3Com Switch 8800 Configuration Guide Chapter 19 OSPF Configuration
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19.5 Troubleshooting OSPF Faults Symptom 1: OSPF has been configured in accordance with the earlier-mentioned
steps, but OSPF on the router cannot run normally.
Solution: Check according to the following procedure.
Local troubleshooting: Check whether the protocol between two directly connected
routers is in normal operation. The normal sign is the peer state machine between the
two routers reaches the FULL state. (Note: On a broadcast or NBMA network, if the
interfaces for two routers are in DROther state, the peer state machines for the two
routers are in 2-way state, instead of FULL state. The peer state machine between
DR/BDR and all the other routers is in FULL state.
z Execute the display ospf peer command to view peers.
z Execute the display ospf interface command to view OSPF information on the
interface.
z Check whether the physical connections and the lower layer protocol operate
normally. You can execute the ping command to test. If the local router cannot
ping the peer router, it indicates that faults have occurred to the physical link and
the lower layer protocol.
z If the physical link and the lower layer protocol are normal, check the OSPF
parameters configured on the interface. The parameters should be the same
parameters configured on the router adjacent to the interface. The same area ID
should be used, and the networks and the masks should also be consistent. (The
p2p or virtually linked segment can have different segments and masks.)
z Ensure that the dead timer on the same interface is at least four times the value of
the hello timer.
z If the network type is NBMA, the peer must be manually specified, using the peer
ip-address command.
z If the network type is broadcast or NBMA, there must be at least one interface with
a priority greater than zero.
z If an area is set as the stub area, to which the routers are connected. The area on
these routers must be also set as the stub area.
z The same interface type should be adopted for the neighboring routers.
z If more than two areas are configured, at least one area should be configured as
the backbone area (that is to say, the area ID is 0).
z Ensure that the backbone area is connected to all other areas.
z The virtual links do not pass through the stub area.
Global troubleshooting: If OSPF cannot discover the remote routes yet in the case that
the above steps are correctly performed, proceed to check the following configurations.
z If more than two areas are configured on a router, at least one area should be
configured as the backbone area.