System information

Troubleshooting TCP/IP 7-109
TCP/IP: Routing Not Functioning Properly on New Interface
TCP/IP: Routing Not Functioning Properly on New Interface
Symptom: A new interface is added to a router, but when routing is configured, it does not function
properly on the new interface.
Table 7-5 outlines the problems that might cause this symptom and describes solutions to those
problems.
Table 7-5 TCP/IP: Routing Not Functioning Properly on New Interface
Possible Problem Solution
Interface or LAN
protocol is down
Step 1 Use the show interfaces privileged exec command to see whether the
interface is “administratively down”:
Router#show interface serial 0
Serial0 is administratively down, line protocol is down
Hardware is HD64570
Internet address is 10.1.1.5 255.255.255.252
[...]
Step 2
If the interface is “administratively down,” bring up the interface using
the no shutdown interface configuration command. The following is an
example of performing the no shutdown command:
Router(config)#int serial0
Router(config-if)# no shutdown
Router(config-if)#
Step 3
Use the show interfaces command again to see whether the interface is
now up.
Step 4 If the interface is still down, there might be a hardware or media problem.
See the procedures outlined in the chapter that covers your media type.
Misconfigured or missing
network router
configuration command
Step 1 Use the show running-config privileged exec command to view the
router configuration.
Step 2 Make sure that there is a network router configuration command
specified for the network to which the interface belongs.
For example, if you assign the new interface IP address 192.168.52.42,
enter the following commands to enable RIP
1
on the interface:
c4500(config)#router rip
c4500(config-router)#network 192.168.52.0
Make sure that process IDs, addresses, and other variables are properly specified
for the routing protocol you are using. For more information, refer to the
Cisco IOS configuration guides and command references.