Monitoring and Troubleshooting Frame Relay Operation

The two types of troubleshooting commands involved troubleshooting a configuration and troubleshooting a previously configured connection. Remember that you must execute all show commands in privileged EXEC mode.

Configuration Troubleshooting

Using the following command displays configuration information about serial devices:

 Router#show interfaces serial <interface_number> 

You will be able to tell what encapsulation is set, what DLCIs are being used, and so on. Using the next command shows configuration information regarding both static and dynamic Frame Relay mappings:

 Router#show frame-relay map 

It displays Layer 3 information, DLCIs, and the status of the link. This command is also useful for troubleshooting a previously working connection. If you get configuration information via Inverse-ARP and someone at the telco messes up a configuration, it could change how your router views mappings.

Troubleshooting a Previously Configured Connection

The following command displays LMI information for a specific interface:

 Router#show frame-relay lmi interface-type interface-number 

The interface information is optional, so you can get information regarding all interfaces.

The next command displays statistics about a specific DLCI on a specific interface:

 Router#show frame-relay pvc interface-type interface-number dlci 

The DLCI and interface are optional, so you can get all PVC information as well. The status is active if the circuit is ready for use, inactive if there is a problem reaching the remote router, and disabled if there is a problem reaching the telco switch. The following output shows PVC information from Serial 1/0.

 PVC Statistics for interface S1/0 (Frame Relay NNI) DLCI = 76, DLCI USAGE = SWITCHED, PVC STATUS = ACTIVE input pkts 0   output pkts 0   in bytes 0 out bytes 0   dropped pkts 0   in FECN pkts 0 in BECN pkts 0   out FECN pkts 0   out BECN pkts 0 in DE pkts 0   out DE pkts 0 outbcast pkts 0   outbcast bytes 0 pvc create time 0:00:01 last time pvc status changed 0:00:01 

The following command gives global Frame Relay traffic statistics since the last time the router has been rebooted or the statistics cleared:

 Router#show frame-relay traffic 

The next command gives header compression statistics for TCP/IP traffic. It requires that header compression be established:

 Router#show frame-relay ip tcp header-compression 

The interface status itself can give a lot of information regarding troubleshooting. If the interface is up but the line protocol is down, the problem is often related to receiving LMI packets from the switch. The wrong encapsulation or LMI type might be set or there might be other issues. The next command generates output specific to LMI reception and transmission:

 Router#debug frame-relay lmi 

You might also receive a message similar to "Encapsulation failed, no map entry link." In this case, the problem is that the router doesn't know where to forward the traffic. You might have an IP route, but the router doesn't have a link mapping the IP address to the DLCI. This problem occurs when you initially establish new manually configured routes, and with map statements configured via Inverse-ARP where the connection has failed.