A long time ago, Packet Pushers ran an OSPF Design Part 1 show. That show went after the default design guides that network engineers have been reading for years, making the big point that you can scale a single OSPF area quite large indeed. But…that’s not the entire story about OSPF areas. Areas still have their use cases, and in this show (a long awaited part 2 that we did, seriously, get a lot of emails asking for), that’s what we get into.
What We Discuss
- What’s an area?
- What are the different types of areas?
- What’s an ABR? What’s an ASBR?
- What are the concerns with parallel ABRs (two ABRs between 0 and 1 for instance)?
- Why can’t you filter routes between OSPF routers in the same area?
- What’s the significance of the backbone area?
- Why must inter-area traffic traverse the backbone?
- Can you create discontiguous areas with the same area ID? Why doesn’t this break things?
- Use cases for OSPF areas.