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 (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.
  • 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

  • Type ...

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