10.4. Configure 802.1Q VLAN Tagging Using the Command Line

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In Red Hat Enterprise Linux 7, the 8021q module is loaded by default. If necessary, you can make sure that the module is loaded by issuing the following command as root:
~]# modprobe --first-time 8021q
modprobe: ERROR: could not insert '8021q': Module already in kernel
To display information about the module, issue the following command:
~]$ modinfo 8021q
See the modprobe(8) man page for more command options.

10.4.1. Setting Up 802.1Q VLAN Tagging Using ifcfg Files

  1. Configure the parent interface in /etc/sysconfig/network-scripts/ifcfg-device_name, where device_name is the name of the interface:
  2. Configure the VLAN interface configuration in the /etc/sysconfig/network-scripts/ directory. The configuration file name should be the parent interface plus a . character plus the VLAN ID number. For example, if the VLAN ID is 192, and the parent interface is enp1s0, then the configuration file name should be ifcfg-enp1s0.192:
    If there is a need to configure a second VLAN, with for example, VLAN ID 193, on the same interface, enp1s0, add a new file with the name enp1s0.193 with the VLAN configuration details.
  3. Restart the networking service in order for the changes to take effect. As root issue the following command:
    ~]# systemctl restart network

10.4.2. Configure 802.1Q VLAN Tagging Using ip Commands

To create an 802.1Q VLAN interface on Ethernet interface enp1s0, with name VLAN8 and ID 8, issue a command as root as follows:
~]# ip link add link enp1s0 name enp1s0.8 type vlan id 8
To view the VLAN, issue the following command:
~]$ ip -d link show enp1s0.8
4: enp1s0.8@enp1s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP mode DEFAULT
     link/ether 52:54:00:ce:5f:6c brd ff:ff:ff:ff:ff:ff promiscuity 0
     vlan protocol 802.1Q id 8 <REORDER_HDR>
Note that the ip utility interprets the VLAN ID as a hexadecimal value if it is preceded by 0x and as an octal value if it has a leading 0. This means that in order to assign a VLAN ID with a decimal value of 22, you must not add any leading zeros.
To remove the VLAN, issue a command as root as follows:
~]# ip link delete enp1s0.8
To use multiple interfaces belonging to multiple VLANs, create locally enp1s0.1 and enp1s0.2 with the appropriate VLAN ID on top of a physical interface enp1s0:
~]# ip link add link enp1s0 name enp1s0.1 type vlan id 1
    ip link set dev enp1s0.1 up
~]# ip link add link enp1s0 name enp1s0.2 type vlan id 2
    ip link set dev enp1s0.2 up
Note that running a network sniffer on a physical device, you can capture the tagged frames reaching the physical device, even if no VLAN device is configured on top of enp1s0. For example:
tcpdump -nnei enp1s0 -vvv


VLAN interfaces created using ip commands at the command prompt will be lost if the system is shutdown or restarted. To configure VLAN interfaces to be persistent after a system restart, use ifcfg files. See Section 10.4.1, “Setting Up 802.1Q VLAN Tagging Using ifcfg Files”
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