3Com S7906E Configuration Manual page 709

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
1) Use the display ospf peer command to display neighbors.
2) Use the display ospf interface command to display OSPF interface information.
3) Use the display ospf lsdb command to display the Link State Database to check its integrity.
4) Display information about area configuration using the display current-configuration
configuration ospf command. If more than two areas are configured, at least one area is
connected to the backbone.
5) In a Stub area, all routers attached are configured with the stub command. In an NSSA area, all
interface connected to which are configured with the nssa command.
6) If a virtual link is configured, use the display ospf vlink command to check the state of the virtual
link.
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