brctl addbr br0
ifconfig br0 up
ifconfig eth0 0.0.0.0 promisc
brctl addif br0 eth0

#assming that eth0 was 192.168.0.100 with gateway 192.168.0.1

ifconfig br0 192.168.0.100
route del default
route add default gw 192.168.0.1 dev br0