Troubleshooting OSPF can sometimes be daunting, especially in a large internetwork. However, a routing problem with OSPF is no different than a routing problem with any other routing protocol; the cause will be one of the following:
Missing route information
Inaccurate route information
An examination of the route table is still the primary source of troubleshooting information. Using the show ip ospf database command to examine the various LSAs will also yield important information. For example, if a link is unstable, the LSA advertising it will change frequently. This condition is reflected in a sequence number that is conspicuously higher than that of the other LSAs. Another sign of instability is an LSA whose age ...