Chapter 4. IP Routing
Open Shortest Path First
Open Shortest Path First (OSPF) link-state routing protocol is designed to be more scalable and efficient than Routing Information Protocol (RIP). Some OSPF features you should be aware of are as follows:
- Runs on IP and uses protocol 89.
- Classless with variable-length subnet mask (VLSM) support.
- Uses multicasts (126.96.36.199—all shortest path first [SPF] routers; 188.8.131.52—Designated Router [DR]/Backup Designated Router [BDR]) for hellos and updates.
- Plain text and Message Digest Algorithm 5 (MD5) authentication available.
- Dijkstra's algorithm is used to produce a shortest-path tree for each destination. Link-state advertisements are used to build a database of the topology.
OSPF packet types