OpenBSD bridge port

To make a bridge port in OpenBSD. You have to do the following things

1. Create a file called /etc/hostname.bridge0,  and add the following line:
            add [interface name1]
            add [interface name2]
            up
2. In indiual interface files /etc/hostname.[interface name] either put IP or following line
        up media autoselect
   for IP write following line
        inet [ip address] [netmask] [broadcast address]

Source:
http://www.cyberciti.biz/faq/setting-up-a-network-bridge-in-openbsd/