1-7 Semester 8 Internetwork Troubleshooting v1.0 - Lab 8.3.4.2 Copyright 2001, Cisco Systems, Inc. Lab 8.3.4.2: TroubleshootingFrameRelay2FrameRelay Atlas 550 192.168.192.0/24 1/2 2/1 S0/0 S0/0 DLCI 17 DLCI 18 .2 .4 Fa0/0 192.168.200.1/24 Fa0/0 192.168.232.1/24 London Singapore Objective Apply the troubleshooting method to a simple FrameRelay network problem. Scenario A new FrameRelay connection was installed between London and Singapore over the weekend. You have been asked to confirm connectivity and that everything is working. Everything seems to be working fine as you can ping and telnet between the London and Singapore LANs. However, upon issuing show frame-relay pvc and show frame-relay map commands on the Singapore router, you see unexpected results. It is your responsibility to determine if the routers are configured correctly and to make appropriate configuration corrections if not. Adtran Atlas 550 Note If using the Adtran Atlas 550 as your FrameRelay switch, you will see information about DLCIs (such as DLCI 16) that is not shown in sample outputs of this lab. These DLCIs are configured on the Atlas 550, but are not being used for this specific lab. You would not normally see these extra DLCIs, so any information pertaining to them should be disregarded for this lab. Step 1 Cable the lab as shown in the diagram. Load the configuration file called Lab8-3-4-2-LondonBrokenConfig.txt into the London router. Load the file called Lab8-3-4-2- SingaporeBrokenConfig.txt into the Singapore router. 2-7 Semester 8 Internetwork Troubleshooting v1.0 - Lab 8.3.4.2 Copyright 2001, Cisco Systems, Inc. Use ping and/or telnet to check connectivity between the London and Singapore LANs. All ping and telnet attempts from either site to the other should be successful. If not, troubleshoot. Step 2 Issue the show frame-relay pvc command on the Singapore router. Your output should appear similar to the sample output below. (Remember to ignore information about other DLCIs [such as DLCI 16] not shown or referenced below.) Singapore#show frame-relay pvc PVC Statistics for interface Serial0/0 (Frame Relay DTE) Active Inactive Deleted Static Local 1 0 1 0 Switched 0 0 0 0 Unused 0 0 0 0 <output omitted> DLCI = 17, DLCI USAGE = LOCAL, PVC STATUS = DELETED, INTERFACE = Serial0/0 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 out bcast pkts 0 out bcast bytes 0 pvc create time 00:15:51, last time pvc status changed 00:14:53 DLCI = 18, DLCI USAGE = LOCAL, PVC STATUS = ACTIVE, INTERFACE = Serial0/0 input pkts 28 output pkts 34 in bytes 5560 out bytes 6623 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 out bcast pkts 34 out bcast bytes 6623 pvc create time 00:15:54, last time pvc status changed 00:15:54 1. What are the unexpected results you are seeing? (Hint: Reference the highlighted output items and look at the network diagram; there is one PVC only and that is to London.) Note: When the status of the PVC is DELETED, it means the FrameRelay switch is not programmed to handle the associated DLCI—at least from this channel or circuit from this router. The focus of the troubleshooting should be on the local router. 3-7 Semester 8 Internetwork Troubleshooting v1.0 - Lab 8.3.4.2 Copyright 2001, Cisco Systems, Inc. Issue the show frame-relay map command on the Singapore router. Your output should appear similar to the sample output below. (Remember to ignore information about other DLCIs [such as DLCI 16] not shown or referenced below.) Singapore#show frame-relay map Serial0/0 (up): ip 0.0.0.0 dlci 18(0x12,0x420) broadcast, CISCO, status defined, active Serial0/0 (up): ip 0.0.0.0 dlci 16(0x10,0x400) broadcast, CISCO, status defined, inactive Serial0/0 (up): ip 192.168.192.2 dlci 18(0x12,0x420), dynamic, broadcast,, status defined, active 2. Reference the network diagram and DLCI 18 information from the show frame-relay pvc output and briefly explain why the show frame- relay map output does not contain any unusual or unexpected results at this point. The unexpected output from the show frame-relay pvc command does not appear to be affecting connectivity or causing other problems. 3. At this point, there does not appear to be a problem; however, if you find the unexpected output from the show frame-relay pvc results from a misconfiguration, should you make a change even though everything is working fine? Step 3 Look at the output of the show frame-relay map command and note the map to London (192.168.192.2) was dynamically established rather than statically. Singapore#show frame-relay map Serial0/0 (up): ip 0.0.0.0 dlci 18(0x12,0x420) broadcast, CISCO, status defined, active <output omitted> Serial0/0 (up): ip 192.168.192.2 dlci 18(0x12,0x420), dynamic, broadcast,, status defined, active 4-7 Semester 8 Internetwork Troubleshooting v1.0 - Lab 8.3.4.2 Copyright 2001, Cisco Systems, Inc. On the Singapore router, shut down the FrameRelay interface, issue a debug frame-relay packet command, then re-enable the interface and note the highlighted items in the sample output below. Singapore(config)#interface serial 0/0 Singapore(config-if)#shutdown Singapore#debug frame-relay packet FrameRelay packet debugging is on Singapore(config)#interface serial 0/0 Singapore(config-if)#no shutdown 04:53:23: Serial0/0: broadcast search <output omitted> 04:54:14: Serial0/0(i): dlci 18(0x421), pkt type 0x2000, datagramsize 289 04:54:32: Serial0/0(i): dlci 18(0x421), pkt encaps 0x0300 0x8000 0x0000 0x806 (ARP), datagramsize 30 04:54:32: Serial0/0: framerelay INARP received 04:54:32: FR: Sending INARP Reply on interface Serial0/0 dlci 18 for link 7(IP) 04:54:37: Serial0/0: broadcast search 04:54:37: Serial0/0: Broadcast on DLCI 16 link 7 04:54:37: DLCI 16 is either deleted or inactive 04:54:37: Serial0/0: Broadcast on DLCI 18 link 7 04:54:37: Serial0/0(o): dlci 18(0x421), pkt type 0x800(IP), datagramsize 64 04:54:37: Serial0/0(o): dlci 18(0x421), pkt type 0x800(IP), datagramsize 64 04:54:37: broadcast dequeue 04:54:37: Serial0/0(o):Pkt sent on dlci 18(0x421), pkt type 0x800(IP), datagramsize 64 <output omitted> Turn debug frame-relay packet off. Singapore#no debug frame-relay packet or no debug all 4. Based upon the map being dynamically established and output from the debug frame-relay packet command, can you determine whether a frame-relay map or frame-relay interface-dlci command was used in the router configuration? (Hint: Inverse ARP.) Since you have determined a frame-relay interface-dlci command was used, you should check the statement with a show running-config command. Your output should appear the same as the partial sample output below. Singapore#show running-config <output omitted> ! interface Serial0/0 ip address 192.168.192.4 255.255.255.0 no ip directed-broadcast encapsulation frame-relay no ip mroute-cache 5-7 Semester 8 Internetwork Troubleshooting v1.0 - Lab 8.3.4.2 Copyright 2001, Cisco Systems, Inc. cdp enable frame-relay interface-dlci 17 frame-relay lmi-type ansi ! <output omitted> 5. What facts can be gathered about the situation? Step 4 6. Examine the facts you have just gathered. Based on your observations, what are the possible causes of DLCI 17 being deleted and DLCI 18 being the active link with London? You call the FrameRelay service provider and they tell you the correct DLCI for the PVC to London is 18. This confirms your findings about why DLCI 17 is deleted while DLCI 18 is active. What happened was the LMI process noticed the DLCI was miconfigured on the Singapore router (frame-relay interface-dlci 17 instead of frame-relay interface-dlci 18). Early in the LMI process, the FrameRelay switch sends the router all of the DLCIs configured for that circuit and for which there should be a PVC to a destination network. In the case of the Singapore router, the FrameRelay switch sent router DLCI 18, the DLCI for the PVC to London. When the Singapore router received this DLCI 18, it did an inverse ARP to map London’s remote IP address to this DLCI since there was no static mapping for DLCI 18 in the Singapore configuration. The Singapore router then deleted DLCI 17 and made DLCI 18 active as you saw in the output of the show frame-relay pvc command. And the output of the show frame-relay map command showed DLCI 18 was mapped to London’s IP address as a result of inverse ARP. If the Singapore router had an incorrect frame-relay map statement instead of a frame-relay interface-dlci statement, the self-correcting automatic inverse ARP process would not have taken place and the connection between Singapore and London would have been down (as was the case in 6-7 Semester 8 Internetwork Troubleshooting v1.0 - Lab 8.3.4.2 Copyright 2001, Cisco Systems, Inc. Lab 8-1). Remember that inverse ARP is automatically disabled for an interface that has a frame-relay map statement configured. Step 5 You have now confirmed everything is working fine and inverse ARP automatically overcame a misconfiguration on the Singapore router. And, as addressed earlier, even though there isn’t a problem, you decide to correct Singapore’s configuration to avoid unforeseen problems later and to help make troubleshooting less difficult. Your action plan is to replace the incorrect frame-relay interface-dlci statement with a corrected one. Step 6 Implement the action plan and observe the results. Remove the existing incorrect frame-relay interface-dlci 17 statement. Enter the correct frame-relay interface-dlci 18 statement. Shutdown then re-enable the interface. Issue a show frame-relay pvc command on the Singapore router. Your output should appear similar to the sample output below. (Remember to ignore information about other DLCIs/DLCI 16.) Singapore#show frame-relay pvc PVC Statistics for interface Serial0/0 (Frame Relay DTE) Active Inactive Deleted Static Local 1 1 0 0 Switched 0 0 0 0 Unused 0 0 0 0 <output omitted> DLCI = 18, DLCI USAGE = LOCAL, PVC STATUS = ACTIVE, INTERFACE = Serial0/0 input pkts 389 output pkts 448 in bytes 77299 out bytes 81761 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 out bcast pkts 448 out bcast bytes 81761 pvc create time 03:46:18, last time pvc status changed 00:00:13 You should now have only one active PVC DLCI 18. Issue a show frame-relay map command on the Singapore router. Your output should appear similar to the sample output below. 7-7 Semester 8 Internetwork Troubleshooting v1.0 - Lab 8.3.4.2 Copyright 2001, Cisco Systems, Inc. Singapore#show frame-relay map Serial0/0 (up): ip 0.0.0.0 dlci 18(0x12,0x420) broadcast, CISCO, status defined, active Serial0/0 (up): ip 0.0.0.0 dlci 16(0x10,0x400) broadcast, CISCO, status defined, inactive Serial0/0 (up): ip 192.168.192.2 dlci 18(0x12,0x420), dynamic, broadcast,, status defined, active Although this output is the same as before, you determined there was an incorrect DLCI number in the Singapore router configuration. This time it is because of the frame-relay interface-dlci 18 statement and not inverse ARP. If you enable debug frame-relay packet and observe the output, you will not see inverse ARP taking place. Use ping and/or telnet to check connectivity between the London and Singapore LANs. All ping and/or telnet attempts from either site to the other should still be successful. 7. Did your solution fix the “problem”? If not, undo your changes and repeat the process. Step 7 8. Document the results. . Internetwork Troubleshooting v1.0 - Lab 8.3.4 .2 Copyright 20 01, Cisco Systems, Inc. Lab 8.3.4 .2: Troubleshooting Frame Relay 2 Frame Relay Atlas 550 1 92. 168.1 92. 0 /24 . 1 92. 168.1 92. 0 /24 1 /2 2/1 S0/0 S0/0 DLCI 17 DLCI 18 .2 .4 Fa0/0 1 92. 168 .20 0.1 /24 Fa0/0 1 92. 168 .23 2.1 /24 London Singapore Objective Apply the troubleshooting