OSPF (Open Shortest Path First)

• Router# conf terminal
• Router(config)# int e0
• Router(config_if)# ip add 192.168.10.10 255.255.255.0
• Router(config_if)# no shut
• Router(config_if)# exit
• Router(config)# int s0
• Router(config_if)# ip add 1.1.1.1 255.255.255.0
• Router(config_if)# no shut
• Router(config_if)# clock rate 6400
• Router(config_if)# router ospf 10 (10 represent the autonomous no which it prevent traffic from broad casting with each other)
• Router(config_router)# network 192.168.10.0 0.0.0.255 area 0
• Router(config_router)# network 1.0.0.0 0.0.0.255 area 0
• Router(config_router)# exit

Now do the configuration on router 2 as

• Router> enable
• Router# conf terminal
• Router(config)#int e0
• Router(config_if)# ip add 192.168.20.10 255.255.255.0
• Router(config_if)# no shut
• Router(config_if)# exit
• Router(config)# int s0
• Router(config_if)# ip add 1.1.1.2 255.255.255.0
• Router(config_if)# no shut
• Router(config_if)# clock rate 64000
• Router(config_if)# exit
• Router(config)# router ospf 10
• Router(config_router)# network 192.168.20.0 0.0.0.255 area 0
• Router(config_router)# network 1.0.0.0 0.0.0.255 area 0
• Router(config_router)# exit
• Router(config)# exit
• Router# exit

For Multiple Area

• Router(config)# router ospf 10
• Router(config_router)# network 192.168.20.0 0.0.0.255 area 0
• Router(config_router)# network 1.0.0.0 0.0.0.255 area 0
• Router(config-router)# network 192.168.10.0 0.0.0.255 area 1
• Router(config_router)# exit
• Router(config)# exit
• Router# exit

MORE:

• Default Routing
• Static Routing
• How to access a system on router 3
• RIP (routing information protocol) configuration 
• IGRP (Interior Gateway Routing Protocol)
• EIGRP (Enhanced Interior Gateway Routing Protocol)
• OSPF (Open Shortest Path First)