Configuring OSPF (Open Shortest Path First) protocol to provide routing information between the routers is simple process. OSPF is link state protocol which provides partial update to routers instead of sending the entire routing table from one router to another. It uses cost based metric with administrative distance of 110. It sends the entire routing table when you configure first time and periodically sends the new updates only. It provides loop free topology, fast convergence, and supports classless routing (CIDR).
Unlike, RIPv2, when you configuring OSPF, you need to specify process ID, wildcard mask and area. Process ID is local router ID and does not have any significant meaning to the other routers. Wildcard mask is reversed subnet mask of the network, for example if the subnet mask is 255.255.255.0, the wild-card will be 0.0.0.255. Area is way of administratively grouping routers together.
Use the commands below to configure a OSPF on a Cisco router.
R01#conf t Go into router config mode
Enter configuration commands, one per line. End with CNTL/Z.
R01(config)#do show ip route connected Show directly connected networks to advertise
C 10.1.1.0/24 is directly connected, FastEthernet0/0 Directly connected network
C 192.168.1.0/24 is directly connected, FastEthernet0/1 Directly Connected network
R01(config)#router ospf 1 Initiate OSPF configuration
R01(config-router)#network 10.1.1.0 0.0.0.255 area 0 Configure network(s) to be advertised
R01(config-router)#network 192.168.1.0 0.0.0.255 area 0
Use this command to view neighboring routers advertising OSPF:
R02#show ip ospf neighbor
Neighbor ID Pri State Dead Time Address Interface
192.168.1.10 1 FULL/DR 00:00:38 10.1.1.2 FastEthernet0/0