Open Shortest Path First (OSPF)

- An interior router protocol used in larger networks.

- A routers that sees a change to its routing table or that detect a change in the network immediately sends a multicast update to all other router in the network.

- OSPF vs. RIP

1. OSPF sends only the part of the routing table that has changed in its transmission. RIP sends the full routing tables each time.
2. OSPF sends a multicast only when its information has changed. RIP sends thee routing table every 30 seconds.

- If more than one OSPF are, one area must be area 0.0.0.0(the backbone area).

- All areas must be adjacent to the backbone area. If they are not, virtual link must be configure to the backbone area.