System information

Troubleshooting TCP/IP 7-125
OSPF: Routes Missing from Routing Table
Interface network type
mismatch on Frame
Relay WAN
In an OSPF Frame Relay environment, if one end of the link is a multipoint
interface and the other end is a point-to-point interface, by default the multipoint
interface will advertise the link as a non-broadcast network and the point-to-point
interface will advertise the link as a point-to-point network. This creates a conflict
in the link-state database and can prevent routing information from being learned
properly.
Step 1 Check each router interface on each side of the link to see whether the
network types are mismatched. Use the show ip ospf interface privileged
exec command to check the network type configured for the interface.
Following is an example of the output from the show ip ospf interface
command:
Ethernet0 is up, line protocol is up
Internet Address 192.168.52.14 255.255.255.0, Area 0
Process ID 1, Router ID 192.168.52.14,
Network Type BROADCAST, Cost: 10
[...]
In this example, the network type is broadcast.
Step 2 Change the point-to-point interface to a multipoint interface by
configuring subinterfaces, or change the network type of the
point-to-point interface to broadcast using the ip ospf network
broadcast interface configuration command.
The following example sets your OSPF network as a broadcast network:
interface serial 0
ip address 160.89.77.17 255.255.255.0
ip ospf network broadcast
encapsulation frame-relay
For information on configuring subinterfaces, see the Cisco IOS configuration
guides.
Area is configured
as a stub area
Route redistribution is not possible in OSPF stub areas. No external routes are
advertised into a stub area, and if the area area-id stub no-summary router
configuration command is used, no summary routes (inter-area routes) will be
advertised into the stub area.
Step 1 If you want summary routes to be advertised into the stub area, but you do
not see them in the routing table, use the show running-config privileged
exec command to view the router configuration.
Step 2 Look for an area area-id stub no-summary command entry. If this
command is present, disable it by entering the following commands:
C4500(config)#router ospf 100
C4500(config-router)#no area 1 stub no-summary
This disables the no-summary keyword and keeps the router configured
as a stub.
Step 3 To advertise external routes into the area, you must configure the area as a
non-stub. Make certain that all routers in the area are reconfigured as
non-stub routers.
Possible Problem Solution