Troubleshooting Ospf Faults - 3Com 8807 Configuration Manual

336 C 31: OSPF C
HAPTER
Troubleshooting OSPF
Faults
ONFIGURATION
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
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.
Execute the display ospf peer command to view peers.
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Execute the display ospf interface command to view OSPF information on
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the interface.
Check whether the physical connections and the lower layer protocol operate
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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.
If the physical link and the lower layer protocol are normal, check the OSPF
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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.)
Ensure that the dead timer on the same interface is at least four times the value
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of the Hello timer.
If the network type is broadcast, there must be at least one interface with a
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priority greater than zero.
If an area is set as the stub area, to which the routers are connected. The area
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on these routers must be also set as the stub area.
The same interface type should be adopted for the neighboring routers.
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If more than two areas are configured, at least one area should be configured
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as the backbone area (that is to say, the area ID is 0).
Ensure that the backbone area is connected to all other areas.
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The virtual links do not pass through the stub area.
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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.
If more than two areas are configured on a router, at least one area should be
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configured as the backbone area.
As shown in Figure 86: RTA and RTD are configured to belong to only one area,
whereas RTB (Area0 and Area1) and RTC (Area1 and Area 2) are configured to
belong to two areas. In which, RTB also belongs to area0, which is compliant with
the requirement. However, none of the areas to which RTC belongs is Area0.
Therefore, a virtual link should be set up between RTC and RTB. Ensure that Area2
and Area0 (backbone area) is connected.