Incorrect routing information
Symptom
OSPF cannot find routes to other areas.
Analysis
The backbone area must maintain connectivity to all other areas. If a router connects to more than one area, at least one area must be connected to the backbone. The backbone cannot be configured as a stub area.
In a Stub area, all routers cannot receive external routes, and all interfaces connected to the stub area must belong to the stub area.
Solution
Use the display ospf peer command to display neighbors.
Use the display ospf interface command to display OSPF interface information.
Use the display ospf lsdb command to display the LSDB to verify its integrity.
Use the display current-configuration configuration ospf command to display information about area configuration. If more than two areas are configured, at least one area is connected to the backbone.
In a stub area, all routers attached are configured with the stub command. In an NSSA area, all routers attached are configured with the nssa command.
If a virtual link is configured, use the display ospf vlink command to verify the state of the virtual link.