion control callbacks: Enables implementing a custom TCP congestion control algorithm.
- Routes with encapsulation: Enables creating custom tunnel encapsulation.
Note that Red Hat does not support all of the eBPF functionality that is available in RHEL and described here. For further details and the support status of the individual hooks, see the RHEL 8 Release Notes and the following overview.
XDP
You can attach programs of the BPF_PROG_TYPE_XDP
type to a network interface. The kernel then executes the program on received packets before the kernel network stack starts processing them. This allows fast packet forwarding in certain situations, such as fast packet dropping to prevent distributed denial of service (DDoS) attacks and fast packet redirects for load balancing scenarios.
You can also use XDP for different forms of packet monitoring and sampling. The kernel allows XDP programs to modify packets and to pass them for further processing to the kernel network stack.
The following XDP modes are available:
- Native (driver) XDP: The kernel executes the program from the earliest possible point during packet reception. At this moment, the kernel did not parse the packet and, therefore, no metadata provided by the kernel is available. This mode requires that the network interface driver supports XDP but not all drivers support this native mode.
- Generic XDP: The kernel network stack executes the XDP program early in the processing. At that time, kernel data structures have been allocated, and the packet has been pre-processed. If a packet should be dropped or redirected, it requires a significant overhead compared to the native mode. However, the generic mode does not require network interface driver support and works with all network interfaces.
- Offloaded XDP: The kernel executes the XDP program on the network interface instead of on the host CPU. Note that this requires specific hardware, and only certain eBPF features are available in this mode.
On RHEL, load all XDP programs using the libxdp
library. This library enables system-controlled usage of XDP.
Currently, there are some system configuration limitations for XDP programs. For example, you must disable certain hardware offload features on the receiving interface. Additionally, not all features are available with all drivers that support the native mode.
In RHEL 8.7, Red Hat supports the XDP feature only if all of the following conditions apply:
- You load the XDP program on an AMD or Intel 64-bit architecture.
-
You use the
libxdp
library to load the program into the kernel. - The XDP program does not use the XDP hardware offloading.
Additionally, Red Hat provides the following usage of XDP features as unsupported Technology Preview:
-
Loading XDP programs on architectures other than AMD and Intel 64-bit. Note that the
libxdp
library is not available for architectures other than AMD and Intel 64-bit. - The XDP hardware offloading.
AF_XDP
Using an XDP program that filters and redirects packets to a given AF_XDP
socket, you can use one or more sockets from the AF_XDP
protocol family to quickly copy packets from the kernel to the user space.
In RHEL 8.7, Red Hat provides this feature as an unsupported Technology Preview.
Traffic Control
The Traffic Control (tc
) subsystem offers the following types of eBPF programs:
-
BPF_PROG_TYPE_SCHED_CLS
-
BPF_PROG_TYPE_SCHED_ACT
These types enable you to write custom tc
classifiers and tc
actions in eBPF. Together with the parts of the tc
ecosystem, this provides the ability for powerful packet processing and is the core part of several container networking orchestration solutions.
In most cases, only the classifier is used, as with the direct-action flag, the eBPF classifier can execute actions directly from the same eBPF program. The clsact
Queueing Discipline (qdisc
) has been designed to enable this on the ingress side.
Note that using a flow dissector eBPF program can influence operation of some other qdiscs
and tc
classifiers, such as flower
.
The eBPF for tc
feature is fully supported in RHEL 8.2 and later.
Socket filter
Several utilities use or have used the classic Berkeley Packet Filter (cBPF) for filtering packets received on a socket. For example, the tcpdump
utility enables the user to specify expressions, which tcpdump
then translates into cBPF code.
As an alternative to cBPF, the kernel allows eBPF programs of the BPF_PROG_TYPE_SOCKET_FILTER
type for the same purpose.
In RHEL 8.7, Red Hat provides this feature as an unsupported Technology Preview.
Control Groups
In RHEL, you can use multiple types of eBPF programs that you can attach to a cgroup. The kernel executes these programs when a program in the given cgroup performs an operation. Note that you can use only cgroups version 2.
The following networking-related cgroup eBPF programs are available in RHEL:
-
BPF_PROG_TYPE_SOCK_OPS
: The kernel calls this program on various TCP events. The program can adjust the behavior of the kernel TCP stack, including custom TCP header options, and so on. -
BPF_PROG_TYPE_CGROUP_SOCK_ADDR
: The kernel calls this program duringconnect
,bind
,sendto
,recvmsg
,getpeername
, andgetsockname
operations. This program allows changing IP addresses and ports. This is useful when you implement socket-based network address translation (NAT) in eBPF. -
BPF_PROG_TYPE_CGROUP_SOCKOPT
: The kernel calls this program duringsetsockopt
andgetsockopt
operations and allows changing the options. -
BPF_PROG_TYPE_CGROUP_SOCK
: The kernel calls this program during socket creation, socket releasing, and binding to addresses. You can use these programs to allow or deny the operation, or only to inspect socket creation for statistics. -
BPF_PROG_TYPE_CGROUP_SKB
: This program filters individual packets on ingress and egress, and can accept or reject packets. -
BPF_PROG_TYPE_CGROUP_SYSCTL
: This program allows filtering of access to system controls (sysctl
). -
BPF_CGROUP_INET4_GETPEERNAME
,BPF_CGROUP_INET6_GETPEERNAME
,BPF_CGROUP_INET4_GETSOCKNAME
, andBPF_CGROUP_INET6_GETSOCKNAME
: Using these programs, you can override the result ofgetsockname
andgetpeername
system calls. This is useful when you implement socket-based network address translation (NAT) in eBPF.
In RHEL 8.7, Red Hat provides this feature as an unsupported Technology Preview.
Stream Parser
A stream parser operates on a group of sockets that are added to a special eBPF map. The eBPF program then processes packets that the kernel receives or sends on those sockets.
The following stream parser eBPF programs are available in RHEL:
-
BPF_PROG_TYPE_SK_SKB
: An eBPF program parses packets received from the socket into individual messages, and instructs the kernel to drop those messages or send them to another socket in the group. -
BPF_PROG_TYPE_SK_MSG
: This program filters egress messages. An eBPF program parses the packets into individual messages and either approves or rejects them.
In RHEL 8.7, Red Hat provides this feature as an unsupported Technology Preview.
SO_REUSEPORT socket selection
Using this socket option, you can bind multiple sockets to the same IP address and port. Without eBPF, the kernel selects the receiving socket based on a connection hash. With the BPF_PROG_TYPE_SK_REUSEPORT
program, the selection of the receiving socket is fully programmable.
In RHEL 8.7, Red Hat provides this feature as an unsupported Technology Preview.
Flow dissector
When the kernel needs to process packet headers without going through the full protocol decode, they are dissected
. For example, this happens in the tc
subsystem, in multipath routing, in bonding, or when calculating a packet hash. In this situation the kernel parses the packet headers and fills internal structures with the information from the packet headers. You can replace this internal parsing using the BPF_PROG_TYPE_FLOW_DISSECTOR
program. Note that you can only dissect TCP and UDP over IPv4 and IPv6 in eBPF in RHEL.
In RHEL 8.7, Red Hat provides this feature as an unsupported Technology Preview.
TCP Congestion Control
You can write a custom TCP congestion control algorithm using a group of BPF_PROG_TYPE_STRUCT_OPS
programs that implement struct tcp_congestion_oops
callbacks. An algorithm that is implemented this way is available to the system alongside the built-in kernel algorithms.
In RHEL 8.7, Red Hat provides this feature as an unsupported Technology Preview.
Routes with encapsulation
You can attach one of the following eBPF program types to routes in the routing table as a tunnel encapsulation attribute:
-
BPF_PROG_TYPE_LWT_IN
-
BPF_PROG_TYPE_LWT_OUT
-
BPF_PROG_TYPE_LWT_XMIT
The functionality of such an eBPF program is limited to specific tunnel configurations and does not allow creating a generic encapsulation or decapsulation solution.
In RHEL 8.7, Red Hat provides this feature as an unsupported Technology Preview.
Socket lookup
To bypass limitations of the bind
system call, use an eBPF program of the BPF_PROG_TYPE_SK_LOOKUP
type. Such programs can select a listening socket for new incoming TCP connections or an unconnected socket for UDP packets.
In RHEL 8.7, Red Hat provides this feature as an unsupported Technology Preview.
44.2. Overview of XDP features in RHEL 8 by network cards
The following is an overview of XDP-enabled network cards and the XDP features you can use with them:
Network card | Driver | Basic | Redirect | Target | HW offload | Zero-copy |
---|---|---|---|---|---|---|
Amazon Elastic Network Adapter |
| yes | yes | yes [a] | no | no |
Broadcom NetXtreme-C/E 10/25/40/50 gigabit Ethernet |
| yes | yes | yes [a] | no | no |
Cavium Thunder Virtual function |
| yes | no | no | no | no |
Google Virtual NIC (gVNIC) support |
| yes | yes | yes | no | yes |
Intel® 10GbE PCI Express Virtual Function Ethernet |
| yes | no | no | no | no |
Intel® 10GbE PCI Express adapters |
| yes | yes | yes [a] | no | yes |
Intel® Ethernet Connection E800 Series |
| yes | yes | yes [a] | no | yes |
Intel® Ethernet Controller I225-LM/I225-V family |
| yes | yes | yes | no | yes |
Intel® Ethernet Controller XL710 Family |
| yes | yes | no | yes | |
Intel® PCI Express Gigabit adapters |
| yes | yes | yes [a] | no | no |
Mellanox 5th generation network adapters (ConnectX series) |
| yes | yes | yes [b] | no | yes |
Mellanox Technologies 1/10/40Gbit Ethernet |
| yes | yes | no | no | no |
Microsoft Azure Network Adapter |
| yes | yes | yes | no | no |
Microsoft Hyper-V virtual network |
| yes | yes | yes | no | no |
Netronome® NFP4000/NFP6000 NIC |
| yes | no | no | yes | no |
QEMU Virtio network |
| yes | yes | yes [a] | no | no |
QLogic QED 25/40/100Gb Ethernet NIC |
| yes | yes | yes | no | no |
Solarflare SFC9000/SFC9100/EF100-family |
| yes | yes | yes [b] | no | no |
Universal TUN/TAP device |
| yes | yes | yes | no | no |
Virtual Ethernet pair device |
| yes | yes | yes | no | no |
[a]
Only if an XDP program is loaded on the interface.
[b]
Requires several XDP TX queues allocated that is larger or equal to the largest CPU index.
|
Legend:
-
Basic: Supports basic return codes:
DROP
,PASS
,ABORTED
, andTX
. -
Redirect: Supports the
REDIRECT
return code. -
Target: Can be a target of a
REDIRECT
return code. - HW offload: Supports XDP hardware offload.
-
Zero-copy: Supports the zero-copy mode for the
AF_XDP
protocol family.
Chapter 45. Network tracing using the BPF compiler collection
BPF Compiler Collection (BCC) is a library, which facilitates the creation of the extended Berkeley Packet Filter (eBPF) programs. The main utility of eBPF programs is analyzing the operating system performance and network performance without experiencing overhead or security issues.
BCC removes the need for users to know deep technical details of eBPF, and provides many out-of-the-box starting points, such as the bcc-tools
package with pre-created eBPF programs.
The eBPF programs are triggered on events, such as disk I/O, TCP connections, and process creations. It is unlikely that the programs should cause the kernel to crash, loop or become unresponsive because they run in a safe virtual machine in the kernel.
45.1. Installing the bcc-tools package
Install the bcc-tools
package, which also installs the BPF Compiler Collection (BCC) library as a dependency.
Procedure
Install
bcc-tools
.#
yum install bcc-tools
The BCC tools are installed in the
/usr/share/bcc/tools/
directory.
Verification
Inspect the installed tools:
#
ll /usr/share/bcc/tools/
... -rwxr-xr-x. 1 root root 4198 Dec 14 17:53 dcsnoop -rwxr-xr-x. 1 root root 3931 Dec 14 17:53 dcstat -rwxr-xr-x. 1 root root 20040 Dec 14 17:53 deadlock_detector -rw-r--r--. 1 root root 7105 Dec 14 17:53 deadlock_detector.c drwxr-xr-x. 3 root root 8192 Mar 11 10:28 doc -rwxr-xr-x. 1 root root 7588 Dec 14 17:53 execsnoop -rwxr-xr-x. 1 root root 6373 Dec 14 17:53 ext4dist -rwxr-xr-x. 1 root root 10401 Dec 14 17:53 ext4slower ...The
doc
directory in the listing above contains documentation for each tool.
45.2. Displaying TCP connections added to the Kernel’s accept queue
After the kernel receives the ACK
packet in a TCP 3-way handshake, the kernel moves the connection from the SYN
queue to the accept
queue after the connection’s state changes to ESTABLISHED
. Therefore, only successful TCP connections are visible in this queue.
The tcpaccept
utility uses eBPF features to display all connections the kernel adds to the accept
queue. The utility is lightweight because it traces the accept()
function of the kernel instead of capturing packets and filtering them. For example, use tcpaccept
for general troubleshooting to display new connections the server has accepted.
Procedure
Enter the following command to start the tracing the kernel
accept
queue:# /usr/share/bcc/tools/tcpaccept PID COMM IP RADDR RPORT LADDR LPORT 843 sshd 4 192.0.2.17 50598 192.0.2.1 22 1107 ns-slapd 4 198.51.100.6 38772 192.0.2.1 389 1107 ns-slapd 4 203.0.113.85 38774 192.0.2.1 389 ...
Each time the kernel accepts a connection,
tcpaccept
displays the details of the connections.- Press Ctrl+C to stop the tracing process.
Additional resources
-
tcpaccept(8)
man page -
/usr/share/bcc/tools/doc/tcpaccept_example.txt
file
45.3. Tracing outgoing TCP connection attempts
The tcpconnect
utility uses eBPF features to trace outgoing TCP connection attempts. The output of the utility also includes connections that failed.
The tcpconnect
utility is lightweight because it traces, for example, the connect()
function of the kernel instead of capturing packets and filtering them.
Procedure
Enter the following command to start the tracing process that displays all outgoing connections:
# /usr/share/bcc/tools/tcpconnect PID COMM IP SADDR DADDR DPORT 31346 curl 4 192.0.2.1 198.51.100.16 80 31348 telnet 4 192.0.2.1 203.0.113.231 23 31361 isc-worker00 4 192.0.2.1 192.0.2.254 53 ...
Each time the kernel processes an outgoing connection,
tcpconnect
displays the details of the connections.- Press Ctrl+C to stop the tracing process.
Additional resources
-
tcpconnect(8)
man page -
/usr/share/bcc/tools/doc/tcpconnect_example.txt
file
45.4. Measuring the latency of outgoing TCP connections
The TCP connection latency is the time taken to establish a connection. This typically involves the kernel TCP/IP processing and network round trip time, and not the application runtime.
The tcpconnlat
utility uses eBPF features to measure the time between a sent SYN
packet and the received response packet.
Procedure
Start measuring the latency of outgoing connections:
# /usr/share/bcc/tools/tcpconnlat PID COMM IP SADDR DADDR DPORT LAT(ms) 32151 isc-worker00 4 192.0.2.1 192.0.2.254 53 0.60 32155 ssh 4 192.0.2.1 203.0.113.190 22 26.34 32319 curl 4 192.0.2.1 198.51.100.59 443 188.96 ...
Each time the kernel processes an outgoing connection,
tcpconnlat
displays the details of the connection after the kernel receives the response packet.- Press Ctrl+C to stop the tracing process.
Additional resources
-
tcpconnlat(8)
man page -
/usr/share/bcc/tools/doc/tcpconnlat_example.txt
file
45.5. Displaying details about TCP packets and segments that were dropped by the kernel
The tcpdrop
utility enables administrators to display details about TCP packets and segments that were dropped by the kernel. Use this utility to debug high rates of dropped packets that can cause the remote system to send timer-based retransmits. High rates of dropped packets and segments can impact the performance of a server.
Instead of capturing and filtering packets, which is resource-intensive, the tcpdrop
utility uses eBPF features to retrieve the information directly from the kernel.
Procedure
Enter the following command to start displaying details about dropped TCP packets and segments:
# /usr/share/bcc/tools/tcpdrop TIME PID IP SADDR:SPORT > DADDR:DPORT STATE (FLAGS) 13:28:39 32253 4 192.0.2.85:51616 > 192.0.2.1:22 CLOSE_WAIT (FIN|ACK) b'tcp_drop+0x1' b'tcp_data_queue+0x2b9' ... 13:28:39 1 4 192.0.2.85:51616 > 192.0.2.1:22 CLOSE (ACK) b'tcp_drop+0x1' b'tcp_rcv_state_process+0xe2' ...
Each time the kernel drops TCP packets and segments,
tcpdrop
displays the details of the connection, including the kernel stack trace that led to the dropped package.- Press Ctrl+C to stop the tracing process.
Additional resources
-
tcpdrop(8)
man page -
/usr/share/bcc/tools/doc/tcpdrop_example.txt
file
45.6. Tracing TCP sessions
The tcplife
utility uses eBPF to trace TCP sessions that open and close, and prints a line of output to summarize each one. Administrators can use tcplife
to identify connections and the amount of transferred traffic.
For example, you can display connections to port 22
(SSH) to retrieve the following information:
- The local process ID (PID)
- The local process name
- The local IP address and port number
- The remote IP address and port number
- The amount of received and transmitted traffic in KB.
- The time in milliseconds the connection was active
Procedure
Enter the following command to start the tracing of connections to the local port
22
:/usr/share/bcc/tools/tcplife -L 22 PID COMM LADDR LPORT RADDR RPORT TX_KB RX_KB MS 19392 sshd 192.0.2.1 22 192.0.2.17 43892 53 52 6681.95 19431 sshd 192.0.2.1 22 192.0.2.245 43902 81 249381 7585.09 19487 sshd 192.0.2.1 22 192.0.2.121 43970 6998 7 16740.35 ...
Each time a connection is closed,
tcplife
displays the details of the connections.- Press Ctrl+C to stop the tracing process.
Additional resources
-
tcplife(8)
man page -
/usr/share/bcc/tools/doc/tcplife_example.txt
file
45.7. Tracing TCP retransmissions
The tcpretrans
utility displays details about TCP retransmissions, such as the local and remote IP address and port number, as well as the TCP state at the time of the retransmissions.
The utility uses eBPF features and, therefore, has a very low overhead.
Procedure
Use the following command to start displaying TCP retransmission details:
# /usr/share/bcc/tools/tcpretrans TIME PID IP LADDR:LPORT T> RADDR:RPORT STATE 00:23:02 0 4 192.0.2.1:22 R> 198.51.100.0:26788 ESTABLISHED 00:23:02 0 4 192.0.2.1:22 R> 198.51.100.0:26788 ESTABLISHED 00:45:43 0 4 192.0.2.1:22 R> 198.51.100.0:17634 ESTABLISHED ...
Each time the kernel calls the TCP retransmit function,
tcpretrans
displays the details of the connection.- Press Ctrl+C to stop the tracing process.
Additional resources
-
tcpretrans(8)
man page -
/usr/share/bcc/tools/doc/tcpretrans_example.txt
file
45.8. Displaying TCP state change information
During a TCP session, the TCP state changes. The tcpstates
utility uses eBPF functions to trace these state changes, and prints details including the duration in each state. For example, use tcpstates
to identify if connections spend too much time in the initialization state.
Procedure
Use the following command to start tracing TCP state changes:
# /usr/share/bcc/tools/tcpstates SKADDR C-PID C-COMM LADDR LPORT RADDR RPORT OLDSTATE -> NEWSTATE MS ffff9cd377b3af80 0 swapper/1 0.0.0.0 22 0.0.0.0 0 LISTEN -> SYN_RECV 0.000 ffff9cd377b3af80 0 swapper/1 192.0.2.1 22 192.0.2.45 53152 SYN_RECV -> ESTABLISHED 0.067 ffff9cd377b3af80 818 sssd_nss 192.0.2.1 22 192.0.2.45 53152 ESTABLISHED -> CLOSE_WAIT 65636.773 ffff9cd377b3af80 1432 sshd 192.0.2.1 22 192.0.2.45 53152 CLOSE_WAIT -> LAST_ACK 24.409 ffff9cd377b3af80 1267 pulseaudio 192.0.2.1 22 192.0.2.45 53152 LAST_ACK -> CLOSE 0.376 ...
Each time a connection changes its state,
tcpstates
displays a new line with updated connection details.If multiple connections change their state at the same time, use the socket address in the first column (
SKADDR
) to determine which entries belong to the same connection.- Press Ctrl+C to stop the tracing process.
Additional resources
-
tcpstates(8)
man page -
/usr/share/bcc/tools/doc/tcpstates_example.txt
file
45.9. Summarizing and aggregating TCP traffic sent to specific subnets
The tcpsubnet
utility summarizes and aggregates IPv4 TCP traffic that the local host sends to subnets and displays the output on a fixed interval. The utility uses eBPF features to collect and summarize the data to reduce the overhead.
By default, tcpsubnet
summarizes traffic for the following subnets:
-
127.0.0.1/32
-
10.0.0.0/8
-
172.16.0.0/12
-
192.0.2.0/24/16
-
0.0.0.0/0
Note that the last subnet (0.0.0.0/0
) is a catch-all option. The tcpsubnet
utility counts all traffic for subnets different than the first four in this catch-all entry.
Follow the procedure to count the traffic for the 192.0.2.0/24
and 198.51.100.0/24
subnets. Traffic to other subnets will be tracked in the 0.0.0.0/0
catch-all subnet entry.
Procedure
Start monitoring the amount of traffic send to the
192.0.2.0/24
,198.51.100.0/24
, and other subnets:# /usr/share/bcc/tools/tcpsubnet 192.0.2.0/24,198.51.100.0/24,0.0.0.0/0 Tracing... Output every 1 secs. Hit Ctrl-C to end [02/21/20 10:04:50] 192.0.2.0/24 856 198.51.100.0/24 7467 [02/21/20 10:04:51] 192.0.2.0/24 1200 198.51.100.0/24 8763 0.0.0.0/0 673 ...
This command displays the traffic in bytes for the specified subnets once per second.
- Press Ctrl+C to stop the tracing process.
Additional resources
-
tcpsubnet(8)
man page -
/usr/share/bcc/tools/doc/tcpsubnet.txt
file
45.10. Displaying the network throughput by IP address and port
The tcptop
utility displays TCP traffic the host sends and receives in kilobytes. The report automatically refreshes and contains only active TCP connections. The utility uses eBPF features and, therefore, has only a very low overhead.
Procedure
To monitor the sent and received traffic, enter:
# /usr/share/bcc/tools/tcptop 13:46:29 loadavg: 0.10 0.03 0.01 1/215 3875 PID COMM LADDR RADDR RX_KB TX_KB 3853 3853 192.0.2.1:22 192.0.2.165:41838 32 102626 1285 sshd 192.0.2.1:22 192.0.2.45:39240 0 0 ...
The output of the command includes only active TCP connections. If the local or remote system closes a connection, the connection is no longer visible in the output.
- Press Ctrl+C to stop the tracing process.
Additional resources
-
tcptop(8)
man page -
/usr/share/bcc/tools/doc/tcptop.txt
file
45.11. Tracing established TCP connections
The tcptracer
utility traces the kernel functions that connect, accept, and close TCP connections. The utility uses eBPF features and, therefore, has a very low overhead.
Procedure
Use the following command to start the tracing process:
# /usr/share/bcc/tools/tcptracer Tracing TCP established connections. Ctrl-C to end. T PID COMM IP SADDR DADDR SPORT DPORT A 1088 ns-slapd 4 192.0.2.153 192.0.2.1 0 65535 A 845 sshd 4 192.0.2.1 192.0.2.67 22 42302 X 4502 sshd 4 192.0.2.1 192.0.2.67 22 42302 ...
Each time the kernel connects, accepts, or closes a connection,
tcptracer
displays the details of the connections.- Press Ctrl+C to stop the tracing process.
Additional resources
-
tcptracer(8)
man page -
/usr/share/bcc/tools/doc/tcptracer_example.txt
file
45.12. Tracing IPv4 and IPv6 listen attempts
The solisten
utility traces all IPv4 and IPv6 listen attempts. It traces the listen attempts including that ultimately fail or the listening program that does not accept the connection. The utility traces function that the kernel calls when a program wants to listen for TCP connections.
Procedure
Enter the following command to start the tracing process that displays all listen TCP attempts:
# /usr/share/bcc/tools/solisten PID COMM PROTO BACKLOG PORT ADDR 3643 nc TCPv4 1 4242 0.0.0.0 3659 nc TCPv6 1 4242 2001:db8:1::1 4221 redis-server TCPv6 128 6379 :: 4221 redis-server TCPv4 128 6379 0.0.0.0 ....
- Press Ctrl+C to stop the tracing process.
Additional resources
-
solisten(9)
man page -
/usr/share/bcc/tools/doc/solisten_example.txt
file
45.13. Summarizing the service time of soft interrupts
The softirqs
utility summarizes the time spent servicing soft interrupts (soft IRQs) and shows this time as either totals or histogram distributions. This utility uses the irq:softirq_enter
and irq:softirq_exit
kernel tracepoints, which is a stable tracing mechanism.
Procedure
Enter the following command to start the tracing
soft irq
event time:# /usr/share/bcc/tools/softirqs Tracing soft irq event time... Hit Ctrl-C to end. ^C SOFTIRQ TOTAL_usecs tasklet 166 block 9152 net_rx 12829 rcu 53140 sched 182360 timer 306256
- Press Ctrl+C to stop the tracing process.
Additional resources
-
softirqs(8)
man page -
/usr/share/bcc/tools/doc/softirqs_example.txt
file -
mpstat(1)
man page
45.14. Summarizing packets size and count on a network interface
The netqtop
utility displays statistics about the attributes of received (RX) and transmitted (TX) packets on each network queue of a particular network interface. The statistics include:
- Bytes per second (BPS)
- Packets per second (PPS)
- The average packet size
- Total number of packets
To generate these statistics, netqtop
traces the kernel functions that perform events of transmitted packets net_dev_start_xmit
and received packets netif_receive_skb
.
Procedure
Display the number of packets within the range of bytes size of the time interval of
2
seconds:# /usr/share/bcc/tools/netqtop -n enp1s0 -i 2 Fri Jan 31 18:08:55 2023 TX QueueID avg_size [0, 64) [64, 512) [512, 2K) [2K, 16K) [16K, 64K) 0 0 0 0 0 0 0 Total 0 0 0 0 0 0 RX QueueID avg_size [0, 64) [64, 512) [512, 2K) [2K, 16K) [16K, 64K) 0 38.0 1 0 0 0 0 Total 38.0 1 0 0 0 0 ----------------------------------------------------------------------------- Fri Jan 31 18:08:57 2023 TX QueueID avg_size [0, 64) [64, 512) [512, 2K) [2K, 16K) [16K, 64K) 0 0 0 0 0 0 0 Total 0 0 0 0 0 0 RX QueueID avg_size [0, 64) [64, 512) [512, 2K) [2K, 16K) [16K, 64K) 0 38.0 1 0 0 0 0 Total 38.0 1 0 0 0 0 -----------------------------------------------------------------------------
-
Press Ctrl+C to stop
netqtop
.
Additional resources
-
netqtop(8)
man page -
/usr/share/bcc/tools/doc/netqtop_example.txt
45.15. Additional resources
-
/usr/share/doc/bcc/README.md
Chapter 46. Configuring network devices to accept traffic from all MAC addresses
Network devices usually intercept and read packets that their controller is programmed to receive. You can configure the network devices to accept traffic from all MAC addresses in a virtual switch or at the port group level.
You can use this network mode to:
- Diagnose network connectivity issues
- Monitor network activity for security reasons
- Intercept private data-in-transit or intrusion in the network
You can enable this mode for any kind of network device, except InfiniBand
.
46.1. Temporarily configuring a device to accept all traffic
You can use the ip
utility to temporary configure a network device to accept all traffic regardless of the MAC addresses.
Procedure
Optional: Display the network interfaces to identify the one for which you want to receive all traffic:
# ip address show 1: enp1s0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc fq_codel state DOWN group default qlen 1000 link/ether 98:fa:9b:a4:34:09 brd ff:ff:ff:ff:ff:ff ...
Modify the device to enable or disable this property:
To enable the
accept-all-mac-addresses
mode forenp1s0
:# ip link set enp1s0 promisc on
To disable the
accept-all-mac-addresses
mode forenp1s0
:# ip link set enp1s0 promisc off
Verification
Verify that the
accept-all-mac-addresses
mode is enabled:# ip link show enp1s0 1: enp1s0: <NO-CARRIER,BROADCAST,MULTICAST,PROMISC,UP> mtu 1500 qdisc fq_codel state DOWN mode DEFAULT group default qlen 1000 link/ether 98:fa:9b:a4:34:09 brd ff:ff:ff:ff:ff:ff
The
PROMISC
flag in the device description indicates that the mode is enabled.
46.2. Permanently configuring a network device to accept all traffic using nmcli
You can use the nmcli
utility to permanently configure a network device to accept all traffic regardless of the MAC addresses.
Procedure
Optional: Display the network interfaces to identify the one for which you want to receive all traffic:
# ip address show 1: enp1s0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc fq_codel state DOWN group default qlen 1000 link/ether 98:fa:9b:a4:34:09 brd ff:ff:ff:ff:ff:ff ...
You can create a new connection, if you do not have any.
Modify the network device to enable or disable this property.
To enable the
ethernet.accept-all-mac-addresses
mode forenp1s0
:# nmcli connection modify enp1s0 ethernet.accept-all-mac-addresses yes
To disable the
accept-all-mac-addresses
mode forenp1s0
:# nmcli connection modify enp1s0 ethernet.accept-all-mac-addresses no
Apply the changes, reactivate the connection:
# nmcli connection up enp1s0
Verification
Verify that the
ethernet.accept-all-mac-addresses
mode is enabled:# nmcli connection show enp1s0 ... 802-3-ethernet.accept-all-mac-addresses:1 (true)
The
802-3-ethernet.accept-all-mac-addresses: true
indicates that the mode is enabled.
46.3. Permanently configuring a network device to accept all traffic using nmstatectl
Use the nmstatectl
utility to configure a device to accept all traffic regardless of the MAC addresses through the Nmstate API. The Nmstate API ensures that, after setting the configuration, the result matches the configuration file. If anything fails, nmstatectl
automatically rolls back the changes to avoid leaving the system in an incorrect state.
Prerequisites
-
The
nmstate
package is installed. -
The
enp1s0.yml
file that you used to configure the device is available.
Procedure
Edit the existing
enp1s0.yml
file for theenp1s0
connection and add the following content to it:--- interfaces: - name: enp1s0 type: ethernet state: up accept -all-mac-address: true
These settings configure the
enp1s0
device to accept all traffic.Apply the network settings:
# nmstatectl apply ~/enp1s0.yml
Verification
Verify that the
802-3-ethernet.accept-all-mac-addresses
mode is enabled:# nmstatectl show enp1s0 interfaces: - name: enp1s0 type: ethernet state: up accept-all-mac-addresses: true ...
The
802-3-ethernet.accept-all-mac-addresses: true
indicates that the mode is enabled.
Additional resources
-
nmstatectl(8)
man page -
/usr/share/doc/nmstate/examples/
directory
Chapter 47. Mirroring a network interface by using nmcli
Network administrators can use port mirroring to replicate inbound and outbound network traffic being communicated from one network device to another. Mirroring traffic of an interface can be helpful in the following situations:
- To debug networking issues and tune the network flow
- To inspect and analyze the network traffic
- To detect an intrusion
Prerequisites
- A network interface to mirror the network traffic to.
Procedure
Add a network connection profile that you want to mirror the network traffic from:
# nmcli connection add type ethernet ifname enp1s0 con-name enp1s0 autoconnect no
Attach a
prio
qdisc
toenp1s0
for the egress (outgoing) traffic with the10:
handle:# nmcli connection modify enp1s0 +tc.qdisc "root prio handle 10:"
The
prio
qdisc
attached without children allows attaching filters.Add a
qdisc
for the ingress traffic, with theffff:
handle:# nmcli connection modify enp1s0 +tc.qdisc "ingress handle ffff:"
Add the following filters to match packets on the ingress and egress
qdiscs
, and to mirror them toenp7s0
:# nmcli connection modify enp1s0 +tc.tfilter "parent ffff: matchall action mirred egress mirror dev enp7s0" # nmcli connection modify enp1s0 +tc.tfilter "parent 10: matchall action mirred egress mirror dev enp7s0"
The
matchall
filter matches all packets, and themirred
action redirects packets to destination.Activate the connection:
# nmcli connection up enp1s0
Verification
Install the
tcpdump
utility:# yum install tcpdump
Display the traffic mirrored on the target device (
enp7s0
):# tcpdump -i enp7s0
Additional resources
Chapter 48. Using nmstate-autoconf to automatically configure the network state using LLDP
Network devices can use the Link Layer Discovery Protocol (LLDP) to advertise their identity, capabilities, and neighbors in a LAN. The nmstate-autoconf
utility can use this information to automatically configure local network interfaces.
The nmstate-autoconf
utility is provided as a Technology Preview only. Technology Preview features are not supported with Red Hat production Service Level Agreements (SLAs), might not be functionally complete, and Red Hat does not recommend using them for production. These previews provide early access to upcoming product features, enabling customers to test functionality and provide feedback during the development process.
See Technology Preview Features Support Scope on the Red Hat Customer Portal for information about the support scope for Technology Preview features.
48.1. Using nmstate-autoconf to automatically configure network interfaces
The nmstate-autoconf
utility uses LLDP to identify the VLAN settings of interfaces connected to a switch to configure local devices.
This procedure assumes the following scenario and that the switch broadcasts the VLAN settings using LLDP:
-
The
enp1s0
andenp2s0
interfaces of the RHEL server are connected to switch ports that are configured with VLAN ID100
and VLAN nameprod-net
. -
The
enp3s0
interface of the RHEL server is connected to a switch port that is configured with VLAN ID200
and VLAN namemgmt-net
.
The nmstate-autoconf
utility then uses this information to create the following interfaces on the server:
-
bond100
- A bond interface withenp1s0
andenp2s0
as ports. -
prod-net
- A VLAN interface on top ofbond100
with VLAN ID100
. -
mgmt-net
- A VLAN interface on top ofenp3s0
with VLAN ID200
If you connect multiple network interfaces to different switch ports for which LLDP broadcasts the same VLAN ID, nmstate-autoconf
creates a bond with these interfaces and, additionally, configures the common VLAN ID on top of it.
Prerequisites
-
The
nmstate
package is installed. - LLDP is enabled on the network switch.
- The Ethernet interfaces are up.
Procedure
Enable LLDP on the Ethernet interfaces:
Create a YAML file, for example
~/enable-lldp.yml
, with the following content:interfaces: - name: enp1s0 type: ethernet lldp: enabled: true - name: enp2s0 type: ethernet lldp: enabled: true - name: enp3s0 type: ethernet lldp: enabled: true
Apply the settings to the system:
# nmstatectl apply ~/enable-lldp.yml
Configure the network interfaces using LLDP:
Optional, start a dry-run to display and verify the YAML configuration that
nmstate-autoconf
generates:# nmstate-autoconf -d enp1s0,enp2s0,enp3s0 --- interfaces: - name: prod-net type: vlan state: up vlan: base-iface: bond100 id: 100 - name: mgmt-net type: vlan state: up vlan: base-iface: enp3s0 id: 200 - name: bond100 type: bond state: up link-aggregation: mode: balance-rr port: - enp1s0 - enp2s0
Use
nmstate-autoconf
to generate the configuration based on information received from LLDP, and apply the settings to the system:# nmstate-autoconf enp1s0,enp2s0,enp3s0
Next steps
If there is no DHCP server in your network that provides the IP settings to the interfaces, configure them manual. For details, see:
Verification
Display the settings of the individual interfaces:
# nmstatectl show <interface_name>
Additional resources
-
nmstate-autoconf(8)
man page
Chapter 49. Configuring 802.3 link settings
Auto-negotiation is a feature of the IEEE 802.3u Fast Ethernet protocol. It targets the device ports to provide an optimal performance of speed, duplex mode, and flow control for information exchange over a link. Using the auto-negotiation protocol, you have optimal performance of data transfer over the Ethernet.
To utilize maximum performance of auto-negotiation, use the same configuration on both sides of a link.
49.1. Configuring 802.3 link settings using the nmcli
utility
To configure the 802.3 link settings of an Ethernet connection, modify the following configuration parameters:
-
802-3-ethernet.auto-negotiate
-
802-3-ethernet.speed
-
802-3-ethernet.duplex
Procedure
Display the current settings of the connection:
# nmcli connection show Example-connection ... 802-3-ethernet.speed: 0 802-3-ethernet.duplex: -- 802-3-ethernet.auto-negotiate: no ...
You can use these values if you need to reset the parameters in case of any problems.
Set the speed and duplex link settings:
# nmcli connection modify Example-connection 802-3-ethernet.auto-negotiate yes 802-3-ethernet.speed 10000 802-3-ethernet.duplex full
This command enables auto-negotiation and sets the speed of the connection to
10000
Mbit full duplex.Reactivate the connection:
# nmcli connection up Example-connection
Verification
Use the
ethtool
utility to verify the values of Ethernet interfaceenp1s0
:# ethtool enp1s0 Settings for enp1s0: ... Speed: 10000 Mb/s Duplex: Full Auto-negotiation: on ... Link detected: yes
Additional resources
-
nm-settings(5)
man page
Chapter 50. Getting started with DPDK
The data plane development kit (DPDK) provides libraries and network drivers to accelerate packet processing in user space.
Administrators use DPDK, for example, in virtual machines to use Single Root I/O Virtualization (SR-IOV) to reduce latencies and increase I/O throughput.
Red Hat does not support experimental DPDK APIs.
50.1. Installing the dpdk package
To use DPDK, install the dpdk
package.
Procedure
Use the
yum
utility to install thedpdk
package:# yum install dpdk
50.2. Additional resources
Chapter 51. Getting started with TIPC
Transparent Inter-process Communication (TIPC), which is also known as Cluster Domain Sockets
, is an Inter-process Communication (IPC) service for cluster-wide operation.
Applications that are running in a high-available and dynamic cluster environment have special needs. The number of nodes in a cluster can vary, routers can fail, and, due to load balancing considerations, functionality can be moved to different nodes in the cluster. TIPC minimizes the effort by application developers to deal with such situations, and maximizes the chance that they are handled in a correct and optimal way. Additionally, TIPC provides a more efficient and fault-tolerant communication than general protocols, such as TCP.
51.1. The architecture of TIPC
TIPC is a layer between applications using TIPC and a packet transport service (bearer
), and spans the level of transport, network, and signaling link layers. However, TIPC can use a different transport protocol as bearer, so that, for example, a TCP connection can serve as a bearer for a TIPC signaling link.
TIPC supports the following bearers:
- Ethernet
- InfiniBand
- UDP protocol
TIPC provides a reliable transfer of messages between TIPC ports, that are the endpoints of all TIPC communication.
The following is a diagram of the TIPC architecture:
![TIPC architectural overview](https://access.redhat.com/webassets/avalon/d/Red_Hat_Enterprise_Linux-8-Configuring_and_managing_networking-en-US/images/05f0a1f83cfa23805891dbf10b7b6078/TIPC-architectural-overview.png)
51.2. Loading the tipc module when the system boots
Before you can use the TIPC protocol, you must load the tipc
kernel module. You can configure Red Hat Enterprise Linux to automatically load this kernel module automatically when the system boots.
Procedure
Create the
/etc/modules-load.d/tipc.conf
file with the following content:tipc
Restart the
systemd-modules-load
service to load the module without rebooting the system:# systemctl start systemd-modules-load
Verification
Use the following command to verify that RHEL loaded the
tipc
module:# lsmod | grep tipc tipc 311296 0
If the command shows no entry for the
tipc
module, RHEL failed to load it.
Additional resources
-
modules-load.d(5)
man page
51.3. Creating a TIPC network
To create a TIPC network, perform this procedure on each host that should join the TIPC network.
The commands configure the TIPC network only temporarily. To permanently configure TIPC on a node, use the commands of this procedure in a script, and configure RHEL to execute that script when the system boots.
Prerequisites
-
The
tipc
module has been loaded. For details, see Loading the tipc module when the system boots
Procedure
Optional: Set a unique node identity, such as a UUID or the node’s host name:
# tipc node set identity host_name
The identity can be any unique string consisting of a maximum 16 letters and numbers.
You cannot set or change an identity after this step.
Add a bearer. For example, to use Ethernet as media and
enp0s1
device as physical bearer device, enter:# tipc bearer enable media eth device enp1s0
- Optional: For redundancy and better performance, attach further bearers using the command from the previous step. You can configure up to three bearers, but not more than two on the same media.
- Repeat all previous steps on each node that should join the TIPC network.
Verification
Display the link status for cluster members:
# tipc link list broadcast-link: up 5254006b74be:enp1s0-525400df55d1:enp1s0: up
This output indicates that the link between bearer
enp1s0
on node5254006b74be
and bearerenp1s0
on node525400df55d1
isup
.Display the TIPC publishing table:
# tipc nametable show Type Lower Upper Scope Port Node 0 1795222054 1795222054 cluster 0 5254006b74be 0 3741353223 3741353223 cluster 0 525400df55d1 1 1 1 node 2399405586 5254006b74be 2 3741353223 3741353223 node 0 5254006b74be
-
The two entries with service type
0
indicate that two nodes are members of this cluster. -
The entry with service type
1
represents the built-in topology service tracking service. -
The entry with service type
2
displays the link as seen from the issuing node. The range limit3741353223
represents the peer endpoint’s address (a unique 32-bit hash value based on the node identity) in decimal format.
-
The two entries with service type
Additional resources
-
tipc-bearer(8)
man page -
tipc-namespace(8)
man page
51.4. Additional resources
Red Hat recommends to use other bearer level protocols to encrypt the communication between nodes based on the transport media. For example:
- MACSec: See Using MACsec to encrypt layer 2 traffic
- IPsec: See Configuring a VPN with IPsec
-
For examples of how to use TIPC, clone the upstream GIT repository using the
git clone git://git.code.sf.net/p/tipc/tipcutils
command. This repository contains the source code of demos and test programs that use TIPC features. Note that this repository is not provided by Red Hat. -
/usr/share/doc/kernel-doc-<kernel_version>/Documentation/output/networking/tipc.html
provided by thekernel-doc
package.
Chapter 52. Automatically configuring network interfaces in public clouds using nm-cloud-setup
Usually, a virtual machine (VM) has only one interface that is configurable by DHCP. However, DHCP cannot configure VMs with multiple network entities, such as interfaces, IP subnets, and IP addresses. Additionally, you cannot apply settings when the VM instance is running. To solve this runtime configuration issue, the nm-cloud-setup
utility automatically retrieves configuration information from the metadata server of the cloud service provider and updates the network configuration of the host. The utility automatically picks up multiple network interfaces, multiple IP addresses, or IP subnets on one interface and helps to reconfigure the network of the running VM instance.
52.1. Configuring and pre-deploying nm-cloud-setup
To enable and configure network interfaces in public clouds, run nm-cloud-setup
as a timer and service.
On Red Hat Enterprise Linux On Demand and AWS golden images, nm-cloud-setup
is already enabled and no action is required.
Prerequisite
- A network connection exists.
The connection uses DHCP.
By default, NetworkManager creates a connection profile which uses DHCP. If no profile was created because you set the
no-auto-default
parameter in/etc/NetworkManager/NetworkManager.conf
, create this initial connection manually.
Procedure
Install the
nm-cloud-setup
package:# yum install NetworkManager-cloud-setup
Create and run the snap-in file for the
nm-cloud-setup
service:Use the following command to start editing the snap-in file:
# systemctl edit nm-cloud-setup.service
It is important to either start the service explicitly or reboot the system to make configuration settings effective.
Use the
systemd
snap-in file to configure the cloud provider innm-cloud-setup
. For example, to use Amazon EC2, enter:[Service] Environment=NM_CLOUD_SETUP_EC2=yes
You can set the following environment variables to enable the cloud provide you use:
-
NM_CLOUD_SETUP_AZURE
for Microsoft Azure -
NM_CLOUD_SETUP_EC2
for Amazon EC2 (AWS) -
NM_CLOUD_SETUP_GCP
for Google Cloud Platform(GCP) -
NM_CLOUD_SETUP_ALIYUN
for Alibaba Cloud (Aliyun)
-
- Save the file and quit the editor.
Reload the
systemd
configuration:# systemctl daemon-reload
Enable and start the
nm-cloud-setup
service:# systemctl enable --now nm-cloud-setup.service
Enable and start the
nm-cloud-setup
timer:# systemctl enable --now nm-cloud-setup.timer
Additional resources
-
nm-cloud-setup(8)
man page - Configuring an Ethernet connection
52.2. Understanding the role of IMDSv2 and nm-cloud-setup in the RHEL EC2 instance
The instance metadata service (IMDS) in Amazon EC2 allows you to manage permissions to access instance metadata of a running Red Hat Enterprise Linux (RHEL) EC2 instance. The RHEL EC2 instance uses IMDS version 2 (IMDSv2), a session-oriented method. By using the nm-cloud-setup
utility, administrators can reconfigure the network and automatically update the configuration of running RHEL EC2 instances. The nm-cloud-setup
utility handles IMDSv2 API calls by using IMDSv2 tokens without any user intervention.
-
IMDS runs on a link-local address
169.254.169.254
for providing access to native applications on a RHEL EC2 instance. - After you have specified and configured IMDSv2 for each RHEL EC2 instance for applications and users, you can no longer access IMDSv1.
- By using IMDSv2, the RHEL EC2 instance maintains metadata without using the IAM role while remaining accessible through the IAM role.
-
When the RHEL EC2 instance boots, the
nm-cloud-setup
utility automatically runs to fetch the EC2 instance API access token for using the RHEL EC2 instance API.
Use the IMDSv2 token as an HTTP header to check the details of the EC2 environment.
Additional resources
-
nm-cloud-setup(8)
man page