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This chapter discusses troubleshooting procedures for connectivity problems related to Frame Relay links. The sections in this chapter describe specific Frame Relay symptoms, the problems that are likely to cause each symptom, and the solutions to those problems.
Symptom: Connections over a Frame Relay link fail. The output of the show interfaces serial EXEC command shows that the interface and line protocol are down or that the interface is up and the line protocol is down.
Table 16-1 outlines the problems that might cause this symptom and describes solutions to those problems.
| Possible Problem | Solution |
|---|---|
| Cabling, hardware, or carrier problem | Perform these steps for the local and remote router.
Step 1 Use the show interfaces serial command to see if the interface and line protocol are up. Step 2 If the interface and line protocol are down, check the cable to make sure it is a DTE serial cable. Make sure cables are securely attached. Step 3 If the cable is correct, try moving it to a different port. If that port works, then the first port is defective. Replace either the card or the router. Step 4 If the cable doesn't work on the second port, try replacing the cable. If it still doesn't work, there might be a problem with the DCE. Contact your carrier about the problem. For detailed information on troubleshooting serial lines, refer to the "Troubleshooting Serial Line Problems" chapter. |
| LMI type mismatch | Step 1 Use the show interfaces serial command to check the state of the interface.
Step 2 If the output shows the interface is up but the line protocol is down, use the show frame-relay lmi EXEC command to see which LMI type is configured on the Frame Relay interface. Step 3 Make sure that the LMI type is the same for all devices in the path from source to destination. Use the frame-relay lmi-type {ansi | cisco | q933a} interface configuration command to change the LMI type on the router. |
| Keepalives not being sent | Step 1 Enter the show interfaces command to find out if keepalives are configured. If you see a line that says "keepalives not set," keepalives are not configured.
Step 2 Use the keepalive seconds interface configuration command to configure keepalives. The default value for this command is 10 seconds. |
| Encapsulation mismatch | Step 1 When connecting Cisco devices with non-Cisco devices, you must use IETF encapsulation on both devices. Check the encapsulation type on the Cisco device with the show frame-relay map EXEC command.
Step 2 If the Cisco device is not using IETF encapsulation, use the encapsulation frame-relay ietf interface configuration command to configure IETF encapsulation on the Cisco Frame Relay interface. For information on viewing or changing the configuration of the non-Cisco device, refer to the vendor documentation. |
| DLCI inactive or deleted | Step 1 Use the show frame-relay pvc EXEC command to view the status of the interface's PVC.
Step 2 If the output shows that the PVC is inactive or deleted, there is a problem along the path to the remote router. Check the remote router or contact your carrier to check the status of the PVC. |
| DLCI assigned to wrong subinterface | Step 1 Use the show frame-relay pvc privileged EXEC command to check the assigned DLCIs. Make sure that the correct DLCIs are assigned to the correct subinterface.
Step 2 If the DLCIs appear to be correct, shut down the main interface using the shutdown interface configuration command, then bring the interface back up using the no shutdown command. |
Symptom: Attempts to ping the remote router across a Frame Relay connection fail.
Table 16-2 outlines the problems that might cause this symptom and describes solutions to those problems.
| Possible Problem | Solution |
|---|---|
| Encapsulation mismatch | Step 1 When connecting Cisco devices with non-Cisco devices, you must use IETF encapsulation on both devices. Check the encapsulation type on the Cisco device with the show frame-relay map EXEC command.
Step 2 If the Cisco device is not using IETF encapsulation, use the encapsulation frame-relay ietf interface configuration command to configure IETF encapsulation on the Cisco Frame Relay interface. For information on viewing or changing the configuration of the non-Cisco device, refer to the vendor documentation. |
| DLCI inactive or deleted | Step 1 Use the show frame-relay pvc EXEC command to view the status of the interface's PVC.
Step 2 If the output shows that the PVC is inactive or deleted, there is a problem along the path to the remote router. Check the remote router or contact your carrier to check the status of the PVC. |
| DLCI assigned to wrong subinterface | Step 1 Use the show frame-relay pvc privileged EXEC command to check the assigned DLCIs. Make sure that the correct DLCIs are assigned to the correct subinterfaces.
Step 2 If the DLCIs appear to be correct, shut down the main interface using the shutdown interface configuration command, then bring the interface back up using the no shutdown command. |
| Misconfigured access list | Step 1 Use the show access-list privileged EXEC command to see if there are access lists configured on the router.
Step 2 If there are access lists configured, test connectivity by disabling access lists using the no access-group global configuration command. Check to see if connectivity is restored. Step 3 If connections work, reenable access lists one at a time, checking connections after enabling each access list. Step 4 If enabling an access list blocks connections, make sure that the access list does not deny necessary traffic. Make sure to configure explicit permit statements for any traffic you want to pass. Step 5 Continue testing access lists until all access lists are restored and connections still work. |
| frame-relay map command missing | Step 1 Use the show frame-relay map privileged EXEC command to see if an address map is configured for the DLCI.
Step 2 If you do not see an address map for the DLCI, enter the clear frame-relay-inarp privileged EXEC command and then use the show frame-relay map command again to see if there is now a map to DLCI. Step 3 If there is no map to the DLCI, add a static address map. Use the frame-relay map interface configuration command.1 Step 4 Make sure that the DLCIs and next-hop addresses specified in frame-relay map commands are correct. The specified protocol address should be in the same network as your local Frame Relay interface. For complete information on configuring Frame Relay address maps, refer to the Cisco IOS Wide-Area Networking Configuration Guide publication. |
| No broadcast keyword in frame-relay map statements | Step 1 Use the show running-config privileged EXEC command on local and remote routers to view the router configuration. Check frame-relay map command entries to see if the broadcast keyword is specified.
Step 2 If the keyword is not specified, add the broadcast keyword to all frame-relay map commands. Note: By default, the broadcast keyword is added to dynamic maps learned via Inverse ARP. |
Symptom: Attempts to ping devices on a remote network across a Frame Relay connection fail.
Table 16-3 outlines the problems that might cause this symptom and describes solutions to those problems.
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