If you searching tutorial on how to create bridged interface, maybe you’ll refer to Ubuntu documentation. Honestly, it’s hard. Maybe it works. But in my case, it doesn’t.

Nevermind, here I give you guide on how to do it in easier way.

First:

sudo apt-get install bridge-utils

It will create new interface called br0

Second:

sudo brctl addbr br0
sudo brctl addif br0 eth0 eth1

You can restart you interface by this command:

sudo /etc/init.d/networking restart

You also can setup bridged interface automatically on boot by adding this to /etc/network/interfaces:

auto br0
iface br0 inet static
address 192.168.1.10
netmask 255.255.255.0
broadcast 192.168.1.255
gateway 192.168.1.1
bridge_ports eth0 eth1

The important param is bridge_ports, which assign the ethernet port to bridge interface.