Let's start with the spanish version debian-bridge-es, and translate it later.
Meanwhile:
Just a bridge:
apt-get install bridge-utils
ifconfig eth0 0.0.0.0 ifconfig eth1 0.0.0.0 brctl addbr br0 brctl addif br0 eth0 brctl addif br0 eth1
Bridge with IP:
ifconfig br0 192.168.0.2 netmask 255.255.255.0 up route add default gw 192.168.0.1 dev br0
Last update: 2006-09-21 (Rev 8545)