# add a bridge device
brctl addbr br0
# add your eht device
brctl addif eth0
brctl addif eth1
echo 1 >; /proc/sys/net/ipv4/ip_forward
# bring up your eth0 and eth1
ifconfig eth0 0.0.0.0 up # since it don't need an address, so assigning it any address will do
ifconfig eth1 0.0.0.0 up # same thing here but eth1
# now bring up br0
#if your eth0 is your if connected to internet. with address 155.69.xxx.xxx
# your br0 should be assigned with that 155.69.xxx.xxx(any ip # will do, as long as it is same netmask)
ifconfig br0 155.69.xxx.xxx netmask xxx.xxx.xxx.xxx up
# remember to add gateway to your route
route add default gw xxx.xxx.xxx.xxx