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). Consider the following OSPF features:

• Runs on IP and uses protocol 89.

Classless with variable: Length subnet mask (VLSM) support.

Uses multicasts (224.0.0.5–all shortest path first [SPF] routers; 224.0.0.6: Designated Router [DR]/Backup Designated Router [BDR]) for hellos and updates.

• Plain text and Message Digest Algorithm 5 (MD5) authentication available. Null authentication is the default.

• 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. ...

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