OSPF Parameter Mismatches

In order for an OSPF neighbor relationship -- and consequently an OSPF adjacency -- to form, a number of values must match between the potential neighbors. Most (but not all) of these values are carried in the OSPF Hello packets that are exchanged between OSPF devices on a network link. We've covered these values in other lessons. This lesson will concentrate on the consequences of mismatched OSPF parameters as well as how to troubleshoot and fix these issues.

Must Match:HelloInterval, RouterDeadInterval, Area, Authentication (method and password), Stub Flag, and MTU

Must be compatible:Network Type

Must be unique:Router ID

Must match...sometimes: Network Mask :-)

In this lesson we're going to take a look at each of these potential mismatches. We'll look at the symptoms of each as well as how to troubleshoot (including extensive looks at debugging commands) as well as how to fix and (more importantly) how to avoid them in the first place.

This lesson has a lot of "real world" value as well as helping you prepare for a variety of Cisco certification exams from the CCNA to the Routing and Troubleshooting exams of the current CCNP track and even for CCIE lab preparation.