Configuring and managing networking


Red Hat Enterprise Linux 8

Managing network interfaces, firewalls, and advanced networking features

Red Hat Customer Content Services

Abstract

Using the networking capabilities of Red Hat Enterprise Linux (RHEL), you can configure your host to meet your organization's network and security requirements. For example:
  • 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, the nftables 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.
Warning

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:

  1. 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 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 ifcfg file.

    If the system uses only NetworkManager connection profiles in keyfile format, udev skips this step.

  2. 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 the biosdevname utility renames the interface according to its naming policy, if it was not renamed in the previous step.

    Note

    Install and use biosdevname only on Dell systems.

  3. /usr/lib/udev/rules.d/75-net-description.rules

    This file defines how udev examines the network interface and sets the properties in udev-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.

  4. /usr/lib/udev/rules.d/80-net-setup-link.rules

    This file calls the net_setup_link builtin of the udev service, and udev renames the interface based on the order of the policies in the NamePolicy 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.

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:

PolicyDescriptionExample name

kernel

If the kernel indicates that a device name is predictable, udev does not rename this device.

lo

database

This policy assigns names based on mappings in the udev hardware database. For details, see the hwdb(7) man page on your system.

idrac

onboard

Device names incorporate firmware or BIOS-provided index numbers for onboard devices.

eno1

slot

Device names incorporate firmware or BIOS-provided PCI Express (PCIe) hot-plug slot-index numbers.

ens1

path

Device names incorporate the physical location of the connector of the hardware.

enp1s0

mac

Device names incorporate the MAC address. By default, Red Hat Enterprise Linux does not use this policy, but administrators can enable it.

enx525400d5e0fb

Additional resources

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 on your system. 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 on your system.

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

  1. 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.

  2. 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.

  3. 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
  4. Reboot the system.

    # reboot
  5. 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 address 00:00:5e:00:53:1a eno1np0, whereas it was named eno1 before.

  6. Identify which NetworkManager connection profile uses an interface with the previous name:

    # nmcli -f device,name connection show
    DEVICE  NAME
    eno1  example_profile
    ...
  7. Set the connection.interface-name property in the connection profile to the new interface name:

    # nmcli connection modify example_profile connection.interface-name "eno1np0"
  8. 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 example eno<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 example ens<FID_in_decimal>.

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

  1. 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
    ...
  2. 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.

  3. 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.

  4. 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.

  5. Convert the hexadecimal identifier to decimal, for example:

    # printf "%d\n" 0x00001402
    5122
  6. 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 example eno5122.
    • If UID uniqueness is not enforced, append the identifier to the ens prefix, for example ens5122.

Additional resources

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.

Important

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, and em.

Procedure

  1. Boot the Red Hat Enterprise Linux installation media.
  2. In the boot manager, follow these steps:

    1. Select the Install Red Hat Enterprise Linux <version> entry.
    2. Press Tab to edit the entry.
    3. Append net.ifnames.prefix=<prefix> to the kernel options.
    4. Press Enter to start the installation program.
  3. 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
    ...

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

  1. 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.

  2. Display the device type ID of the interface:

    # cat /sys/class/net/enp1s0/type
    1
  3. 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>"
    Important

    Use only 70-persistent-net.rules as a file name if you require consistent device names during the boot process. The dracut utility adds a file with this name to the initrd 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 to provider0:

    SUBSYSTEM=="net",ACTION=="add",ATTR{address}=="00:00:5e:00:53:1a",ATTR{type}=="1",NAME="provider0"
  4. 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.

  5. Identify which NetworkManager connection profile uses the interface that you want to rename:

    # nmcli -f device,name connection show
    DEVICE  NAME
    enp1s0  example_profile
    ...
  6. Unset the connection.interface-name property in the connection profile:

    # nmcli connection modify example_profile connection.interface-name ""
  7. 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"
  8. Reboot the system:

    # reboot
  9. 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
    ...
  10. 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.

  11. Reactivate the connection profile:

    # nmcli connection up example_profile

Additional resources

  • udev(7) man page on your system

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.
Note

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

  1. 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.

  2. 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.

  3. 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.

  4. 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
    ...
  5. 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 to auto (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
  6. 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 to auto (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
  7. 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.

  8. Activate the profile:

    # nmcli connection up Internal-LAN

Verification

  1. 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
  2. Display the IPv4 default gateway:

    # ip route show default
    default via 192.0.2.254 dev enp1s0 proto static metric 102
  3. Display the IPv6 default gateway:

    # ip -6 route show default
    default via 2001:db8:1::ffee dev enp1s0 proto static metric 102 pref medium
  4. 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.

  5. 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 on your system

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

  1. 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.

  2. 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>"
  3. 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 set Example Connection as ID, enter set connection.id Example Connection.

  4. Display the current settings of the connection profile:

    nmcli> print
    ...
    connection.interface-name:     enp1s0
    connection.autoconnect:        yes
    ipv4.method:                   auto
    ipv6.method:                   auto
    ...
  5. If you create a new connection profile, set the network interface:

    nmcli> set connection.interface-name enp1s0
  6. Configure the IPv4 settings:

    • To use DHCP, enter:

      nmcli> set ipv4.method auto

      Skip this step if ipv4.method is already set to auto (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
  7. 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 to auto (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
  8. Save and activate the connection:

    nmcli> save persistent
  9. Leave the interactive mode:

    nmcli> quit

Verification

  1. 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
  2. Display the IPv4 default gateway:

    # ip route show default
    default via 192.0.2.254 dev enp1s0 proto static metric 102
  3. Display the IPv6 default gateway:

    # ip -6 route show default
    default via 2001:db8:1::ffee dev enp1s0 proto static metric 102 pref medium
  4. 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.

  5. 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) and nmcli(1) man pages on your system

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.

Note

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

  1. 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             --
    ...
  2. Start nmtui:

    # nmtui
  3. Select Edit a connection, and press Enter.
  4. Choose whether to add a new connection profile or to modify an existing one:

    • To create a new profile:

      1. Press Add.
      2. 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.
  5. 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.

  6. If you create a new connection profile, enter the network device name into the Device field.
  7. 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 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:

      1. Press Show next to the protocol you want to configure to display additional fields.
      2. 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.

      3. Enter the address of the default gateway.
      4. Press Add next to DNS servers, and enter the DNS server address.
      5. 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

    nmtui ethernet static IP
  8. Press OK to create and automatically activate the new connection.
  9. Press Back to return to the main menu.
  10. Select Quit, and press Enter to close the nmtui application.

Verification

  1. 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
  2. Display the IPv4 default gateway:

    # ip route show default
    default via 192.0.2.254 dev enp1s0 proto static metric 102
  3. Display the IPv6 default gateway:

    # ip -6 route show default
    default via 2001:db8:1::ffee dev enp1s0 proto static metric 102 pref medium
  4. 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.

  5. 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

  1. Press the Super key, enter Settings, and press Enter.
  2. Select Network in the navigation on the left.
  3. Choose whether to add a new connection profile or to modify an existing one:

    • To create a new profile, click the + button next to the Ethernet entry.
    • To modify an existing profile, click the gear icon next to the profile entry.
  4. 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.

  5. 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:

      IP settings gnome settings
  6. Depending on whether you add or modify a connection profile, click the Add or Apply button to save the connection.

    The GNOME control-center automatically activates the connection.

Verification

  1. 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
  2. Display the IPv4 default gateway:

    # ip route show default
    default via 192.0.2.254 dev enp1s0 proto static metric 102
  3. Display the IPv6 default gateway:

    # ip -6 route show default
    default via 2001:db8:1::ffee dev enp1s0 proto static metric 102 pref medium
  4. 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.

  5. 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

  1. Open a terminal, and enter:

    $ nm-connection-editor
  2. Choose whether to add a new connection profile or to modify an existing one:

    • To create a new profile:

      1. Click the + button
      2. Select Ethernet as connection type, and click Create.
    • To modify an existing profile, double-click the profile entry.
  3. 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.

  4. If you create a new profile, select the device on the Ethernet tab:

    ethernet connection settings

  5. 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:

      IP settings nm connection editor
  6. Click Save.
  7. Close nm-connection-editor.

Verification

  1. 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
  2. Display the IPv4 default gateway:

    # ip route show default
    default via 192.0.2.254 dev enp1s0 proto static metric 102
  3. Display the IPv6 default gateway:

    # ip -6 route show default
    default via 2001:db8:1::ffee dev enp1s0 proto static metric 102 pref medium
  4. 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.

  5. 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

  1. 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
  2. Apply the settings to the system:

    # nmstatectl apply ~/create-ethernet-profile.yml

Verification

  1. Display the current state in YAML format:

    # nmstatectl show enp1s0
  2. 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
  3. Display the IPv4 default gateway:

    # ip route show default
    default via 192.0.2.254 dev enp1s0 proto static metric 102
  4. Display the IPv6 default gateway:

    # ip -6 route show default
    default via 2001:db8:1::ffee dev enp1s0 proto static metric 102 pref medium
  5. 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.

  6. 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 on your system
  • /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.

Typically, administrators want to reuse a playbook and not maintain individual playbooks for each host to which Ansible should assign static IP addresses. In this case, you can use variables in the playbook and maintain the settings in the inventory. As a result, you need only one playbook to dynamically assign individual settings to multiple hosts.

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 configuration.
  • The managed nodes use NetworkManager to configure the network.

Procedure

  1. Edit the ~/inventory file, and append the host-specific settings to the host entries:

    managed-node-01.example.com interface=enp1s0 ip_v4=192.0.2.1/24 ip_v6=2001:db8:1::1/64 gateway_v4=192.0.2.254 gateway_v6=2001:db8:1::fffe
    
    managed-node-02.example.com interface=enp1s0 ip_v4=192.0.2.2/24 ip_v6=2001:db8:1::2/64 gateway_v4=192.0.2.254 gateway_v6=2001:db8:1::fffe
  2. Create a playbook file, for example ~/playbook.yml, with the following content:

    ---
    - name: Configure the network
      hosts: managed-node-01.example.com,managed-node-02.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: "{{ interface }}"
                interface_name: "{{ interface }}"
                type: ethernet
                autoconnect: yes
                ip:
                  address:
                    - "{{ ip_v4 }}"
                    - "{{ ip_v6 }}"
                  gateway4: "{{ gateway_v4 }}"
                  gateway6: "{{ gateway_v6 }}"
                  dns:
                    - 192.0.2.200
                    - 2001:db8:1::ffbb
                  dns_search:
                    - example.com
                state: up

    This playbook reads certain values dynamically for each host from the inventory file and uses static values in the playbook for settings which are the same for all hosts.

    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.

  3. 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.

  4. 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 servers 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

  1. 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 not 0000:00:02.0.

    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.

  2. 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.

  3. 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

  1. 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).

  2. Apply the settings to the system:

    # nmstatectl apply ~/create-ethernet-profile.yml

Verification

  1. Display the current state in YAML format:

    # nmstatectl show enp1s0
  2. 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
  3. Display the IPv4 default gateway:

    # ip route show default
    default via 192.0.2.254 dev enp1s0 proto static metric 102
  4. Display the IPv6 default gateway:

    # ip -6 route show default
    default via 2001:db8:1::ffee dev enp1s0 proto static metric 102 pref medium
  5. 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.

  6. 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 on your system
  • /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 servers configuration.
  • A DHCP server and SLAAC are available in the network.
  • The managed nodes use the NetworkManager service to configure the network.

Procedure

  1. 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.

  2. 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.

  3. 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 servers 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

  1. 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 not 0000:00:02.0.
    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.

  2. 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.

  3. 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

  1. 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

  1. 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 the match.interface-name parameter and, therefore, the connection profiles have the same Universally Unique Identifier (UUID).

  2. 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 on your system
  • 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

  1. 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
  2. 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

  1. 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
    ...
  2. 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 on your system
  • 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 modeConfiguration on the switch

0 - balance-rr

Requires static EtherChannel enabled, not Link Aggregation Control Protocol (LACP)-negotiated.

1 - active-backup

No configuration required on the switch.

2 - balance-xor

Requires static EtherChannel enabled, not LACP-negotiated.

3 - broadcast

Requires static EtherChannel enabled, not LACP-negotiated.

4 - 802.3ad

Requires LACP-negotiated EtherChannel enabled.

5 - balance-tlb

No configuration required on the switch.

6 - balance-alb

No configuration required on the switch.

For details how to configure your switch, see the documentation of the switch.

Important

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

Procedure

  1. 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 the active-backup mode.

    To additionally set a Media Independent Interface (MII) monitoring interval, add the miimon=interval option to the bond.options property, for example:

    # nmcli connection add type bond con-name bond0 ifname bond0 bond.options "mode=active-backup,miimon=1000"
  2. 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 and enp8s0 are not configured. To use these devices as ports, add connection profiles in the next step.
    • bridge0 and bridge1 have existing connection profiles. To use these devices as ports, modify their profiles in the next step.
  3. Assign interfaces to the bond:

    1. 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 and enp8s0, and add them to the bond0 connection.

    2. To assign an existing connection profile to the bond:

      1. Set the master parameter of these connections to bond0:

        # nmcli connection modify bridge0 master bond0
        # nmcli connection modify bridge1 master bond0

        These commands assign the existing connection profiles named bridge0 and bridge1 to the bond0 connection.

      2. Reactivate the connections:

        # nmcli connection up bridge0
        # nmcli connection up bridge1
  4. 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
  5. 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
  6. 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>
  7. Activate the connection:

    # nmcli connection up bond0
  8. 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:

    1. Enable the connection.autoconnect-slaves parameter of the bond’s connection:

      # nmcli connection modify bond0 connection.autoconnect-slaves 1
    2. Reactivate the bridge:

      # nmcli connection up bond0

Verification

  1. 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.

  2. 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

Procedure

  1. Log in to the RHEL 8 web console.

    For details, see Logging in to the web console.

  2. Select the Networking tab in the navigation on the left side of the screen.
  3. Click Add bond in the Interfaces section.
  4. Enter the name of the bond device you want to create.
  5. Select the interfaces that should be members of the bond.
  6. 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.

  7. Set the link monitoring mode. For example, when you use the Adaptive load balancing mode, set it to ARP.
  8. Optional: Adjust the monitoring interval, link up delay, and link down delay settings. Typically, you only change the defaults for troubleshooting purposes.

    bond settings
  9. Click Apply.
  10. By default, the bond uses a dynamic IP address. If you want to set a static IP address:

    1. Click the name of the bond in the Interfaces section.
    2. Click Edit next to the protocol you want to configure.
    3. Select Manual next to Addresses, and enter the IP address, prefix, and default gateway.
    4. In the DNS section, click the + button, and enter the IP address of the DNS server. Repeat this step to set multiple DNS servers.
    5. In the DNS search domains section, click the + button, and enter the search domain.
    6. If the interface requires static routes, configure them in the Routes section.

      bond team bridge vlan.ipv4
    7. Click Apply

Verification

  1. 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:

    bond verify
  2. 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.

  3. 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.

Note

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

  1. 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             --
    ...
  2. Start nmtui:

    # nmtui
  3. Select Edit a connection, and press Enter.
  4. Press Add.
  5. Select Bond from the list of network types, and press Enter.
  6. 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.

  7. Enter the bond device name to be created into the Device field.
  8. Add ports to the bond to be created:

    1. Press Add next to the Slaves list.
    2. Select the type of the interface you want to add as port to the bond, for example, Ethernet.
    3. Optional: Enter a name for the NetworkManager profile to be created for this bond port.
    4. Enter the port’s device name into the Device field.
    5. Press OK to return to the window with the bond settings.

      Figure 3.1. Adding an Ethernet device as port to a bond

      nmtui bond add port
    6. Repeat these steps to add more ports to the bond.
  9. Set the bond mode. Depending on the value you set, nmtui displays additional fields for settings that are related to the selected mode.
  10. 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:

      1. Press Show next to the protocol you want to configure to display additional fields.
      2. 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.

      3. Enter the address of the default gateway.
      4. Press Add next to DNS servers, and enter the DNS server address.
      5. 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

    nmtui bond static IP
  11. Press OK to create and automatically activate the new connection.
  12. Press Back to return to the main menu.
  13. Select Quit, and press Enter to close the nmtui application.

Verification

  1. 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.

  2. 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

  1. Open a terminal, and enter nm-connection-editor:

    $ nm-connection-editor
  2. Click the + button to add a new connection.
  3. Select the Bond connection type, and click Create.
  4. On the Bond tab:

    1. Optional: Set the name of the bond interface in the Interface name field.
    2. Click the Add button to add a network interface as a port to the bond.

      1. Select the connection type of the interface. For example, select Ethernet for a wired connection.
      2. Optional: Set a connection name for the port.
      3. 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.
      4. Click Save.
    3. Repeat the previous step for each interface you want to add to the bond:

      add nic to bond in nm connection editor

    4. Optional: Set other options, such as the Media Independent Interface (MII) monitoring interval.
  5. 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:

      bond IP settings nm connection editor

  6. Click Save.
  7. Close nm-connection-editor.

Verification

  1. 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.

  2. 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

  1. 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 and enp7s0
    • 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
  2. Apply the settings to the system:

    # nmstatectl apply ~/create-bond.yml

Verification

  1. Display the status of the devices and connections:

    # nmcli device status
    DEVICE      TYPE      STATE      CONNECTION
    bond0       bond      connected  bond0
  2. 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
    ...
  3. Display the connection settings in YAML format:

    # nmstatectl show bond0

Additional resources

  • nmstatectl(8) man page on your system
  • /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

  1. 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.

  2. 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.

  3. 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 the enp11s0u1 Ethernet device
    • Wi-Fi associated with the wlp1s0 Wi-Fi device

Procedure

  1. 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.

  2. 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
  3. 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
  4. 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.

  5. Assign the connection profile of the Ethernet connection to the bond:

    # nmcli connection modify Docking_station master bond0
  6. Assign the connection profile of the Wi-Fi connection to the bond:

    # nmcli connection modify Wi-Fi master bond0
  7. 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.

  8. 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.

  9. Configure that NetworkManager automatically activates ports when the bond0 device is activated:

    # nmcli connection modify bond0 connection.autoconnect-slaves 1
  10. 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

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 Linux bonding driver supports the following modes:

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 the Balance-xor is compliance. The 802.3ad 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 balancing

    With the bonding option tlb_dynamic_lb=0, this bonding mode uses the xmit_hash_policy bonding option to balance transmit. The primary option defines the preferred port of the bonding interface.

See description xmit_hash_policy bonding parameter.

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 option tlb_dynamic_lb=0, this bonding mode uses the xmit_hash_policy bonding option to balance transmit. See description xmit_hash_policy bonding parameter.

Additional resources

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 skb_flow_dissect() function to obtain the header fields

XOR of source and destination ports and IP addresses inside a supported tunnel, for example, VXLAN. This mode relies on skb_flow_dissect() function to obtain the header fields

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 layer2 transmit policy

For non-IP traffic, the formula is the same as for the layer2 transmit policy

   

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.
Important

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.

4.3. Configuring a NIC team by using nmcli

To configure a network interface controller (NIC) team on the command line, use the nmcli utility.

Important

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

Procedure

  1. 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 the activebackup runner.

  2. Optional: Set a link watcher. For example, to set the ethtool link watcher in the team0 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 the ethtool link watcher and set its delay-up parameter to 2500 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 the delay-up parameter and the arp_ping link watcher with the source-host and target-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"
  3. 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 and enp8s0 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 and bond1 have existing connection profiles. To use these devices as ports, modify their profiles in the next step.
  4. Assign the port interfaces to the team:

    1. 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 and enp8s0, and add them to the team0 connection.

    2. To assign an existing connection profile to the team:

      1. Set the master parameter of these connections to team0:

        # nmcli connection modify bond0 master team0
        # nmcli connection modify bond1 master team0

        These commands assign the existing connection profiles named bond0 and bond1 to the team0 connection.

      2. Reactivate the connections:

        # nmcli connection up bond0
        # nmcli connection up bond1
  5. 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
  6. 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
  7. 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.

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.

Important

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

Procedure

  1. Log in to the RHEL 8 web console.

    For details, see Logging in to the web console.

  2. Select the Networking tab in the navigation on the left side of the screen.
  3. Click Add team in the Interfaces section.
  4. Enter the name of the team device you want to create.
  5. Select the interfaces that should be ports of the team.
  6. Select the runner of the team.

    If you select Load balancing or 802.3ad LACP, the web console shows the additional field Balancer.

  7. Set the link watcher:

    • If you select Ethtool, additionally, set a link up and link down delay.
    • If you set ARP ping or NSNA ping, additionally, set a ping interval and ping target.
    team settings
  8. Click Apply.
  9. By default, the team uses a dynamic IP address. If you want to set a static IP address:

    1. Click the name of the team in the Interfaces section.
    2. Click Edit next to the protocol you want to configure.
    3. Select Manual next to Addresses, and enter the IP address, prefix, and default gateway.
    4. In the DNS section, click the + button, and enter the IP address of the DNS server. Repeat this step to set multiple DNS servers.
    5. In the DNS search domains section, click the + button, and enter the search domain.
    6. If the interface requires static routes, configure them in the Routes section.

      bond team bridge vlan.ipv4
    7. Click Apply

Verification

  1. 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.

    team verify
  2. 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.

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.

Important

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 and NetworkManager-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

  1. Open a terminal, and enter nm-connection-editor:

    $ nm-connection-editor
  2. Click the + button to add a new connection.
  3. Select the Team connection type, and click Create.
  4. On the Team tab:

    1. Optional: Set the name of the team interface in the Interface name field.
    2. Click the Add button to add a new connection profile for a network interface and adding the profile as a port to the team.

      1. Select the connection type of the interface. For example, select Ethernet for a wired connection.
      2. Optional: Set a connection name for the port.
      3. 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.
      4. Click Save.
    3. Repeat the previous step for each interface you want to add to the team.

      add nic to team in nm connection editor

    4. Click the Advanced button to set advanced options to the team connection.

      1. On the Runner tab, select the runner.
      2. On the Link Watcher tab, set the link watcher and its optional settings.
      3. Click OK.
  5. 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:

      team IP settings nm connection editor

  6. Click Save.
  7. 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

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 and ipv6.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

  1. Display the network interfaces:

    # nmcli device status
    DEVICE   TYPE      STATE         CONNECTION
    enp1s0   ethernet  disconnected  enp1s0
    bridge0  bridge    connected     bridge0
    bond0    bond      connected     bond0
    ...
  2. Create the VLAN interface. For example, to create a VLAN interface named vlan10 that uses enp1s0 as its parent interface and that tags packets with VLAN ID 10, 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 to 4094.

  3. 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
  4. 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
  5. 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
  6. 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 on your system

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.

Procedure

  1. Log in to the RHEL 8 web console.

    For details, see Logging in to the web console.

  2. Select the Networking tab in the navigation on the left side of the screen.
  3. Click Add VLAN in the Interfaces section.
  4. Select the parent device.
  5. Enter the VLAN ID.
  6. Enter the name of the VLAN device or keep the automatically-generated name.

    vlan settings
  7. Click Apply.
  8. By default, the VLAN device uses a dynamic IP address. If you want to set a static IP address:

    1. Click the name of the VLAN device in the Interfaces section.
    2. Click Edit next to the protocol you want to configure.
    3. Select Manual next to Addresses, and enter the IP address, prefix, and default gateway.
    4. In the DNS section, click the + button, and enter the IP address of the DNS server. Repeat this step to set multiple DNS servers.
    5. In the DNS search domains section, click the + button, and enter the search domain.
    6. If the interface requires static routes, configure them in the Routes section.

      bond team bridge vlan.ipv4
    7. Click Apply

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:

    vlan verify

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.

Note

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 and ipv6.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

  1. 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             --
    ...
  2. Start nmtui:

    # nmtui
  3. Select Edit a connection, and press Enter.
  4. Press Add.
  5. Select VLAN from the list of network types, and press Enter.
  6. 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.

  7. Enter the VLAN device name to be created into the Device field.
  8. Enter the name of the device on which you want to configure VLAN tagging into the Parent field.
  9. Enter the VLAN ID. The ID must be within the range from 0 to 4094.
  10. 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:

      1. Press Show next to the protocol you want to configure to display additional fields.
      2. 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.

      3. Enter the address of the default gateway.
      4. Press Add next to DNS servers, and enter the DNS server address.
      5. 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

    nmtui vlan static IP
  11. Press OK to create and automatically activate the new connection.
  12. Press Back to return to the main menu.
  13. 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

  1. Open a terminal, and enter nm-connection-editor:

    $ nm-connection-editor
  2. Click the + button to add a new connection.
  3. Select the VLAN connection type, and click Create.
  4. On the VLAN tab:

    1. Select the parent interface.
    2. Select the VLAN id. Note that the VLAN must be within the range from 0 to 4094.
    3. By default, the VLAN connection inherits the maximum transmission unit (MTU) from the parent interface. Optionally, set a different MTU value.
    4. Optional: Set the name of the VLAN interface and further VLAN-specific options.

      vlan settings nm connection editor

  5. 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:

      vlan IP settings nm connection editor

  6. Click Save.
  7. Close nm-connection-editor.

Verification

  1. 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

  1. 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
  2. Apply the settings to the system:

    # nmstatectl apply ~/create-vlan.yml

Verification

  1. Display the status of the devices and connections:

    # nmcli device status
    DEVICE      TYPE      STATE      CONNECTION
    vlan10      vlan      connected  vlan10
  2. 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
    ...
  3. Display the connection settings in YAML format:

    # nmstatectl show vlan0

Additional resources

  • nmstatectl(8) man page on your system
  • /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.

Note

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

Procedure

  1. 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 the managed 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.

  2. 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.

  3. 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

Procedure

  1. Create a bridge interface:

    # nmcli connection add type bridge con-name bridge0 ifname bridge0

    This command creates a bridge named bridge0, enter:

  2. 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 and enp8s0 are not configured. To use these devices as ports, add connection profiles in the next step.
    • bond0 and bond1 have existing connection profiles. To use these devices as ports, modify their profiles in the next step.
  3. Assign the interfaces to the bridge.

    1. 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 and enp8s0, and add them to the bridge0 connection.

    2. If you want to assign an existing connection profile to the bridge:

      1. Set the master parameter of these connections to bridge0:

        # nmcli connection modify bond0 master bridge0
        # nmcli connection modify bond1 master bridge0

        These commands assign the existing connection profiles named bond0 and bond1 to the bridge0 connection.

      2. Reactivate the connections:

        # nmcli connection up bond0
        # nmcli connection up bond1
  4. 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
  5. 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
  6. Optional: Configure further properties of the bridge. For example, to set the Spanning Tree Protocol (STP) priority of bridge0 to 16384, enter:

    # nmcli connection modify bridge0 bridge.priority '16384'

    By default, STP is enabled.

  7. Activate the connection:

    # nmcli connection up bridge0
  8. 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:

    1. Enable the connection.autoconnect-slaves parameter of the bridge connection:

      # nmcli connection modify bridge0 connection.autoconnect-slaves 1
    2. 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

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

Procedure

  1. Log in to the RHEL 8 web console.

    For details, see Logging in to the web console.

  2. Select the Networking tab in the navigation on the left side of the screen.
  3. Click Add bridge in the Interfaces section.
  4. Enter the name of the bridge device you want to create.
  5. Select the interfaces that should be ports of the bridge.
  6. Optional: Enable the Spanning tree protocol (STP) feature to avoid bridge loops and broadcast radiation.

    bridge settings
  7. Click Apply.
  8. By default, the bridge uses a dynamic IP address. If you want to set a static IP address:

    1. Click the name of the bridge in the Interfaces section.
    2. Click Edit next to the protocol you want to configure.
    3. Select Manual next to Addresses, and enter the IP address, prefix, and default gateway.
    4. In the DNS section, click the + button, and enter the IP address of the DNS server. Repeat this step to set multiple DNS servers.
    5. In the DNS search domains section, click the + button, and enter the search domain.
    6. If the interface requires static routes, configure them in the Routes section.

      bond team bridge vlan.ipv4
    7. Click Apply

Verification

  1. 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:

    bridge verify

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.

Note

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

  1. 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             --
    ...
  2. Start nmtui:

    # nmtui
  3. Select Edit a connection, and press Enter.
  4. Press Add.
  5. Select Bridge from the list of network types, and press Enter.
  6. 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.

  7. Enter the bridge device name to be created into the Device field.
  8. Add ports to the bridge to be created:

    1. Press Add next to the Slaves list.
    2. Select the type of the interface you want to add as port to the bridge, for example, Ethernet.
    3. Optional: Enter a name for the NetworkManager profile to be created for this bridge port.
    4. Enter the port’s device name into the Device field.
    5. Press OK to return to the window with the bridge settings.

      Figure 6.1. Adding an Ethernet device as port to a bridge

      nmtui bridge add port
    6. Repeat these steps to add more ports to the bridge.
  9. 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 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:

      1. Press Show next to the protocol you want to configure to display additional fields.
      2. 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.

      3. Enter the address of the default gateway.
      4. Press Add next to DNS servers, and enter the DNS server address.
      5. Press Add next to Search domains, and enter the DNS search domain.

    Figure 6.2. Example of a bridge connection without IP address settings

    nmtui bridge no IP
  10. Press OK to create and automatically activate the new connection.
  11. Press Back to return to the main menu.
  12. Select Quit, and press Enter to close the nmtui application.

Verification

  1. 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
  2. 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

  1. Open a terminal, and enter nm-connection-editor:

    $ nm-connection-editor
  2. Click the + button to add a new connection.
  3. Select the Bridge connection type, and click Create.
  4. On the Bridge tab:

    1. Optional: Set the name of the bridge interface in the Interface name field.
    2. Click the Add button to create a new connection profile for a network interface and adding the profile as a port to the bridge.

      1. Select the connection type of the interface. For example, select Ethernet for a wired connection.
      2. Optional: Set a connection name for the port device.
      3. 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.
      4. Click Save.
    3. Repeat the previous step for each interface you want to add to the bridge.

      add nic to bridge in nm connection editor

  5. Optional: Configure further bridge settings, such as Spanning Tree Protocol (STP) options.
  6. 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:

      bridge IP settings nm connection editor

  7. Click Save.
  8. 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.

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

  1. 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 and enp7s0
    • 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
  2. Apply the settings to the system:

    # nmstatectl apply ~/create-bridge.yml

Verification

  1. Display the status of the devices and connections:

    # nmcli device status
    DEVICE      TYPE      STATE      CONNECTION
    bridge0     bridge    connected  bridge0
  2. 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
    ...
  3. Display the connection settings in YAML format:

    # nmstatectl show bridge0

Additional resources

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.

Note

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

  1. 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.

  2. 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.

  3. Run the playbook:

    $ ansible-playbook ~/playbook.yml

Verification

  1. 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
  2. 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. Libreswan as an IPsec VPN implementation

In RHEL, you can configure a Virtual Private Network (VPN) by using the IPsec protocol, which is supported by the Libreswan application. Libreswan is a continuation of the Openswan application, and many examples from the Openswan documentation are interchangeable with Libreswan.

The IPsec protocol for a VPN is configured using the Internet Key Exchange (IKE) protocol. The terms IPsec and IKE are used interchangeably. An IPsec VPN is also called an IKE VPN, IKEv2 VPN, XAUTH VPN, Cisco VPN or IKE/IPsec VPN. A variant of an IPsec VPN that also uses the Layer 2 Tunneling Protocol (L2TP) is usually called an L2TP/IPsec VPN, which requires the xl2tpd package provided by the optional repository.

Libreswan is an open-source, user-space IKE implementation. IKE v1 and v2 are implemented as a user-level daemon. The IKE protocol is also encrypted. The IPsec protocol is implemented by the Linux kernel, and Libreswan configures the kernel to add and remove VPN tunnel configurations.

The IKE protocol uses UDP port 500 and 4500. The IPsec protocol consists of two protocols:

  • Encapsulated Security Payload (ESP), which has protocol number 50.
  • Authenticated Header (AH), which has protocol number 51.

The AH protocol is not recommended for use. Users of AH are recommended to migrate to ESP with null encryption.

The IPsec protocol provides two modes of operation:

  • Tunnel Mode (the default)
  • Transport Mode.

You can configure the kernel with IPsec without IKE. This is called manual keying. You can also configure manual keying using the ip xfrm commands, however, this is strongly discouraged for security reasons. Libreswan communicates with the Linux kernel using the Netlink interface. The kernel performs packet encryption and decryption.

Libreswan uses the Network Security Services (NSS) cryptographic library. NSS is certified for use with the Federal Information Processing Standard (FIPS) Publication 140-2.

Important

IKE/IPsec VPNs, implemented by Libreswan and the Linux kernel, is the only VPN technology recommended for use in RHEL. Do not use any other VPN technology without understanding the risks of doing so.

In RHEL, Libreswan follows system-wide cryptographic policies by default. This ensures that Libreswan uses secure settings for current threat models including IKEv2 as a default protocol. See Using system-wide crypto policies for more information.

Libreswan does not use the terms "source" and "destination" or "server" and "client" because IKE/IPsec are peer to peer protocols. Instead, it uses the terms "left" and "right" to refer to end points (the hosts). This also allows you to use the same configuration on both end points in most cases. However, administrators usually choose to always use "left" for the local host and "right" for the remote host.

The leftid and rightid options serve as identification of the respective hosts in the authentication process. See the ipsec.conf(5) man page for more information.

7.2. Authentication methods in Libreswan

Libreswan supports several authentication methods, each of which fits a different scenario.

Pre-Shared key (PSK)

Pre-Shared Key (PSK) is the simplest authentication method. For security reasons, do not use PSKs shorter than 64 random characters. In FIPS mode, PSKs must comply with a minimum-strength requirement depending on the integrity algorithm used. You can set PSK by using the authby=secret connection.

Raw RSA keys

Raw RSA keys are commonly used for static host-to-host or subnet-to-subnet IPsec configurations. Each host is manually configured with the public RSA keys of all other hosts, and Libreswan sets up an IPsec tunnel between each pair of hosts. This method does not scale well for large numbers of hosts.

You can generate a raw RSA key on a host using the ipsec newhostkey command. You can list generated keys by using the ipsec showhostkey command. The leftrsasigkey= line is required for connection configurations that use CKA ID keys. Use the authby=rsasig connection option for raw RSA keys.

X.509 certificates

X.509 certificates are commonly used for large-scale deployments with hosts that connect to a common IPsec gateway. A central certificate authority (CA) signs RSA certificates for hosts or users. This central CA is responsible for relaying trust, including the revocations of individual hosts or users.

For example, you can generate X.509 certificates using the openssl command and the NSS certutil command. Because Libreswan reads user certificates from the NSS database using the certificates' nickname in the leftcert= configuration option, provide a nickname when you create a certificate.

If you use a custom CA certificate, you must import it to the Network Security Services (NSS) database. You can import any certificate in the PKCS #12 format to the Libreswan NSS database by using the ipsec import command.

Warning

Libreswan requires an Internet Key Exchange (IKE) peer ID as a subject alternative name (SAN) for every peer certificate as described in section 3.1 of RFC 4945. Disabling this check by changing the require-id-on-certificated= option can make the system vulnerable to man-in-the-middle attacks.

Use the authby=rsasig connection option for authentication based on X.509 certificates using RSA with SHA-1 and SHA-2. You can further limit it for ECDSA digital signatures using SHA-2 by setting authby= to ecdsa and RSA Probabilistic Signature Scheme (RSASSA-PSS) digital signatures based authentication with SHA-2 through authby=rsa-sha2. The default value is authby=rsasig,ecdsa.

The certificates and the authby= signature methods should match. This increases interoperability and preserves authentication in one digital signature system.

NULL authentication

NULL authentication is used to gain mesh encryption without authentication. It protects against passive attacks but not against active attacks. However, because IKEv2 allows asymmetric authentication methods, NULL authentication can also be used for internet-scale opportunistic IPsec. In this model, clients authenticate the server, but servers do not authenticate the client. This model is similar to secure websites using TLS. Use authby=null for NULL authentication.

Protection against quantum computers

In addition to the previously mentioned authentication methods, you can use the Post-quantum Pre-shared Key (PPK) method to protect against possible attacks by quantum computers. Individual clients or groups of clients can use their own PPK by specifying a PPK ID that corresponds to an out-of-band configured pre-shared key.

Using IKEv1 with pre-shared keys protects against quantum attackers. The redesign of IKEv2 does not offer this protection natively. Libreswan offers the use of a Post-quantum Pre-shared Key (PPK) to protect IKEv2 connections against quantum attacks.

To enable optional PPK support, add ppk=yes to the connection definition. To require PPK, add ppk=insist. Then, each client can be given a PPK ID with a secret value that is communicated out-of-band (and preferably quantum-safe). The PPK’s should be very strong in randomness and not based on dictionary words. The PPK ID and PPK data are stored in the ipsec.secrets file, for example:

@west @east : PPKS "user1" "thestringismeanttobearandomstr"

The PPKS option refers to static PPKs. This experimental function uses one-time-pad-based Dynamic PPKs. Upon each connection, a new part of the one-time pad is used as the PPK. When used, that part of the dynamic PPK inside the file is overwritten with zeros to prevent re-use. If there is no more one-time-pad material left, the connection fails. See the ipsec.secrets(5) man page for more information.

Warning

The implementation of dynamic PPKs is provided as an unsupported Technology Preview. Use with caution.

7.3. Installing Libreswan

Before you can set a VPN through the Libreswan IPsec/IKE implementation, you must install the corresponding packages, start the ipsec service, and allow the service in your firewall.

Prerequisites

  • The AppStream repository is enabled.

Procedure

  1. Install the libreswan packages:

    # yum install libreswan
  2. If you are re-installing Libreswan, remove its old database files and create a new database:

    # systemctl stop ipsec
    # rm /etc/ipsec.d/*db
    # ipsec initnss
  3. Start the ipsec service, and enable the service to be started automatically on boot:

    # systemctl enable ipsec --now
  4. Configure the firewall to allow 500 and 4500/UDP ports for the IKE, ESP, and AH protocols by adding the ipsec service:

    # firewall-cmd --add-service="ipsec"
    # firewall-cmd --runtime-to-permanent

7.4. Creating a host-to-host VPN

You can configure Libreswan to create a host-to-host IPsec VPN between two hosts referred to as left and right using authentication by raw RSA keys.

Prerequisites

  • Libreswan is installed and the ipsec service is started on each node.

Procedure

  1. Generate a raw RSA key pair on each host:

    # ipsec newhostkey
  2. The previous step returned the generated key’s ckaid. Use that ckaid with the following command on left, for example:

    # ipsec showhostkey --left --ckaid 2d3ea57b61c9419dfd6cf43a1eb6cb306c0e857d

    The output of the previous command generated the leftrsasigkey= line required for the configuration. Do the same on the second host (right):

    # ipsec showhostkey --right --ckaid a9e1f6ce9ecd3608c24e8f701318383f41798f03
  3. In the /etc/ipsec.d/ directory, create a new my_host-to-host.conf file. Write the RSA host keys from the output of the ipsec showhostkey commands in the previous step to the new file. For example:

    conn mytunnel
        leftid=@west
        left=192.1.2.23
        leftrsasigkey=0sAQOrlo+hOafUZDlCQmXFrje/oZm [...] W2n417C/4urYHQkCvuIQ==
        rightid=@east
        right=192.1.2.45
        rightrsasigkey=0sAQO3fwC6nSSGgt64DWiYZzuHbc4 [...] D/v8t5YTQ==
        authby=rsasig
  4. After importing keys, restart the ipsec service:

    # systemctl restart ipsec
  5. Load the connection:

    # ipsec auto --add mytunnel
  6. Establish the tunnel:

    # ipsec auto --up mytunnel
  7. To automatically start the tunnel when the ipsec service is started, add the following line to the connection definition:

    auto=start

7.5. Configuring a site-to-site VPN

To create a site-to-site IPsec VPN, by joining two networks, an IPsec tunnel between the two hosts, is created. The hosts thus act as the end points, which are configured to permit traffic from one or more subnets to pass through. Therefore you can think of the host as gateways to the remote portion of the network.

The configuration of the site-to-site VPN only differs from the host-to-host VPN in that one or more networks or subnets must be specified in the configuration file.

Prerequisites

Procedure

  1. Copy the file with the configuration of your host-to-host VPN to a new file, for example:

    # cp /etc/ipsec.d/my_host-to-host.conf /etc/ipsec.d/my_site-to-site.conf
  2. Add the subnet configuration to the file created in the previous step, for example:

    conn mysubnet
         also=mytunnel
         leftsubnet=192.0.1.0/24
         rightsubnet=192.0.2.0/24
         auto=start
    
    conn mysubnet6
         also=mytunnel
         leftsubnet=2001:db8:0:1::/64
         rightsubnet=2001:db8:0:2::/64
         auto=start
    
    # the following part of the configuration file is the same for both host-to-host and site-to-site connections:
    
    conn mytunnel
        leftid=@west
        left=192.1.2.23
        leftrsasigkey=0sAQOrlo+hOafUZDlCQmXFrje/oZm [...] W2n417C/4urYHQkCvuIQ==
        rightid=@east
        right=192.1.2.45
        rightrsasigkey=0sAQO3fwC6nSSGgt64DWiYZzuHbc4 [...] D/v8t5YTQ==
        authby=rsasig

7.6. Configuring a remote access VPN

Road warriors are traveling users with mobile clients and a dynamically assigned IP address. The mobile clients authenticate using X.509 certificates.

The following example shows configuration for IKEv2, and it avoids using the IKEv1 XAUTH protocol.

On the server:

conn roadwarriors
    ikev2=insist
    # support (roaming) MOBIKE clients (RFC 4555)
    mobike=yes
    fragmentation=yes
    left=1.2.3.4
    # if access to the LAN is given, enable this, otherwise use 0.0.0.0/0
    # leftsubnet=10.10.0.0/16
    leftsubnet=0.0.0.0/0
    leftcert=gw.example.com
    leftid=%fromcert
    leftxauthserver=yes
    leftmodecfgserver=yes
    right=%any
    # trust our own Certificate Agency
    rightca=%same
    # pick an IP address pool to assign to remote users
    # 100.64.0.0/16 prevents RFC1918 clashes when remote users are behind NAT
    rightaddresspool=100.64.13.100-100.64.13.254
    # if you want remote clients to use some local DNS zones and servers
    modecfgdns="1.2.3.4, 5.6.7.8"
    modecfgdomains="internal.company.com, corp"
    rightxauthclient=yes
    rightmodecfgclient=yes
    authby=rsasig
    # optionally, run the client X.509 ID through pam to allow or deny client
    # pam-authorize=yes
    # load connection, do not initiate
    auto=add
    # kill vanished roadwarriors
    dpddelay=1m
    dpdtimeout=5m
    dpdaction=clear

On the mobile client, the road warrior’s device, use a slight variation of the previous configuration:

conn to-vpn-server
    ikev2=insist
    # pick up our dynamic IP
    left=%defaultroute
    leftsubnet=0.0.0.0/0
    leftcert=myname.example.com
    leftid=%fromcert
    leftmodecfgclient=yes
    # right can also be a DNS hostname
    right=1.2.3.4
    # if access to the remote LAN is required, enable this, otherwise use 0.0.0.0/0
    # rightsubnet=10.10.0.0/16
    rightsubnet=0.0.0.0/0
    fragmentation=yes
    # trust our own Certificate Agency
    rightca=%same
    authby=rsasig
    # allow narrowing to the server’s suggested assigned IP and remote subnet
    narrowing=yes
    # support (roaming) MOBIKE clients (RFC 4555)
    mobike=yes
    # initiate connection
    auto=start

7.7. Configuring a mesh VPN

A mesh VPN network, which is also known as an any-to-any VPN, is a network where all nodes communicate using IPsec. The configuration allows for exceptions for nodes that cannot use IPsec. The mesh VPN network can be configured in two ways:

  • To require IPsec.
  • To prefer IPsec but allow a fallback to clear-text communication.

Authentication between the nodes can be based on X.509 certificates or on DNS Security Extensions (DNSSEC).

You can use any regular IKEv2 authentication method for opportunistic IPsec, because these connections are regular Libreswan configurations, except for the opportunistic IPsec that is defined by right=%opportunisticgroup entry. A common authentication method is for hosts to authenticate each other based on X.509 certificates using a commonly shared certification authority (CA). Cloud deployments typically issue certificates for each node in the cloud as part of the standard procedure.

Important

Do not use PreSharedKey (PSK) authentication because one compromised host would result in group PSK secret being compromised as well.

You can use NULL authentication to deploy encryption between nodes without authentication, which protects only against passive attackers.

The following procedure uses X.509 certificates. You can generate these certificates by using any kind of CA management system, such as the Dogtag Certificate System. Dogtag assumes that the certificates for each node are available in the PKCS #12 format (.p12 files), which contain the private key, the node certificate, and the Root CA certificate used to validate other nodes' X.509 certificates.

Each node has an identical configuration with the exception of its X.509 certificate. This allows for adding new nodes without reconfiguring any of the existing nodes in the network. The PKCS #12 files require a "friendly name", for which we use the name "node" so that the configuration files referencing the friendly name can be identical for all nodes.

Prerequisites

  • Libreswan is installed, and the ipsec service is started on each node.
  • A new NSS database is initialized.

    1. If you already have an old NSS database, remove the old database files:

      # systemctl stop ipsec
      # rm /etc/ipsec.d/*db
    2. You can initialize a new database with the following command:

      # ipsec initnss

Procedure

  1. On each node, import PKCS #12 files. This step requires the password used to generate the PKCS #12 files:

    # ipsec import nodeXXX.p12
  2. Create the following three connection definitions for the IPsec required (private), IPsec optional (private-or-clear), and No IPsec (clear) profiles:

    # cat /etc/ipsec.d/mesh.conf
    conn clear
    	auto=ondemand 1
    	type=passthrough
    	authby=never
    	left=%defaultroute
    	right=%group
    
    conn private
    	auto=ondemand
    	type=transport
    	authby=rsasig
    	failureshunt=drop
    	negotiationshunt=drop
    	ikev2=insist
    	left=%defaultroute
    	leftcert=nodeXXXX
    	leftid=%fromcert 2
    	rightid=%fromcert
    	right=%opportunisticgroup
    
    conn private-or-clear
    	auto=ondemand
    	type=transport
    	authby=rsasig
    	failureshunt=passthrough
    	negotiationshunt=passthrough
    	# left
    	left=%defaultroute
    	leftcert=nodeXXXX 3
    	leftid=%fromcert
    	leftrsasigkey=%cert
    	# right
    	rightrsasigkey=%cert
    	rightid=%fromcert
    	right=%opportunisticgroup
1
The auto variable has several options:

You can use the ondemand connection option with opportunistic IPsec to initiate the IPsec connection, or for explicitly configured connections that do not need to be active all the time. This option sets up a trap XFRM policy in the kernel, enabling the IPsec connection to begin when it receives the first packet that matches that policy.

You can effectively configure and manage your IPsec connections, whether you use Opportunistic IPsec or explicitly configured connections, by using the following options:

The add option
Loads the connection configuration and prepares it for responding to remote initiations. However, the connection is not automatically initiated from the local side. You can manually start the IPsec connection by using the command ipsec auto --up.
The start option
Loads the connection configuration and prepares it for responding to remote initiations. Additionally, it immediately initiates a connection to the remote peer. You can use this option for permanent and always active connections.
2
The leftid and rightid variables identify the right and the left channel of the IPsec tunnel connection. You can use these variables to obtain the value of the local IP address or the subject DN of the local certificate, if you have configured one.
3
The leftcert variable defines the nickname of the NSS database that you want to use.
  1. Add the IP address of the network to the corresponding category. For example, if all nodes reside in the 10.15.0.0/16 network, and all nodes must use IPsec encryption:

    # echo "10.15.0.0/16" >> /etc/ipsec.d/policies/private
  2. To allow certain nodes, for example, 10.15.34.0/24, to work with and without IPsec, add those nodes to the private-or-clear group:

    # echo "10.15.34.0/24" >> /etc/ipsec.d/policies/private-or-clear
  3. To define a host, for example, 10.15.1.2, which is not capable of IPsec into the clear group, use:

    # echo "10.15.1.2/32" >> /etc/ipsec.d/policies/clear

    You can create the files in the /etc/ipsec.d/policies directory from a template for each new node, or you can provision them by using Puppet or Ansible.

    Note that every node has the same list of exceptions or different traffic flow expectations. Two nodes, therefore, might not be able to communicate because one requires IPsec and the other cannot use IPsec.

  4. Restart the node to add it to the configured mesh:

    # systemctl restart ipsec

Verification

  1. Open an IPsec tunnel by using the ping command:

    # ping <nodeYYY>
  2. Display the NSS database with the imported certification:

    # certutil -L -d sql:/etc/ipsec.d
    
    Certificate Nickname    Trust Attributes
                            SSL,S/MIME,JAR/XPI
    
    west                    u,u,u
    ca                      CT,,
  3. See which tunnels are open on the node:

    # ipsec trafficstatus
    006 #2: "private#10.15.0.0/16"[1] ...<nodeYYY>, type=ESP, add_time=1691399301, inBytes=512, outBytes=512, maxBytes=2^63B, id='C=US, ST=NC, O=Example Organization, CN=east'

Additional resources

7.8. Deploying a FIPS-compliant IPsec VPN

You can deploy a FIPS-compliant IPsec VPN solution with Libreswan. To do so, you can identify which cryptographic algorithms are available and which are disabled for Libreswan in FIPS mode.

Prerequisites

  • The AppStream repository is enabled.

Procedure

  1. Install the libreswan packages:

    # yum install libreswan
  2. If you are re-installing Libreswan, remove its old NSS database:

    # systemctl stop ipsec
    # rm /etc/ipsec.d/*db
  3. Start the ipsec service, and enable the service to be started automatically on boot:

    # systemctl enable ipsec --now
  4. Configure the firewall to allow 500 and 4500 UDP ports for the IKE, ESP, and AH protocols by adding the ipsec service:

    # firewall-cmd --add-service="ipsec"
    # firewall-cmd --runtime-to-permanent
  5. Switch the system to FIPS mode:

    # fips-mode-setup --enable
  6. Restart your system to allow the kernel to switch to FIPS mode:

    # reboot

Verification

  1. Confirm Libreswan is running in FIPS mode:

    # ipsec whack --fipsstatus
    000 FIPS mode enabled
  2. Alternatively, check entries for the ipsec unit in the systemd journal:

    $ journalctl -u ipsec
    ...
    Jan 22 11:26:50 localhost.localdomain pluto[3076]: FIPS Product: YES
    Jan 22 11:26:50 localhost.localdomain pluto[3076]: FIPS Kernel: YES
    Jan 22 11:26:50 localhost.localdomain pluto[3076]: FIPS Mode: YES
  3. To see the available algorithms in FIPS mode:

    # ipsec pluto --selftest 2>&1 | head -11
    FIPS Product: YES
    FIPS Kernel: YES
    FIPS Mode: YES
    NSS DB directory: sql:/etc/ipsec.d
    Initializing NSS
    Opening NSS database "sql:/etc/ipsec.d" read-only
    NSS initialized
    NSS crypto library initialized
    FIPS HMAC integrity support [enabled]
    FIPS mode enabled for pluto daemon
    NSS library is running in FIPS mode
    FIPS HMAC integrity verification self-test passed
  4. To query disabled algorithms in FIPS mode:

    # ipsec pluto --selftest 2>&1 | grep disabled
    Encryption algorithm CAMELLIA_CTR disabled; not FIPS compliant
    Encryption algorithm CAMELLIA_CBC disabled; not FIPS compliant
    Encryption algorithm SERPENT_CBC disabled; not FIPS compliant
    Encryption algorithm TWOFISH_CBC disabled; not FIPS compliant
    Encryption algorithm TWOFISH_SSH disabled; not FIPS compliant
    Encryption algorithm NULL disabled; not FIPS compliant
    Encryption algorithm CHACHA20_POLY1305 disabled; not FIPS compliant
    Hash algorithm MD5 disabled; not FIPS compliant
    PRF algorithm HMAC_MD5 disabled; not FIPS compliant
    PRF algorithm AES_XCBC disabled; not FIPS compliant
    Integrity algorithm HMAC_MD5_96 disabled; not FIPS compliant
    Integrity algorithm HMAC_SHA2_256_TRUNCBUG disabled; not FIPS compliant
    Integrity algorithm AES_XCBC_96 disabled; not FIPS compliant
    DH algorithm MODP1024 disabled; not FIPS compliant
    DH algorithm MODP1536 disabled; not FIPS compliant
    DH algorithm DH31 disabled; not FIPS compliant
  5. To list all allowed algorithms and ciphers in FIPS mode:

    # ipsec pluto --selftest 2>&1 | grep ESP | grep FIPS | sed "s/^.*FIPS//"
    {256,192,*128}  aes_ccm, aes_ccm_c
    {256,192,*128}  aes_ccm_b
    {256,192,*128}  aes_ccm_a
    [*192]  3des
    {256,192,*128}  aes_gcm, aes_gcm_c
    {256,192,*128}  aes_gcm_b
    {256,192,*128}  aes_gcm_a
    {256,192,*128}  aesctr
    {256,192,*128}  aes
    {256,192,*128}  aes_gmac
    sha, sha1, sha1_96, hmac_sha1
    sha512, sha2_512, sha2_512_256, hmac_sha2_512
    sha384, sha2_384, sha2_384_192, hmac_sha2_384
    sha2, sha256, sha2_256, sha2_256_128, hmac_sha2_256
    aes_cmac
    null
    null, dh0
    dh14
    dh15
    dh16
    dh17
    dh18
    ecp_256, ecp256
    ecp_384, ecp384
    ecp_521, ecp521

7.9. Protecting the IPsec NSS database by a password

By default, the IPsec service creates its Network Security Services (NSS) database with an empty password during the first start. To enhance security, you can add password protection.

Note

In the previous releases of RHEL up to version 6.6, you had to protect the IPsec NSS database with a password to meet the FIPS 140-2 requirements because the NSS cryptographic libraries were certified for the FIPS 140-2 Level 2 standard. In RHEL 8, NIST certified NSS to Level 1 of this standard, and this status does not require password protection for the database.

Prerequisites

  • The /etc/ipsec.d/ directory contains NSS database files.

Procedure

  1. Enable password protection for the NSS database for Libreswan:

    # certutil -N -d sql:/etc/ipsec.d
    Enter Password or Pin for "NSS Certificate DB":
    Enter a password which will be used to encrypt your keys.
    The password should be at least 8 characters long,
    and should contain at least one non-alphabetic character.
    
    Enter new password:
  2. Create the /etc/ipsec.d/nsspassword file that containins the password you have set in the previous step, for example:

    # cat /etc/ipsec.d/nsspassword
    NSS Certificate DB:_<password>_

    The nsspassword file use the following syntax:

    <token_1>:<password1>
    <token_2>:<password2>

    The default NSS software token is NSS Certificate DB. If your system is running in FIPS mode, the name of the token is NSS FIPS 140-2 Certificate DB.

  3. Depending on your scenario, either start or restart the ipsec service after you finish the nsspassword file:

    # systemctl restart ipsec

Verification

  1. Check that the ipsec service is running after you have added a non-empty password to its NSS database:

    # systemctl status ipsec
    ● ipsec.service - Internet Key Exchange (IKE) Protocol Daemon for IPsec
       Loaded: loaded (/usr/lib/systemd/system/ipsec.service; enabled; vendor preset: disable>
       Active: active (running)...

Verification

  • Check that the Journal log contains entries that confirm a successful initialization:

    # journalctl -u ipsec
    ...
    pluto[6214]: Initializing NSS using read-write database "sql:/etc/ipsec.d"
    pluto[6214]: NSS Password from file "/etc/ipsec.d/nsspassword" for token "NSS Certificate DB" with length 20 passed to NSS
    pluto[6214]: NSS crypto library initialized
    ...

Additional resources

7.10. Configuring an IPsec VPN to use TCP

Libreswan supports TCP encapsulation of IKE and IPsec packets as described in RFC 8229. With this feature, you can establish IPsec VPNs on networks that prevent traffic transmitted via UDP and Encapsulating Security Payload (ESP). You can configure VPN servers and clients to use TCP either as a fallback or as the main VPN transport protocol. Because TCP encapsulation has bigger performance costs, use TCP as the main VPN protocol only if UDP is permanently blocked in your scenario.

Prerequisites

Procedure

  1. Add the following option to the /etc/ipsec.conf file in the config setup section:

    listen-tcp=yes
  2. To use TCP encapsulation as a fallback option when the first attempt over UDP fails, add the following two options to the client’s connection definition:

    enable-tcp=fallback
    tcp-remoteport=4500

    Alternatively, if you know that UDP is permanently blocked, use the following options in the client’s connection configuration:

    enable-tcp=yes
    tcp-remoteport=4500

7.11. 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

  1. Edit the Libreswan configuration file in the /etc/ipsec.d/ directory of the connection that should use automatic detection of ESP hardware offload support.
  2. Ensure the nic-offload parameter is not set in the connection’s settings.
  3. If you removed nic-offload, restart the ipsec service:

    # systemctl restart ipsec

Verification

  1. Display the tx_ipsec and rx_ipsec counters of the Ethernet device the IPsec connection uses:

    # ethtool -S enp1s0 | egrep "_ipsec"
         tx_ipsec: 10
         rx_ipsec: 10
  2. Send traffic through the IPsec tunnel. For example, ping a remote IP address:

    # ping -c 5 remote_ip_address
  3. Display the tx_ipsec and rx_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

7.12. 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. Use the ethtool -k <interface_name> | grep "esp-hw-offload" command to verify whether each bond port 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

  1. 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.

  2. Reactivate the bond0 connection:

    # nmcli connection up bond0
  3. Edit the Libreswan configuration file in the /etc/ipsec.d/ directory of the connection that should use ESP hardware offload, and append the nic-offload=yes statement to the connection entry:

    conn example
        ...
        nic-offload=yes
  4. Restart the ipsec service:

    # systemctl restart ipsec

Verification

The verification methods depend on various aspects, such as the kernel version and driver. For example, certain drivers provide counters, but their names can vary. See the documentation of your network driver for details.

The following verification steps work for the ixgbe driver on Red Hat Enterprise Linux 8:

  1. Display the active port of the bond:

    # grep "Currently Active Slave" /proc/net/bonding/bond0
    Currently Active Slave: enp1s0
  2. Display the tx_ipsec and rx_ipsec counters of the active port:

    # ethtool -S enp1s0 | egrep "_ipsec"
         tx_ipsec: 10
         rx_ipsec: 10
  3. Send traffic through the IPsec tunnel. For example, ping a remote IP address:

    # ping -c 5 remote_ip_address
  4. Display the tx_ipsec and rx_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.

7.13. Configuring VPN connections with IPsec by using RHEL system roles

With the vpn system role, you can configure VPN connections on RHEL systems by using Red Hat Ansible Automation Platform. You can use it to set up host-to-host, network-to-network, VPN Remote Access Server, and mesh configurations.

For host-to-host connections, the role sets up a VPN tunnel between each pair of hosts in the list of vpn_connections using the default parameters, including generating keys as needed. Alternatively, you can configure it to create an opportunistic mesh configuration between all hosts listed. The role assumes that the names of the hosts under hosts are the same as the names of the hosts used in the Ansible inventory, and that you can use those names to configure the tunnels.

Note

The vpn RHEL system role currently supports only Libreswan, which is an IPsec implementation, as the VPN provider.

7.13.1. Creating a host-to-host VPN with IPsec by using the vpn RHEL system role

You can use the vpn system role to configure host-to-host connections by running an Ansible playbook on the control node, which configures all managed nodes listed in an inventory file.

Prerequisites

Procedure

  1. Create a playbook file, for example ~/playbook.yml, with the following content:

    - name: Host to host VPN
      hosts: managed-node-01.example.com, managed-node-02.example.com
      roles:
        - rhel-system-roles.vpn
      vars:
        vpn_connections:
          - hosts:
              managed-node-01.example.com:
              managed-node-02.example.com:
        vpn_manage_firewall: true
        vpn_manage_selinux: true

    This playbook configures the connection managed-node-01.example.com-to-managed-node-02.example.com by using pre-shared key authentication with keys auto-generated by the system role. Because vpn_manage_firewall and vpn_manage_selinux are both set to true, the vpn role uses the firewall and selinux roles to manage the ports used by the vpn role.

    To configure connections from managed hosts to external hosts that are not listed in the inventory file, add the following section to the vpn_connections list of hosts:

        vpn_connections:
          - hosts:
              managed-node-01.example.com:
              <external_node>:
                hostname: <IP_address_or_hostname>

    This configures one additional connection: managed-node-01.example.com-to-<external_node>

    Note

    The connections are configured only on the managed nodes and not on the external node.

  2. Optional: You can specify multiple VPN connections for the managed nodes by using additional sections within vpn_connections, for example, a control plane and a data plane:

    - name: Multiple VPN
      hosts: managed-node-01.example.com, managed-node-02.example.com
      roles:
        - rhel-system-roles.vpn
      vars:
        vpn_connections:
          - name: control_plane_vpn
            hosts:
              managed-node-01.example.com:
                hostname: 192.0.2.0 # IP for the control plane
              managed-node-02.example.com:
                hostname: 192.0.2.1
          - name: data_plane_vpn
            hosts:
              managed-node-01.example.com:
                hostname: 10.0.0.1 # IP for the data plane
              managed-node-02.example.com:
                hostname: 10.0.0.2
  3. 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.

  4. Run the playbook:

    $ ansible-playbook ~/playbook.yml

Verification

  1. On the managed nodes, confirm that the connection is successfully loaded:

    # ipsec status | grep <connection_name>

    Replace <connection_name> with the name of the connection from this node, for example managed_node1-to-managed_node2.

    Note

    By default, the role generates a descriptive name for each connection it creates from the perspective of each system. For example, when creating a connection between managed_node1 and managed_node2, the descriptive name of this connection on managed_node1 is managed_node1-to-managed_node2 but on managed_node2 the connection is named managed_node2-to-managed_node1.

  2. On the managed nodes, confirm that the connection is successfully started:

    # ipsec trafficstatus | grep <connection_name>
  3. Optional: If a connection does not successfully load, manually add the connection by entering the following command. This provides more specific information indicating why the connection failed to establish:

    # ipsec auto --add <connection_name>
    Note

    Any errors that may occur during the process of loading and starting the connection are reported in the /var/log/pluto.log file. Because these logs are hard to parse, manually add the connection to obtain log messages from the standard output instead.

Additional resources

  • /usr/share/ansible/roles/rhel-system-roles.vpn/README.md file
  • /usr/share/doc/rhel-system-roles/vpn/ directory

7.13.2. Creating an opportunistic mesh VPN connection with IPsec by using the vpn RHEL system role

You can use the vpn system role to configure an opportunistic mesh VPN connection that uses certificates for authentication by running an Ansible playbook on the control node, which will configure all the managed nodes listed in an inventory file.

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 IPsec Network Security Services (NSS) crypto library in the /etc/ipsec.d/ directory contains the necessary certificates.

Procedure

  1. Create a playbook file, for example ~/playbook.yml, with the following content:

    - name: Mesh VPN
      hosts: managed-node-01.example.com, managed-node-02.example.com, managed-node-03.example.com
      roles:
        - rhel-system-roles.vpn
      vars:
        vpn_connections:
          - opportunistic: true
            auth_method: cert
            policies:
              - policy: private
                cidr: default
              - policy: private-or-clear
                cidr: 198.51.100.0/24
              - policy: private
                cidr: 192.0.2.0/24
              - policy: clear
                cidr: 192.0.2.7/32
        vpn_manage_firewall: true
        vpn_manage_selinux: true

    Authentication with certificates is configured by defining the auth_method: cert parameter in the playbook. By default, the node name is used as the certificate nickname. In this example, this is managed-node-01.example.com. You can define different certificate names by using the cert_name attribute in your inventory.

    In this example procedure, the control node, which is the system from which you will run the Ansible playbook, shares the same classless inter-domain routing (CIDR) number as both of the managed nodes (192.0.2.0/24) and has the IP address 192.0.2.7. Therefore, the control node falls under the private policy which is automatically created for CIDR 192.0.2.0/24.

    To prevent SSH connection loss during the play, a clear policy for the control node is included in the list of policies. Note that there is also an item in the policies list where the CIDR is equal to default. This is because this playbook overrides the rule from the default policy to make it private instead of private-or-clear.

    Because vpn_manage_firewall and vpn_manage_selinux are both set to true, the vpn role uses the firewall and selinux roles to manage the ports used by the vpn role.

  2. 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.

  3. Run the playbook:

    $ ansible-playbook ~/playbook.yml

Additional resources

  • /usr/share/ansible/roles/rhel-system-roles.vpn/README.md file
  • /usr/share/doc/rhel-system-roles/vpn/ directory

7.14. Configuring IPsec connections that opt out of the system-wide crypto policies

Overriding system-wide crypto-policies for a connection

The RHEL system-wide cryptographic policies create a special connection called %default. This connection contains the default values for the ikev2, esp, and ike options. However, you can override the default values by specifying the mentioned option in the connection configuration file.

For example, the following configuration allows connections that use IKEv1 with AES and SHA-1 or SHA-2, and IPsec (ESP) with either AES-GCM or AES-CBC:

conn MyExample
  ...
  ikev2=never
  ike=aes-sha2,aes-sha1;modp2048
  esp=aes_gcm,aes-sha2,aes-sha1
  ...

Note that AES-GCM is available for IPsec (ESP) and for IKEv2, but not for IKEv1.

Disabling system-wide crypto policies for all connections

To disable system-wide crypto policies for all IPsec connections, comment out the following line in the /etc/ipsec.conf file:

include /etc/crypto-policies/back-ends/libreswan.config

Then add the ikev2=never option to your connection configuration file.

7.15. Troubleshooting IPsec VPN configurations

Problems related to IPsec VPN configurations most commonly occur due to several main reasons. If you are encountering such problems, you can check if the cause of the problem corresponds to any of the following scenarios, and apply the corresponding solution.

Basic connection troubleshooting

Most problems with VPN connections occur in new deployments, where administrators configured endpoints with mismatched configuration options. Also, a working configuration can suddenly stop working, often due to newly introduced incompatible values. This could be the result of an administrator changing the configuration. Alternatively, an administrator may have installed a firmware update or a package update with different default values for certain options, such as encryption algorithms.

To confirm that an IPsec VPN connection is established:

# ipsec trafficstatus
006 #8: "vpn.example.com"[1] 192.0.2.1, type=ESP, add_time=1595296930, inBytes=5999, outBytes=3231, id='@vpn.example.com', lease=100.64.13.5/32

If the output is empty or does not show an entry with the connection name, the tunnel is broken.

To check that the problem is in the connection:

  1. Reload the vpn.example.com connection:

    # ipsec auto --add vpn.example.com
    002 added connection description "vpn.example.com"
  2. Next, initiate the VPN connection:

    # ipsec auto --up vpn.example.com

Firewall-related problems

The most common problem is that a firewall on one of the IPsec endpoints or on a router between the endpoints is dropping all Internet Key Exchange (IKE) packets.

  • For IKEv2, an output similar to the following example indicates a problem with a firewall:

    # ipsec auto --up vpn.example.com
    181 "vpn.example.com"[1] 192.0.2.2 #15: initiating IKEv2 IKE SA
    181 "vpn.example.com"[1] 192.0.2.2 #15: STATE_PARENT_I1: sent v2I1, expected v2R1
    010 "vpn.example.com"[1] 192.0.2.2 #15: STATE_PARENT_I1: retransmission; will wait 0.5 seconds for response
    010 "vpn.example.com"[1] 192.0.2.2 #15: STATE_PARENT_I1: retransmission; will wait 1 seconds for response
    010 "vpn.example.com"[1] 192.0.2.2 #15: STATE_PARENT_I1: retransmission; will wait 2 seconds for
    ...
  • For IKEv1, the output of the initiating command looks like:

    # ipsec auto --up vpn.example.com
    002 "vpn.example.com" #9: initiating Main Mode
    102 "vpn.example.com" #9: STATE_MAIN_I1: sent MI1, expecting MR1
    010 "vpn.example.com" #9: STATE_MAIN_I1: retransmission; will wait 0.5 seconds for response
    010 "vpn.example.com" #9: STATE_MAIN_I1: retransmission; will wait 1 seconds for response
    010 "vpn.example.com" #9: STATE_MAIN_I1: retransmission; will wait 2 seconds for response
    ...

Because the IKE protocol, which is used to set up IPsec, is encrypted, you can troubleshoot only a limited subset of problems using the tcpdump tool. If a firewall is dropping IKE or IPsec packets, you can try to find the cause using the tcpdump utility. However, tcpdump cannot diagnose other problems with IPsec VPN connections.

  • To capture the negotiation of the VPN and all encrypted data on the eth0 interface:

    # tcpdump -i eth0 -n -n esp or udp port 500 or udp port 4500 or tcp port 4500

Mismatched algorithms, protocols, and policies

VPN connections require that the endpoints have matching IKE algorithms, IPsec algorithms, and IP address ranges. If a mismatch occurs, the connection fails. If you identify a mismatch by using one of the following methods, fix it by aligning algorithms, protocols, or policies.

  • If the remote endpoint is not running IKE/IPsec, you can see an ICMP packet indicating it. For example:

    # ipsec auto --up vpn.example.com
    ...
    000 "vpn.example.com"[1] 192.0.2.2 #16: ERROR: asynchronous network error report on wlp2s0 (192.0.2.2:500), complainant 198.51.100.1: Connection refused [errno 111, origin ICMP type 3 code 3 (not authenticated)]
    ...
  • Example of mismatched IKE algorithms:

    # ipsec auto --up vpn.example.com
    ...
    003 "vpn.example.com"[1] 193.110.157.148 #3: dropping unexpected IKE_SA_INIT message containing NO_PROPOSAL_CHOSEN notification; message payloads: N; missing payloads: SA,KE,Ni
  • Example of mismatched IPsec algorithms:

    # ipsec auto --up vpn.example.com
    ...
    182 "vpn.example.com"[1] 193.110.157.148 #5: STATE_PARENT_I2: sent v2I2, expected v2R2 {auth=IKEv2 cipher=AES_GCM_16_256 integ=n/a prf=HMAC_SHA2_256 group=MODP2048}
    002 "vpn.example.com"[1] 193.110.157.148 #6: IKE_AUTH response contained the error notification NO_PROPOSAL_CHOSEN

    A mismatched IKE version could also result in the remote endpoint dropping the request without a response. This looks identical to a firewall dropping all IKE packets.

  • Example of mismatched IP address ranges for IKEv2 (called Traffic Selectors - TS):

    # ipsec auto --up vpn.example.com
    ...
    1v2 "vpn.example.com" #1: STATE_PARENT_I2: sent v2I2, expected v2R2 {auth=IKEv2 cipher=AES_GCM_16_256 integ=n/a prf=HMAC_SHA2_512 group=MODP2048}
    002 "vpn.example.com" #2: IKE_AUTH response contained the error notification TS_UNACCEPTABLE
  • Example of mismatched IP address ranges for IKEv1:

    # ipsec auto --up vpn.example.com
    ...
    031 "vpn.example.com" #2: STATE_QUICK_I1: 60 second timeout exceeded after 0 retransmits.  No acceptable response to our first Quick Mode message: perhaps peer likes no proposal
  • When using PreSharedKeys (PSK) in IKEv1, if both sides do not put in the same PSK, the entire IKE message becomes unreadable:

    # ipsec auto --up vpn.example.com
    ...
    003 "vpn.example.com" #1: received Hash Payload does not match computed value
    223 "vpn.example.com" #1: sending notification INVALID_HASH_INFORMATION to 192.0.2.23:500
  • In IKEv2, the mismatched-PSK error results in an AUTHENTICATION_FAILED message:

    # ipsec auto --up vpn.example.com
    ...
    002 "vpn.example.com" #1: IKE SA authentication request rejected by peer: AUTHENTICATION_FAILED

Maximum transmission unit

Other than firewalls blocking IKE or IPsec packets, the most common cause of networking problems relates to an increased packet size of encrypted packets. Network hardware fragments packets larger than the maximum transmission unit (MTU), for example, 1500 bytes. Often, the fragments are lost and the packets fail to re-assemble. This leads to intermittent failures, when a ping test, which uses small-sized packets, works but other traffic fails. In this case, you can establish an SSH session but the terminal freezes as soon as you use it, for example, by entering the 'ls -al /usr' command on the remote host.

To work around the problem, reduce MTU size by adding the mtu=1400 option to the tunnel configuration file.

Alternatively, for TCP connections, enable an iptables rule that changes the MSS value:

# iptables -I FORWARD -p tcp --tcp-flags SYN,RST SYN -j TCPMSS --clamp-mss-to-pmtu

If the previous command does not solve the problem in your scenario, directly specify a lower size in the set-mss parameter:

# iptables -I FORWARD -p tcp --tcp-flags SYN,RST SYN -j TCPMSS --set-mss 1380

Network address translation (NAT)

When an IPsec host also serves as a NAT router, it could accidentally remap packets. The following example configuration demonstrates the problem:

conn myvpn
    left=172.16.0.1
    leftsubnet=10.0.2.0/24
    right=172.16.0.2
    rightsubnet=192.168.0.0/16
…

The system with address 172.16.0.1 have a NAT rule:

iptables -t nat -I POSTROUTING -o eth0 -j MASQUERADE

If the system on address 10.0.2.33 sends a packet to 192.168.0.1, then the router translates the source 10.0.2.33 to 172.16.0.1 before it applies the IPsec encryption.

Then, the packet with the source address 10.0.2.33 no longer matches the conn myvpn configuration, and IPsec does not encrypt this packet.

To solve this problem, insert rules that exclude NAT for target IPsec subnet ranges on the router, in this example:

iptables -t nat -I POSTROUTING -s 10.0.2.0/24 -d 192.168.0.0/16 -j RETURN

Kernel IPsec subsystem bugs

The kernel IPsec subsystem might fail, for example, when a bug causes a desynchronizing of the IKE user space and the IPsec kernel. To check for such problems:

$ cat /proc/net/xfrm_stat
XfrmInError                 0
XfrmInBufferError           0
...

Any non-zero value in the output of the previous command indicates a problem. If you encounter this problem, open a new support case, and attach the output of the previous command along with the corresponding IKE logs.

Libreswan logs

Libreswan logs using the syslog protocol by default. You can use the journalctl command to find log entries related to IPsec. Because the corresponding entries to the log are sent by the pluto IKE daemon, search for the “pluto” keyword, for example:

$ journalctl -b | grep pluto

To show a live log for the ipsec service:

$ journalctl -f -u ipsec

If the default level of logging does not reveal your configuration problem, enable debug logs by adding the plutodebug=all option to the config setup section in the /etc/ipsec.conf file.

Note that debug logging produces a lot of entries, and it is possible that either the journald or syslogd service rate-limits the syslog messages. To ensure you have complete logs, redirect the logging to a file. Edit the /etc/ipsec.conf, and add the logfile=/var/log/pluto.log in the config setup section.

Additional resources

7.16. 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

  1. Press the Super key, type Settings, and press Enter to open the control-center application.
  2. Select the Network entry on the left.
  3. Click the + icon.
  4. Select VPN.
  5. Select the Identity menu entry to see the basic configuration options:

    General

    Gateway — The name or IP 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

      networking vpn advanced options
      Warning

      When configuring an IPsec-based VPN connection using the gnome-control-center application, the Advanced dialog displays the configuration, but it does not allow any changes. As a consequence, users cannot change any advanced IPsec options. Use the nm-connection-editor or nmcli tools instead to perform configuration of the advanced properties.

      Identification

    • Domain — If required, enter the Domain Name.

      Security

    • Phase1 Algorithms — corresponds to the ike Libreswan parameter — enter the algorithms to be used to authenticate and set up an encrypted channel.
    • Phase2 Algorithms — corresponds to the esp Libreswan parameter — enter the algorithms to be used for the IPsec 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 the ikelifetime Libreswan parameter — how long the key used to encrypt the traffic will be valid.
    • Phase2 Lifetime — corresponds to the salifetime 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 the rightsubnet 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 the fragmentation Libreswan parameter — whether or not to allow IKE fragmentation. Valid values are yes (default) or no.
    • Enable Mobike — corresponds to the mobike 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 are no (default) or yes.
  6. Select the IPv4 menu entry:

    IPv4 Method

    • Automatic (DHCP) — Choose this option if the network you are connecting to uses a DHCP server to assign dynamic IP addresses.
    • Link-Local Only — Choose this option if the network you are connecting to does not have a DHCP server and you do not want to assign IP addresses manually. Random addresses will be assigned as per RFC 3927 with prefix 169.254/16.
    • Manual — Choose this option if you want to assign IP addresses manually.
    • DisableIPv4 is disabled for this connection.

      DNS

      In the DNS section, when Automatic is ON, switch it to OFF 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, when Automatic is ON, routes from DHCP are used, but you can also add additional static routes. When OFF, only static routes are used.

    • Address — Enter the IP address of a remote network or host.
    • Netmask — The netmask or prefix length of the IP address entered above.
    • Gateway — The IP 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.

  7. To configure IPv6 settings in a VPN connection, select the IPv6 menu entry:

    IPv6 Method

    • Automatic — Choose this option to use IPv6 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 from DHCPv6 directly to create a stateful configuration.
    • Link-Local Only — Choose this option if the network you are connecting to does not have a DHCP server and you do not want to assign IP addresses manually. Random addresses will be assigned as per RFC 4862 with prefix FE80::0.
    • Manual — Choose this option if you want to assign IP addresses manually.
    • DisableIPv6 is disabled for this connection.

      Note that DNS, Routes, Use this connection only for resources on its network are common to IPv4 settings.

  8. Once you have finished editing the VPN connection, click the Add button to customize the configuration or the Apply button to save it for the existing one.
  9. Switch the profile to ON to active the VPN connection.

Additional resources

  • nm-settings-libreswan(5)

7.17. 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

  1. Open a terminal, and enter:

    $ nm-connection-editor
  2. Click the + button to add a new connection.
  3. Select the IPsec based VPN connection type, and click Create.
  4. On the VPN tab:

    1. 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
    2. 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’s leftid parameter.

      nm connection editor vpn tab

    3. Optional: Configure additional settings by clicking the Advanced button. You can configure the following settings:

      • Identification

        • Domain — If required, enter the domain name.
      • Security

        • Phase1 Algorithms corresponds to the ike Libreswan parameter. Enter the algorithms to be used to authenticate and set up an encrypted channel.
        • Phase2 Algorithms corresponds to the esp Libreswan parameter. Enter the algorithms to be used for the IPsec 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 the ikelifetime Libreswan parameter. This parameter defines how long the key used to encrypt the traffic is valid.
        • Phase2 Lifetime corresponds to the salifetime Libreswan parameter. This parameter defines how long a security association is valid.
      • Connectivity

        • Remote network corresponds to the rightsubnet 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 the fragmentation Libreswan parameter and defines whether or not to allow IKE fragmentation. Valid values are yes (default) or no.
        • Enable Mobike corresponds to the mobike 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 are no (default) or yes.
  5. On the IPv4 Settings tab, select the IP assignment method and, optionally, set additional static addresses, DNS servers, search domains, and routes.

    IPsec IPv4 tab

  6. Save the connection.
  7. Close nm-connection-editor.
Note

When you add a new connection by clicking the + button, 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.

Additional resources

  • nm-settings-libreswan(5) man page on your system

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.

Important

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

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

  1. On the RHEL router in network A:

    1. 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 and local parameters set the public IP addresses of the remote and the local routers.

    2. 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.

    3. Configure the tun0 connection to use a manual IPv4 configuration:

      # nmcli connection modify tun0 ipv4.method manual
    4. 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"
    5. Enable the tun0 connection.

      # nmcli connection up tun0
    6. 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
  2. On the RHEL router in network B:

    1. 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 and local parameters set the public IP addresses of the remote and local routers.

    2. Set the IPv4 address to the tun0 device:

      # nmcli connection modify tun0 ipv4.addresses '10.0.1.2/30'
    3. Configure the tun0 connection to use a manual IPv4 configuration:

      # nmcli connection modify tun0 ipv4.method manual
    4. 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"
    5. Enable the tun0 connection.

      # nmcli connection up tun0
    6. 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:

    1. On Router A, ping 172.16.0.1:

      # ping 172.16.0.1
    2. 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.

Important

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

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

  1. On the RHEL router in network A:

    1. 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 and local parameters set the public IP addresses of the remote and the local routers.

      Important

      The gre0 device name is reserved. Use gre1 or a different name for the device.

    2. 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.

    3. Configure the gre1 connection to use a manual IPv4 configuration:

      # nmcli connection modify gre1 ipv4.method manual
    4. 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"
    5. Enable the gre1 connection.

      # nmcli connection up gre1
    6. 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
  2. On the RHEL router in network B:

    1. 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 and local parameters set the public IP addresses of the remote and the local routers.

    2. Set the IPv4 address to the gre1 device:

      # nmcli connection modify gre1 ipv4.addresses '10.0.1.2/30'
    3. Configure the gre1 connection to use a manual IPv4 configuration:

      # nmcli connection modify gre1 ipv4.method manual
    4. 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"
    5. Enable the gre1 connection.

      # nmcli connection up gre1
    6. 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

  1. From each RHEL router, ping the IP address of the internal interface of the other router:

    1. On Router A, ping 172.16.0.1:

      # ping 172.16.0.1
    2. 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.

Important

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

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

  1. On the RHEL router in network A:

    1. Create a bridge interface named bridge0:

      # nmcli connection add type bridge con-name bridge0 ifname bridge0
    2. 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
    3. 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
    4. 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 and local parameters set the public IP addresses of the remote and the local routers.

      Important

      The gretap0 device name is reserved. Use gretap1 or a different name for the device.

    5. 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.

    6. Configure that activating the bridge0 connection automatically activates the ports of the bridge:

      # nmcli connection modify bridge0 connection.autoconnect-slaves 1
    7. Active the bridge0 connection:

      # nmcli connection up bridge0
  2. On the RHEL router in network B:

    1. Create a bridge interface named bridge0:

      # nmcli connection add type bridge con-name bridge0 ifname bridge0
    2. 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
    3. 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
    4. 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 and local parameters set the public IP addresses of the remote and the local routers.

    5. Optional: Disable the Spanning Tree Protocol (STP) if you do not need it:

      # nmcli connection modify bridge0 bridge.stp no
    6. Configure that activating the bridge0 connection automatically activates the ports of the bridge:

      # nmcli connection modify bridge0 connection.autoconnect-slaves 1
    7. Active the bridge0 connection:

      # nmcli connection up bridge0

Verification

  1. On both routers, verify that the enp1s0 and gretap1 connections are connected and that the CONNECTION 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
  2. From each RHEL router, ping the IP address of the internal interface of the other router:

    1. On Router A, ping 192.0.2.2:

      # ping 192.0.2.2
    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

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.

Important

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 the kernel-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

  1. Add a new Ethernet connection profile to NetworkManager:

    # nmcli connection add con-name Example ifname enp1s0 type ethernet
  2. 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.

  3. Activate the Example connection:

    # nmcli connection up Example

Verification

  1. Display the status of the devices and connections:

    # nmcli device status
    DEVICE      TYPE      STATE      CONNECTION
    enp1s0      ethernet  connected  Example
  2. 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 on your system

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

  1. 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.

  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 the br0 connection.
    • ipv4.method disabled and ipv6.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 the destination-port <port_number> option to the command.

  3. Activate the br0 connection profile:

    # nmcli connection up br0
  4. 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 on your system

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

  1. Create the ~/vxlan10-bridge.xml file with the following content:

    <network>
     <name>vxlan10-bridge</name>
     <forward mode="bridge" />
     <bridge name="br0" />
    </network>
  2. Use the ~/vxlan10-bridge.xml file to create a new virtual network in libvirt:

    # virsh net-define ~/vxlan10-bridge.xml
  3. Remove the ~/vxlan10-bridge.xml file:

    # rm ~/vxlan10-bridge.xml
  4. Start the vxlan10-bridge virtual network:

    # virsh net-start vxlan10-bridge
  5. Configure the vxlan10-bridge virtual network to start automatically when the libvirtd 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 on your system

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 in libvirtd.

Procedure

  • To create a new VM and configure it to use the vxlan10-bridge network, pass the --network network:vxlan10-bridge option to the virt-install command when you create the VM:

    # virt-install ... --network network:vxlan10-bridge
  • To change the network settings of an existing VM:

    1. Connect the VM’s network interface to the vxlan10-bridge virtual network:

      # virt-xml VM_name --edit --network network=vxlan10-bridge
    2. Shut down the VM, and start it again:

      # virsh shutdown VM_name
      # virsh start VM_name

Verification

  1. 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
  2. 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 the vxlan10-bridge network, the corresponding vnet* device on the host appears as a port of the bridge.

  3. Use address resolution protocol (ARP) requests to verify whether VMs are in the same VXLAN:

    1. Start two or more VMs in the same VXLAN.
    2. 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 the arping utility.

Additional resources

  • virt-install(1) and virt-xml(1) man pages on your system
  • virsh(1) and arping(8) man pages on your system

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.

Warning

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

  1. If the wifi radio has been disabled in NetworkManager, enable this feature:

    # nmcli radio wifi on
  2. 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.

  3. 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.

  4. If the network requires static IP addresses:

    1. 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
    2. 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
  5. Re-activate the connection:

    # nmcli connection up Office

Verification

  1. 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.

  2. Ping a hostname or IP address:

    # *ping -c 3 example.com

Additional resources

  • nm-settings-nmcli(5) man page on your system

10.3. Connecting to a wifi network by using the GNOME system menu

You can use the GNOME system menu to connect to a wifi network. When you connect to a network for the first time, GNOME creates a NetworkManager connection profile for it. If you configure the connection profile to not automatically connect, you can also use the GNOME system menu to manually connect to a wifi network with an existing NetworkManager connection profile.

Note

Using the GNOME system menu to establish a connection to a wifi network for the first time has certain limitations. For example, you can not configure IP address settings. In this case first configure the connections:

Prerequisites

  • A wifi device is installed on the host.
  • The wifi device is enabled, if it has a hardware switch.

Procedure

  1. Open the system menu on the right side of the top bar.
  2. Expand the Wi-Fi Not Connected entry.
  3. Click Select Network:

    gnome select wifi
  4. Select the wifi network you want to connect to.
  5. Click Connect.
  6. If this is the first time you connect to this network, enter the password for the network, and click Connect.

Verification

  1. Open the system menu on the right side of the top bar, and verify that the wifi network is connected:

    gnome wifi connected

    If the network appears in the list, it is connected.

  2. Ping a hostname or IP address:

    # ping -c 3 example.com

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

  1. Press the Super key, type Wi-Fi, and press Enter.
  2. Click on the name of the wifi network you want to connect to.
  3. Enter the password for the network, and click Connect.
  4. If the network requires additional settings, such as static IP addresses or a security type other than WPA2 Personal:

    1. Click the gear icon next to the network’s name.
    2. 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.

    3. Configure IPv4 settings on the IPv4 tab, and IPv6 settings on the IPv6 tab.
    4. On the Security tab, select the authentication of the network, such as WPA3 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.

    5. Click Apply.

Verification

  1. Open the system menu on the right side of the top bar, and verify that the wifi network is connected:

    gnome wifi connected

    If the network appears in the list, it is connected.

  2. 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.

Note

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

  1. 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             --
    ...
  2. Start nmtui:

    # nmtui
  3. Select Edit a connection, and press Enter.
  4. Press the Add button.
  5. Select Wi-Fi from the list of network types, and press Enter.
  6. 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.

  7. Enter the network device name into the Device field.
  8. Enter the name of the Wi-Fi network, the Service Set Identifier (SSID), into the SSID field.
  9. Leave the Mode field set to its default, Client.
  10. 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.

  11. Fill the authentication type-related fields.
  12. If the Wi-Fi network requires static IP addresses:

    1. Press the Automatic button next to the protocol, and select Manual from the displayed list.
    2. Press the Show button next to the protocol you want to configure to display additional fields, and fill them.
  13. Press the OK button to create and automatically activate the new connection.

    nmtui wi fi dynamic IP
  14. Press the Back button to return to the main menu.
  15. Select Quit, and press Enter to close the nmtui application.

Verification

  1. 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.

  2. 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

  1. Open a terminal and enter:

    # nm-connection-editor
  2. Click the + button to add a new connection.
  3. Select the Wi-Fi connection type, and click Create.
  4. Optional: Set a name for the connection profile.
  5. 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.

  6. On the Wi-Fi tab, enter the service set identifier (SSID) in the SSID field.
  7. On the Wi-Fi Security tab, select the authentication type for the network, such as WPA3 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.

  8. Configure IPv4 settings on the IPv4 tab, and IPv6 settings on the IPv6 tab.
  9. Click Save.
  10. Close the Network Connections window.

Verification

  1. Open the system menu on the right side of the top bar, and verify that the wifi network is connected:

    gnome wifi connected

    If the network appears in the list, it is connected.

  2. 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.

Procedure

  1. Store your sensitive variables in an encrypted file:

    1. Create the vault:

      $ ansible-vault create vault.yml
      New Vault password: <vault_password>
      Confirm New Vault password: <vault_password>
    2. After the ansible-vault create command opens an editor, enter the sensitive data in the <key>: <value> format:

      pwd: <password>
    3. Save the changes, and close the editor. Ansible encrypts the data in the vault.
  2. 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.

  3. 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.

  4. 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

  1. Set the wifi security mode to wpa-eap, the Extensible Authentication Protocol (EAP) to peap, the inner authentication protocol to mschapv2, 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, and 802-1x.identity parameters in a single command.

  2. Optional: Store the password in the configuration:

    # nmcli connection modify wlp1s0 802-1x.password password
    Important

    By default, NetworkManager stores the password in plain text in the /etc/sysconfig/network-scripts/keys-connection_name file, which is readable only by the root 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 to 0x1. With this setting, on servers with the GNOME desktop environment or the nm-applet running, NetworkManager retrieves the password from these services. In other cases, NetworkManager prompts for the password.

  3. 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
    Note

    For security reasons, clients should validate the certiciate of the authenticator.

  4. Activate the connection profile:

    # nmcli connection up wlp1s0

Verification

  • Access resources on the network that require network authentication.

Additional resources

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.

Important

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

  1. Optional: Display the current regulatory domain settings:

    # iw reg get
    global
    country US: DFS-FCC
    ...
  2. 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 as DE for Germany or US for the United States of America.

  3. Set the regulatory domain:

    # setregdomain

Verification

  • Display the regulatory domain settings:

    # iw reg get
    global
    country DE: DFS-ETSI
    ...

Additional resources

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

  1. List the wifi devices to identify the one that should provide the access point:

    # nmcli device status | grep wifi
    wlp0s20f3    wifi   disconnected    --
  2. 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.

  3. Install the dnsmasq and NetworkManager-wifi packages:

    # yum install dnsmasq NetworkManager-wifi

    NetworkManager uses the dnsmasq service to provide DHCP and DNS services to clients of the access point.

  4. 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), is Example-Hotspot and uses the pre-shared key password.

  5. Optional: Configure the access point to support only WPA3:

    # nmcli connection modify Example-Hotspot 802-11-wireless-security.key-mgmt sae
  6. By default, NetworkManager uses the IP address 10.42.0.1 for the wifi device and assigns IP addresses from the remaining 10.42.0.0/24 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.

  7. Activate the connection profile:

    # nmcli connection up Example-Hotspot

Verification

  1. On the server:

    1. 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))
    2. Display the nftables rule set to ensure that NetworkManager enabled forwarding and masquerading for traffic from the 10.42.0.0/24 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
          }
      }
  2. On a client with a wifi adapter:

    1. 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
      ...
    2. Connect to the Example-Hotspot wireless network. See Managing Wi-Fi connections.
    3. 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 on your system

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.

12.1. How MACsec increases 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)
  • IPv4 and IPv6 traffic
  • 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. To change the pre-shared key, you must update the NM configuration on all network hosts that use MACsec.

A MACsec connection uses an Ethernet device, such as an Ethernet network card, VLAN, or tunnel device, as a parent. You can either set an IP configuration only on the MACsec device to communicate with other hosts only by 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, you can configure MACsec for two common scenarios:

  • Host-to-host
  • Host-to-switch and switch-to-other-hosts
Important

You can use MACsec only between hosts being in the same physical or virtual LAN.

12.2. Configuring a MACsec connection by using nmcli

You can use the nmcli utility to configure Ethernet interfaces to use MACsec. For example, you can create a MACsec connection between two hosts that are connected over Ethernet.

Procedure

  1. 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:

      1. Create a 16-byte hexadecimal CAK:

        # dd if=/dev/urandom count=16 bs=1 2> /dev/null | hexdump -e '1/2 "%04x"'
        50b71a8ef0bd5751ea76de6d6c98c03a
      2. Create a 32-byte hexadecimal CKN:

        # dd if=/dev/urandom count=32 bs=1 2> /dev/null | hexdump -e '1/2 "%04x"'
        f2b4297d39da7330910a74abc0449feb45b5c0b9fc23df1430e1898fcf1c4550
  2. On both hosts you want to connect over a MACsec connection:
  3. 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 and macsec.mka-ckn parameters. The values must be the same on every host in the MACsec-protected network.

  4. Configure the IP settings on the MACsec connection.

    1. Configure the IPv4 settings. For example, to set a static IPv4 address, network mask, default gateway, and DNS server to the macsec0 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'
    2. Configure the IPv6 settings. For example, to set a static IPv6 address, network mask, default gateway, and DNS server to the macsec0 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'
  5. Activate the connection:

    # nmcli connection up macsec0

Verification

  1. Verify that the traffic is encrypted:

    # tcpdump -nn -i enp1s0
  2. Optional: Display the unencrypted traffic:

    # tcpdump -nn -i macsec0
  3. Display MACsec statistics:

    # ip macsec show
  4. Display individual counters for each type of protection: integrity-only (encrypt off) and encryption (encrypt on)

    # ip -s macsec show

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. No netfilter 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.

Note

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:

MACVLANIPVLAN

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

  1. 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
  2. To assign an IPv4 or IPv6 address to the interface, enter the following command:

    # ip addr add dev IPVLAN_device IP_address/subnet_mask_prefix
  3. In case of configuring an IPVLAN device in L3 mode or L3S mode, make the following setups:

    1. 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.

    2. 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.

  4. To set an IPVLAN device active, enter the following command:

    # ip link set dev IPVLAN_device up
  5. 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, by 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.

Procedure

  1. 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
    ...
  2. 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
  3. 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 the enp1s0 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 on your system.

14.2. Temporarily configuring a device as unmanaged in NetworkManager

You can temporarily configure devices as unmanaged, for example, for testing purposes.

Procedure

  1. 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  --
    ...
  2. Set the enp1s0 device to the unmanaged 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 the enp1s0 device indicates that NetworkManager does not manage this device.

Additional resources

  • NetworkManager.conf(5) man page on your system

Chapter 15. Configuring the loopback interface by using nmcli

By default, NetworkManager does not manage the loopback (lo) interface. After creating a connection profile for the lo interface, you can configure this device by using NetworkManager. Some of the examples are as follows:

  • Assign additional IP addresses to the lo interface
  • Define DNS addresses
  • Change the Maximum Transmission Unit (MTU) size of the lo interface

Procedure

  1. Create a new connection of type loopback:

    # nmcli connection add con-name example-loopback type loopback
  2. Configure custom connection settings, for example:

    1. To assign an additional IP address to the interface, enter:

      # nmcli connection modify example-loopback +ipv4.addresses 192.0.2.1/24
      Note

      NetworkManager manages the lo interface by always assigning the IP addresses 127.0.0.1 and ::1 that are persistent across the reboots. You can not override 127.0.0.1 and ::1. However, you can assign additional IP addresses to the interface.

    2. To set a custom Maximum Transmission Unit (MTU), enter:

      # nmcli con mod example-loopback loopback.mtu 16384
    3. To set an IP address to your DNS server, enter:

      # nmcli connection modify example-loopback ipv4.dns 192.0.2.0

      If you set a DNS server in the loopback connection profile, this entry is always available in the /etc/resolv.conf file. The DNS server entry remains independent of whether or not the host roams between different networks.

  3. Activate the connection:

    # nmcli connection up example-loopback

Verification

  1. Display the settings of the lo interface:

    # ip address show lo
    
    1: lo: <LOOPBACK,UP,LOWER_UP> mtu 16384 qdisc noqueue state UNKNOWN group default qlen 1000
    
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00 inet 127.0.0.1/8 scope host lo valid_lft forever preferred_lft forever inet 192.0.2.1/24 brd 192.0.2.255 scope global lo valid_lft forever preferred_lft forever
    
    inet6 ::1/128 scope host
    valid_lft forever preferred_lft forever
  2. Verify the DNS address:

    # cat /etc/resolv.conf
    ...
    nameserver 192.0.2.0
    ...

Chapter 16. 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.

16.1. 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
    Note

    To configure a dummy interface without IPv4 and IPv6 addresses, set both the ipv4.method and ipv6.method parameters to disabled. 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 on your system

Chapter 17. 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.

Note

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.

17.1. 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

  1. Optional: Display the list of network connections:

    # nmcli connection show
    NAME    UUID                                  TYPE      DEVICE
    Example 7a7e0151-9c18-4e6f-89ee-65bb2d64d365  ethernet  enp1s0
    ...
  2. Set the ipv6.method parameter of the connection to disabled:

    # nmcli connection modify Example ipv6.method "disabled"
  3. Restart the network connection:

    # nmcli connection up Example

Verification

  1. 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.

  2. Verify that the /proc/sys/net/ipv6/conf/enp1s0/disable_ipv6 file now contains the value 1:

    # cat /proc/sys/net/ipv6/conf/enp1s0/disable_ipv6
    1

    The value 1 means that IPv6 is disabled for the device.

Chapter 18. 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.

18.1. 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

  1. Optional: Display the current hostname setting:

    # nmcli general hostname
    old-hostname.example.com
  2. Set the new hostname:

    # nmcli general hostname new-hostname.example.com
  3. 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:

    1. Restart all services that only read the hostname when the service starts:

      # systemctl restart <service_name>
    2. Active shell users must re-login for the changes to take effect.

Verification

  • Display the hostname:

    # nmcli general hostname
    new-hostname.example.com

18.2. 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

  1. Optional: Display the current hostname setting:

    # hostnamectl status --static
    old-hostname.example.com
  2. 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.

  3. The hostnamectl utility 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:

    1. Restart all services that only read the hostname when the service starts:

      # systemctl restart <service_name>
    2. Active shell users must re-login for the changes to take effect.

Verification

  • Display the hostname:

    # hostnamectl status --static
    new-hostname.example.com

Chapter 19. 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.

19.1. 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

  1. Create the /etc/NetworkManager/conf.d/dhcp-client.conf file with the following content:

    [main]
    dhcp=dhclient

    You can set the dhcp parameter to internal (default) or dhclient.

  2. If you set the dhcp parameter to dhclient, install the dhcp-client package:

    # yum install dhcp-client
  3. 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 on your system

19.2. 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

  1. Set the ipv4.dhcp-timeout and ipv6.dhcp-timeout properties. For example, to set both options to 30 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.

  2. 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 the autoconnect-retries property. The default is 4.
      • 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.
  3. 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 on your system

Chapter 20. Running dhclient exit hooks using NetworkManager a dispatcher script

You can use a NetworkManager dispatcher script to execute dhclient exit hooks.

20.1. 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 the root 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:

  1. The interface name of the device the operation happened on.
  2. 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 on your system

20.2. 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

  1. 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
  2. Set the root user as owner of the file:

    # chown root:root /etc/NetworkManager/dispatcher.d/12-dhclient-down
  3. Set the permissions so that only the root user can execute it:

    # chmod 0700 /etc/NetworkManager/dispatcher.d/12-dhclient-down
  4. Restore the SELinux context:

    # restorecon /etc/NetworkManager/dispatcher.d/12-dhclient-down

Additional resources

  • NetworkManager(8) man page on your system

Chapter 21. 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.

Note

Alternatively, if you require a specific order of DNS servers in /etc/resolv.conf, see Configuring the order of DNS servers.

21.1. 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

  1. 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
  2. Reload the NetworkManager service:

    # systemctl reload NetworkManager
    Note

    After you reload the service, NetworkManager no longer updates the /etc/resolv.conf file. However, the last contents of the file are preserved.

  3. Optional: Remove the Generated by NetworkManager comment from /etc/resolv.conf to avoid confusion.

Verification

  1. Edit the /etc/resolv.conf file and manually update the configuration.
  2. Reload the NetworkManager service:

    # systemctl reload NetworkManager
  3. 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

Chapter 22. 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.

22.1. 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 the dns parameter is not set:

      NetworkManager orders the DNS servers from different connections based on the ipv4.dns-priority and ipv6.dns-priority parameter in each connection.

      If you set no value or you set ipv4.dns-priority and ipv6.dns-priority to 0, NetworkManager uses the global default value. See Default values of DNS priority parameters.

    • dns=dnsmasq or dns=systemd-resolved:

      When you use one of these settings, NetworkManager sets either 127.0.0.1 for dnsmasq or 127.0.0.53 as nameserver entry in the /etc/resolv.conf file.

      Both the dnsmasq and systemd-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 and systemd-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:

    1. VPN connections
    2. Connection with an active default route. The active default route is the default route with the lowest metric.

Additional resources