4.3 Configuring OSPF
4.3.1 Configuring OSPF on routers within a single area
In this section, you will learn how to configure OSPF on routers within a single area.

To configure OSPF, you must enable OSPF on the router and configure the router's network addresses and area information , according to the following steps:

  1. Enable OSPF on the router using the following command:

    router(config)#
    router ospf process-id

    The process ID is a process number on the local router. The process ID is used to identify multiple OSPF processes on the same router. The number can be any value between 1 and 65,535. You do not have to start numbering OSPF processes at 1. Most network administrators keep the same process ID throughout the entire AS. It is possible to run multiple OSPF processes on the same router, but is not recommended because it creates multiple database instances that add extra overhead to the router.
  2. Identify IP networks on the router, using the following command:

    router(config-router)#
    network address wildcard-mask area area-id

    For each network, you must identify the area to which the network belongs. The network value can be the network address, subnet, or the address of the interface. The router knows how to interpret the address by comparing the address to the wildcard mask. A wildcard mask is necessary because OSPF supports CIDR and VLSM, unlike RIPv1 and IGRP. The area argument is needed even when configuring OSPF in a single area. Again note that more than one IP network can belong to the same area.
Interactive Lab Activity (Flash, 371 kB)
  In this lab exercise, you will configure the SanJose1 router for OSPF in a single area. The Westasman router is already configured for OSPF.

You will first specify the OSPF process ID and then enter router configuration mode.

In router configuration mode, you will configure OSPF for specific networks in area 0.