Debian – How to transparently bridge Ethernet interfaces

Yesterday, I wrote a short note about VLAN interfaces. Today, I want to write a short entry on how to bridge Ethernet interfaces to keep things complete as I need to mention about creating ACCESS port to tag packets on desired interface.

Preparations

At first install utilities needed to configure the Ethernet bridge in Linux:

$ sudo apt-get install bridge-utils

Temporary solution

Create bridge br0 (name could be different):

$ sudo brctl addbr br0

To create ACCESS port on eth2 interface with VLAN 700 (available on eth1 interface) you need to bridge eth2 and eth1.700 interfaces:

$ sudo brctl addif br0 eth2
$ sudo brctl addif br0 eth1.700

Bring interface up:

$ sudo ifconfig br0 up

To list interfaces attached to the bridge execute command:

$ sudo brctl show br0
bridge name     bridge id               STP enabled     interfaces
br0             8000.000000000000       no              eth2
                                                        eth1.700

To list learned MAC addresses on the bridge execute command:

$ sudo brctl showmacs br0
port no mac addr                is local?       ageing timer
  3     08:00:27:2c:a4:69       no                 0.02
  3     08:00:27:a6:a6:fc       yes                0.00
  2     08:00:27:a7:37:c1       no                 0.53
  2     08:00:27:b9:55:fb       yes                0.00

To remove interface from the bridge execute command:

$ sudo brctl delif br0 eth9

To delete bridge execute commands:

$ sudo ifconfig br0 down
$ sudo brctl delbr br0

Permanent solution

To create bridge at the boot time you need edit /etc/network/interfaces file and add similar configuration:

auto br0
iface br0 inet manual
        bridge_ports eth1.700 eth2

Notes

Make sure that all used interfaces are UP and running.