324 CHAPTER 28: OSPF CONFIGURATION
3 Ping the neighbor router’s IP address to check connectivity.
4 Check OSPF timers. The neighbor dead interval on an interface must be at least 
four times the hello interval.
5 On an NBMA network, using the peer ip-address command to specify the 
neighbor manually is required.
6 On an NBMA or a broadcast network, at least one connected interface must have 
a router priority higher than 0.
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.