Enabling VLAN tagging on Redhat Linux

Posted on 2 mins read

I came across this one today, and am putting it here to document it ofr my own benefit. I needed a physical machine with one NIC to be able to have two different IP addresses on two different VLAN’s.

On Windows I am not sure if that is possible by default.

So how would you do it on Redhat Linux (taken from Howto: Configure Linux Virtual Local Area Network (VLAN))

This is the scenario. One network card with an IP of 192.168.10.1 (VLAN 10). I needed another interface on the same physical NIC with an IP address of 192.168.20.x (VLAN 20).

First you copy the network configuration

cp /etc/sysconfig/network-scripts/ifcfg-eth0 /etc/sysconfig/network-scripts/ifcfg-eth0.10

My original file looked like this:

DEVICE=eth0
ONBOOT=yes
BOOTPROTO=none
NETMASK=255.255.255.0
IPADDR=192.168.10.1
USERCTL=no
PEERDNS=yes
TYPE=Ethernet
IPV6INIT=no

I needed to add in the VLAN info and change the device name (add VLAN=yes)

DEVICE=eth0.10
ONBOOT=yes
VLAN=yes
BOOTPROTO=none
NETMASK=255.255.255.0
IPADDR=192.168.10.1
USERCTL=no
PEERDNS=yes
TYPE=Ethernet
IPV6INIT=no

I then copied the file again to my second interface

cp /etc/sysconfig/network-scripts/ifcfg-eth0.10 /etc/sysconfig/network-scripts/ifcfg-eth0.20

and changed the IP address and device name

DEVICE=eth0.20
ONBOOT=yes
VLAN=yes
BOOTPROTO=none
NETMASK=255.255.255.0
IPADDR=192.168.20.1
USERCTL=no
PEERDNS=yes
TYPE=Ethernet
IPV6INIT=no

I then removed the original IP address information from /etc/sysconfig/network-scripts/ifcfg-eth0

DEVICE=eth0
ONBOOT=yes
BOOTPROTO=none
USERCTL=no
PEERDNS=yes
TYPE=Ethernet
IPV6INIT=no

And restart the network service

service network restart

Of course the configuration has to be done as well on the switch side as well to allow the trunk of both VLAN’s

Switch#(config)interface Gi3/41
Switch#(config-if)no switchport mode access
Switch#(config-if)switchport mode trunk
Switch#(config-if)switchport trunk allowed vlan 10,20