The Everything Feed - All Packet Pushers Pods N4N038: Well Actually 02 – OSPF Multi-Area and LSA Types
Sep 15, 2025
Listener feedback sparks a deep dive into OSPF multi-area deployments and the intricacies of Link State Advertisements (LSAs). The discussion highlights the challenges and advantages of multi-area configurations versus single-area setups. Various LSA types are explored, particularly Types 1, 2, 3, and the unique Type 7 from NSSA. Historical practices and personal experiences from the speakers add depth to the conversation, while emphasizing the importance of audience engagement and understanding in networking.
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Prefer Single-Area OSPF For Simplicity
- Keep OSPF simple when possible by using a single area (Area 0) for small modern networks.
- Favor simplicity unless you need summarization or other multi-area features that justify added complexity.
Metro Multi-Area OSPF With SVI Summaries
- Hensley described a small metro network using multi-area OSPF with SVIs per switch and Area 0 on building interconnects.
- He summarized contiguous building IP blocks at ABRs and used stub areas and NSSA when needed for external connectivity.
Summarization Requires Multi-Area And Contiguous IPs
- Multi-area OSPF enables route summarization because you can only summarize at area borders, not inside an area.
- Summarization requires contiguous addressing, so address plan quality directly affects multi-area usefulness.