OSPF stand for Open Shortest Path First .It is a link-state routing protocol which is used to find the best path between the source and the destination router using its own Shortest Path First. It is developed by Internet Engineering Task Force (IETF) as one of the Interior Gateway Protocol (IGP)
OSPF is a link-state routing protocol providing fast convergence and excellent scalability. Like all link-state protocols, OSPF is very efficient in its use of network bandwidth.
It is a network layer protocol which works on the protocol number 89 and uses AD value 110. OSPF uses multicast address 220.127.116.11 for normal communication and 18.104.22.168 for update to designated router(DR)/Backup Designated Router (BDR).
DR and BDR election
- DR Router have highest priority.
- If there is a tie in router priority then highest router I’d will be considered. First, highest loopback address is considered. If no loopback is configured then the highest active IP address on the interface of the router is considered.