OSPF Cisco

OSPF (Open Shortest Path First) is a routing protocol that is widely used in large enterprise networks. It is a link-state routing protocol that works by exchanging information about the network topology. Cisco is one of the leading providers of networking equipment, and its routers and switches support OSPF.

Configuration

Configuring OSPF on a Cisco router involves the following steps:

1. Enable OSPF on the router using the router ospf command.
2. Configure the router ID for the OSPF process using the router-id command.
3. Add the networks that are connected to the router using the network command.
4. Configure the area ID for the OSPF process using the area command.

Here is an example configuration for OSPF on a Cisco router:

router ospf 1
 router-id 1.1.1.1
 network 192.168.1.0 0.0.0.255 area 0
 network 172.16.1.0 0.0.0.255 area 1

In this example, OSPF is enabled on the router with process ID 1. The router ID is set to 1.1.1.1. The router is connected to two networks: 192.168.1.0/24 in area 0 and 172.16.1.0/24 in area 1.

Verification

Once OSPF is configured on a Cisco router, you can verify its operation using the show ip ospf command. This command displays information about the OSPF process, including the routers that are participating in the process and the routes that have been learned.

Here is an example output from the show ip ospf command:

Routing Process "ospf 1" with ID 1.1.1.1
 Start time: 00:03:43.052, Time elapsed: 00:00:44.888
 Supports only single TOS(TOS0) routes
 Supports opaque LSA
 SPF schedule delay 5 secs, Hold time between two SPFs 10 secs
 Minimum LSA interval 5 secs. Minimum LSA arrival 1 secs
 Number of external LSA 0. Checksum Sum 0x000000
 Number of opaque AS LSA 0. Checksum Sum 0x000000
 Number of DCbitless external and opaque AS LSA 0
 Number of DoNotAge external and opaque AS LSA 0
 Number of areas in this router is 2. 2 normal 0 stub 0 nssa
 External flood list length 0
SNIP...

This output shows that OSPF is running with process ID 1 and router ID 1.1.1.1. It also shows that the router is connected to two areas and that there are no external or opaque AS LSAs.

Conclusion

OSPF is an important routing protocol for large enterprise networks, and Cisco routers and switches support it. Configuring OSPF on a Cisco router involves enabling OSPF, configuring the router ID and network addresses, and verifying its operation using the show ip ospf command.