Configuring OSPF

Consider the topology given below –

Configuring OSPF

The initial IP configuration table is given below:

Devices Interface IP address
Router1 Se0/0/0 192.168.10.1
Fa0/0 10.0.0.1
Router2 Se0/0/0 192.168.10.2
Fa0/0 20.0.0.1
Switch1  N/A N/A
Switch2 N/A N/A
PC1 Fa0 10.0.0.2
PC2 Fa0 10.0.0.3
PC3 Fa0/0 20.0.0.2
PC4 Fa0/0 20.0.0.3

Configure IP address to router’s interfaces

Router>enable isused to enter the privileged exec mode.

Router#configure terminal is used to enter the global configuration mode.

Router(config)#hostname R1 is used to uniquely identify the router in the whole network.

R1(config)#interface s0/0/0 is used to enter the serial mode.

R1(config-if)#ip address 192.168.10.1 255.255.255.0 is used to configure an IP address in the serial interface.

R1(config-if)#clock rate 64000 is used to control the data flow.

R1(config-if)#no shutdown is used to make interface always up.

R1(config-if)#exit is used to return the previous mode.

R1(config)#interface f0/0 is used to enter the fastEthernet.

R1(config-if)# ip address  10.0.0.1 255.0.0.0 is used to configure an IP address in the fastEthernet interface.

R1(config-if)#no shutdown is used to make interface always up.

R1(config-if)#exit is used to move the global configuration mode.

Router1

On Router R1, give the following commands to configure hostname and IP address.

Configuring OSPF 1

Router2

On Router R2, give the following commands to configure hostname and IP address.

Configuring OSPF 2

Now when we ping from PC1 to PC3, it does not give any reply means there is no communication takes place between the PC1 and PC3.

Configuring OSPF 3

Configure the OSPF routing protocol

To enable OSPF, the following commands are used:

R1(config)# router ospf process_ID is used to enable OSPF routing protocol. Process_ID contains any positive integer from 1 to 65,535.

R1(config-router)# network IP_network address  [wildcard_mask] area [area number]

The above command allows us to specify interfaces which we want to include in the OSPF process.

The wildcard mask is used with the network address to filter the interfaces.

Router1

On Router1, we use following commands to configure OSPF:

Configuring OSPF 4

Router2

On Router2, we use the following commands to configure OSPF:

Configuring OSPF 5

Verifying OSPF Routing

To verify OSPF Routing, we use “show ip route” command on the routers (router1 or router2). If in the routing table there is the entry of the symbol “O” then we say that OSPF is enabled in the network.

Router1’s routing table is shown below:

Configuring OSPF 6

Router2’s routing table is shown below:

Configuring OSPF 7

After configuring OSPF, we again ping from PC1 to PC3, and then it replies with the ip address, bytes, time, and TTL, which means communication has been started between PC1 and PC2.

Configuring OSPF 8