When you configure OSPF network statements, IOS orders them most-specific to least-specific then does a top-to-bottom match of the interfaces. It doesn’t matter which order you put them in, the configuration will always be ordered with the longest prefix matches first. Lab time!
For both OSPF and EIGRP routers to become neighbors, their interface’s primary IP address must be on the same subnet. That statement is true. There is a subtle difference between the two, though.
This isn’t hard stuff at all. I’m sure there are a couple of cool tricks I don’t know yet, but let’s try anyway.
Here’s a story from last week with little of no teaching value. I got a call from one of our business units looking for some routing help. We don’t usually care about their production networks, but they were seeing some funky traceroutes, so I agreed to try and help them out.
I was studying via Google+ Hangout the other day with CJ and Rob, and one of the topics that came up was the idea of OSPFv2 advertising all loopbacks as 32-bit no matter what the configured mask is. I rarely use loopbacks outside of a lab and had no idea, so I set up a quick lab to see for myself. Sure enough! That’s exactly what I saw.
Corrections are always welcome.