System information

Troubleshooting TCP/IP
Book Title
7-124
Table 7-12 outlines the problems that might cause this symptom and describes solutions to those
problems.
Table 7-12 OSPF: Routes Missing from Routing Table
Possible Problem Solution
OSPF routers not
establishing neighbors
Follow the procedures outlined in the section “OSPF: Routers Not Establishing
Neighbors” earlier in this chapter.
Routing information
from IGRP or RIP is
not redistributed correctly
into OSPF
Step 1 Check the router configuration using the show running-config privileged
exec command.
Step 2 Look for a redistribute router configuration command entry. Make sure
that redistribution is configured and that the subnets keyword is used
with the command.
The subnets keyword must be included when IGRP or RIP is
redistributed into OSPF; otherwise, only major routes (not subnet routes)
are redistributed.
Step 3 If the redistribute command is not present, or if the subnets keyword is
not specified, add or change the configuration using the following
commands:
C7000(config)#router ospf 100
C7000(config)#redistribute ospf subnets
No ABR is configured
in an area, isolating that
area from the OSPF
backbone
Step 1 Use the show running-config privileged exec command on OSPF routers
to verify that at least one ABR exists for the area. ABRs must belong to
area 0, the OSPF backbone, as well as to another area. Look for network
statements which indicate that the router is part of area 0.
To define the interfaces on which OSPF runs and to define the area ID for
those interfaces, use the network area router configuration command:
network address wildcard-mask area area-id
Syntax Description:
• address—IP address.
• wildcard-mask—IP-address-type mask that includes “don’t care” bits.
• area-id—Area that is to be associated with the OSPF address range. It
can be specified as either a decimal value or as an IP address. If you
intend to associate areas with IP subnets, you can specify a subnet
address as the area-id.
Step 2 If no ABR exists in an area, configure one where appropriate. Use the
network router configuration command.
For example, to configure OSPF process 100 to participate in the OSPF
backbone area, enter the following commands:
C4500(config)#router ospf 100
C4500(config-router)#network 192.21.3.7 0.0.0.255
area 0