OSPF Routing: Mandatory Commands

Router(config)#router ospf 123 Router(config-router)#

Turns on OSPF process number 123. The process ID is any value between 165535. The process ID is not related to the OSPF area
Router(config-router)#network 172.16.10.0 0.0.0.255 area 0
OSPF advertises interfaces, not networks. Uses the wildcard mask to determine which interfaces to advertise. Read this line to say: Any interface with an address of 172.16.10.x is to be put into Area 0

Note:

The process ID number of one router does not have to match the process ID number of any other router. Unlike Interior Gateway Routing Protocol (IGRP) or Enhanced IGRP (EIGRP), matching this number across all routers does not ensure network adjacencies will form.