Slacy’s Blog

So, you want to switch eth0 from a ‘direct’ network connection to using a software bridge? Ok, here’s your 30 second guide. If you’re using DHCP, make your /etc/network/interfaces look like this:

# This file describes the network interfaces available on your system
# and how to activate them. For more information, see interfaces(5).

# The loopback network interface
auto lo
iface lo inet loopback

auto br0
iface br0 inet dhcp
# Ports you want to add to your bridge
bridge_ports eth0
# Time to wait before loading the bridge
bridge_maxwait 0

And then reboot your machine or run “/etc/init.d/networking restart”. Voila. All your traffic now goes through the software bridge.

Background: This is useful for when you want to run multiple virtual machines, and give them all independent access to the network. The virtual machines need virtual interfaces, and therefore, all the interfaces (both the virtual ones and the ‘real’ eth0) have to go through the bridge and out to the network. So, once you’ve bridged eth0, its easy enough to add virtual interfaces (tap/tun) and use those.