If you are preparing for your CCNA or ICND2 certification exam for sure you are going to encounter OSPF. Open Shortest Path First (OSPF) is a better choice when you have a heterogeneous network, yes it’s a open standard routing protocol which over comes the major draw backs of Distance vector protocols like RIP 1 and RIP2. OSPF is a link state protocol, which can be quite useful on a large network with hundreds of routers.
Unlike Distance vector protocols OSPF will not exchange full route updates at short interval rather the routing updates are send once there is a change in routing topology. Using the Dijkstra algorithm,OSPF first constructs the shortest path tree and then the routing table is populated which results in best paths to the destination. Due to this behavior, OSPF is able to recalculate the routes very fast in case of topology changes or a failure in link occurred. One of the OSPF’s advantage is convergence occurs quite fast and its scalable. Currently OSPFv2 is used with IPv4 networks and IPv6 networks use OSPFv3. OSPF also supports Variable-Length Subnet Masking (VLSM) and Classless Inter-Domain-Routing (CIDR).
In upcoming post I will talk about how OSPF works? and I will compare it with RIP1 and RIP2