3.3 Troubleshooting Routing Protocols  
  3.3.5 Troubleshooting OSPF configuration  
Open Shortest Path First (OSPF) is a link-state protocol. A link is an interface on a router. The state of the link is a description of that interface and of its relationship to its neighboring routers. For example, a description of the interface would include the IP address, the mask, the type of network to which it is connected, the routers connected to that network, and so on. This information forms a link-state database.

The majority of problems encountered with OSPF relate to the formation of adjacencies and the synchronization of the link-state databases. The show ip ospf neighbor command is useful for troubleshooting adjacency formation. OSPF configuration commands are shown in Figure .

Use the debug ip ospf events privileged EXEC command to display the following information about OSPF-related events:

  • Adjacencies
  • Flooding information
  • Designated router selection
  • Shortest path first (SPF) calculation

If a router configured for OSPF routing is not seeing an OSPF neighbor on an attached network, perform the following tasks:

  • Verify that both routers have been configured with the same IP mask, OSPF hello interval, and OSPF dead interval.
  • Verify that both neighbors are part of the same area.

To display information about each Open Shortest Path First (OSPF) packet received, use the debug ip ospf packet privileged EXEC command. The no form of this command disables debugging output.

The debug ip ospf packet command produces one set of information for each packet received. The output varies slightly, depending on which authentication is used.

 

Web Links

Troubleshooting OSPF

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