Listing 1. /etc/network/interfaces

auto lo
iface lo inet loopback
address 127.0.0.1
netmask 255.0.0.0

auto br0
iface br0 inet static
  address 10.0.0.253
  netmask 255.255.255.0
  pre-up ifconfig eth1 down
  pre-up ifconfig eth2 down
  pre-up brctl addbr br0
  pre-up brctl addif br0 eth1
  pre-up brctl addif br0 eth2
  pre-up ifconfig eth1 0.0.0.0
  pre-up ifconfig eth2 0.0.0.0
  post-down ifconfig eth1 down
  post-down ifconfig eth2 down
  post-down ifconfig br0 down
  post-down brctl delif br0 eth1
  post-down brctl delif br0 eth2
  post-down brctl delbr br0