interface Loopback0
 ip address 1.1.1.1 255.255.255.0
!
interface Ethernet0/0
 ip address 192.168.12.1 255.255.255.0

router ospf 1
 router-id 1.1.1.1
 network 1.1.1.0 0.0.0.255 area 0
 network 192.168.12.0 0.0.0.255 area 0