OSPF (Open Shortest Path First) is a popular interior gateway protocol (IGP) used for routing within an autonomous system (AS) in large enterprise networks and service provider networks. OSPF is a link-state protocol that allows routers to exchange information about the topology of the network and to compute the shortest path to each destination network based on this information.

OSPF uses a hierarchical network design with areas to reduce the size of the routing table and to improve scalability and performance. Each area is assigned a unique identifier and routers within an area only need to maintain a summary of the networks outside the area, which reduces the amount of routing information that needs to be exchanged.

OSPF also supports multiple paths to the same destination network, which allows for load balancing and redundancy. OSPF path selection is based on a metric called cost, which is calculated based on the bandwidth of the link. OSPF also supports authentication to ensure the security of the routing information.

Hhere’s an example configuration for OSPF on a network:

Determine the network topology and assign each router a unique Router ID (RID). In this example, we’ll use the following topology:

            |          |
[R1]--------+          +--------[R4]
            |          |

We’ll assign the following RIDs:


Enable OSPF on each router by configuring the router ID and the networks to be advertised. For example, on R1:

router ospf 1
ospf router-id
network area 0
network area 0

This configures OSPF for process ID 1, sets the router ID to, and advertises the networks and in area 0.

Repeat step 2 for each router, changing the router ID and the networks to be advertised as appropriate.

Verify that OSPF is running correctly by checking the OSPF neighbor table on each router:

show ip ospf neighbor

This should show the neighboring routers and their state.

(Optional) Fine-tune the OSPF configuration by adjusting parameters such as the hello and dead intervals, the OSPF network type (e.g., broadcast, point-to-point), and the cost of interfaces.

This is just a basic example, and there are many other options and considerations when configuring OSPF on a network.