Troubleshooting guide

Troubleshooting OSPF
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4. Look in the show ip interface command output for a message for a specific
interface that is similar to the one in the following example:
ethernet 7/0 is up, line protocol is up
Internet address is 10.10.20.143/16
Broadcast address is 255.255.255.255
MTU 1500 bytes
Directed broadcast forwarding is disabled
Outgoing access list is not set
Inbound access list is not set
Outgoing qos list is not set
Proxy ARP is disabled
Split horizon is enabled
ICMP redirects are always sent
ICMP unreachables are always sent
ICMP mask replies are always sent
Router Discovery is disabled
5. To adjust the MTU size on the neighboring OSPF router to match the local MTU
size, Telnet into the neighboring OSPF router (which would be 102.2.2.2 using
the example in step 2).
6. On the OSPF interface on the neighboring OSPF router, configure the MTU size
to match the MTU size of the local OSPF router, as shown in the following
example:
router(config-if)#ip mtu 1500
7. To verify that the MTU size matches on both OSPF router interfaces, use the
debug ip ospf adj command in Privileged EXEC mode.
Resolving Missing Routes in Routing Table
When OSPF routes and networks are not advertised to other routers, routers in one
area do not receive routing information for other areas. Some hosts cannot
communicate with hosts in other areas, and routing table information is incomplete.