Chapter 2 Advanced Routing for FortiOS 5.0 : Open Shortest Path First (OSPF) : Troubleshooting OSPF
  
Troubleshooting OSPF
As with other dynamic routing protocols, OSPF has some issues that may need troubleshooting from time to time. For basic troubleshooting, see the Troubleshooting chapter.
The more common issues include:
Clearing OSPF routes from the routing table
Checking the state of OSPF neighbors
Passive interface problems
Timer problems
Authentication issues
DR and BDR election issues