OpenBSD is another 4.4BSD-lite derived OS like so many others and anyone familiar with Linux and any other Unix will find themselves at home. It's most common use case is a a router, due to its very sophisticated networking features.

Using PPPeE

If you are using OpenBSD as a router, it is likely you will need to use PPPoE (the Point-to-Point Protocol over Ethernet as that is what many ISPs supply.

In the following example the ethernet cable from the fiber media converter is plugged into em0 network interface

# cat /etc/hostname.em0                                                        
mtu 1508 up

# cat /etc/hostname.pppoe0                                                     
inet 0.0.0.0 255.255.255.255 NONE \
pppoedev em0 \
authproto chap authname 'my-user-name' authkey 'my-secret' \
mtu 1500 \
up
dest 0.0.0.1
!/sbin/route add default -ifp pppoe0 0.0.0.1

# sh /etc/netstart

[Todo: add a section of pf firewall usage in a router, for the above]