Troubleshooting guide

Troubleshooting OSPF
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5. Check other OSPF routers on the network by repeating steps 1 to 4. Make sure
that OSPF is configured properly on all neighboring routers so that neighbor
relationships can be established.
Mismatched OSPF Parameters
The Hello or dead timers, E-bits (set for stub areas), N-bits that are set for
Not-So-Stubby Areas (NSSAs), area IDs, authentication types, or network mask
parameters may be mismatched. The values set for these parameters (except for
N-bits) should all be the same throughout an OSPF area, and, in some cases, the entire
OSPF network.
Follow these steps to set consistent parameters for the OSPF network:
1. To identify the OSPF neighbors of each router, use the show ip ospf neighbor
command in Privileged EXEC mode.
2. If the output does not list an expected neighbor, use the show ip ospf interface
command in Privileged EXEC mode on the router and its expected neighbor, as
shown in the following example:
RDN#show ip ospf interface
Examine the Hello and dead timer interval values configured on OSPF interfaces.
3. Compare the values configured for the timers on each router. If there is a
mismatch, reconfigure the timer values so that they are the same on the router and
its neighbor.
For example, to change the Hello timer interval to 5 on Ethernet interface 0, enter
the following commands:
RDN(config)#interface ethernet <n>
where:
n is the number of the ethernet interface.
RDN(config-if)#ip ospf hello-interval <seconds>
The ospf hello-interval value must be the same for all nodes on a specific
network. The default ospf hello-interval is 10 seconds.