What is OSPF and why to use it?
Open Shortest Path First (OSPF) is interior gateway protocol (IGP) that makes use of a link state routing (LSR) algorithm. OSPF supports complex networks with multiple routers and may be structured, or subdivided, into routing areas to simplify administration and optimize traffic and resource utilization. Areas are defined as the backbone area, stub area, not-so-stubby area, or a totally stubby area. Router types are defined as internal router (IR), area border router (ABR), backbone router (BR), or autonomous system boundary router (ASBR). In addition to the four router types, OSPF uses the terms designated router (DR) and backup designated router (BDR).
In the network below there are a total of three routers and three end-user computers. In real world deployments a network could have dozens or hundreds of routers or devices depending on the scale of the network. Regardless of the network complexity dynamic routing serves the same role in that its purpose is to share routes with other routers so devices know how to transverse networks and remote devices can return traffic back to the requester. Hence, the creation of dynamic routing.
Verify the configuration
Now that the configuration is finished lets verify our neighbors and routes. Using the show ip ospf neighbor and show ip route commands you can verify the remote routers to which your router has formed an adjacency and verify the expected routes are being advertised. Use the ping command to verify connectivity.
