Jorge Martinez de Salinas

As you may already know you can set up a linux box to work as a bridge. Suppose you want to bridge eth0 and eth1 interfaces. The steps are these:

# yum install bridge-utils
# brctl addbr br0
# brctl addif br0 eth0
# brctl addif br0 eth1
# brctl stp br0 on

These changes are not permanent. It you want to maintain them between reboots you have to edit some files:

1. Create /etc/sysconfig/network-scripts/ifcfg-br0 with your favourite editor.
2. Add the following lines to the file:

DEVICE=br0
TYPE=Bridge
STP=on
BOOTPROTO=none
ONBOOT=yes
IPADDR=10.0.0.2
NETMASK=255.255.255.0

3. Save the file.
4. Open the files /etc/sysconfig/network-scripts/ifcfg-eth0 and /etc/sysconfig/network-scripts/ifcfg-eth1
5. Add the following line to both files:

BRIDGE=br0

That’s it. Pretty easy huh?

Note1: a bridge doesn’t need an IP address. However you can always assign one for management purposes.

Note2: I’m using Centos 5.3. The configuration files on other distributions may vary. For example on Ubuntu the network configuration is stored on /etc/network/interfaces.