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Basic troubleshooting guide (For circuits using Nortel routers and GDC modems) When power is applied to a router it attempts to contact the upstream Frame Switch by transmitting, every 10 seconds/six per minute, a 'Full Status Request' over the Control PVC [Permanent Virtual Circuit]. At this point a 'show fr pvcs' command on the router will show the control DLCI only [1023 or 0]. When the Frame Switch detects the incoming 'Full Status Request' it responds by returning a 'Full Status Report' to the router. From this report the router learns the DLCI number [ie 800] of the Data PVC and switches to sending five 'Keep Alive' and one 'Full Status Request' every minute. A 'show fr pvcs' command on the router will now show the Control DLCI and an 'Inactive' data DLCI. The Frame Switch will then complete the setup of the circuit to the far end. Once the circuit is completed a 'show fr pvcs' command on the router will finally show the Control DLCI and an 'Active' data DLCI. This simple sequence of events is identical on both ends of the circuit and is conducive to easy troubleshooting.
If the Data DLCI is absent use the 'show fr stats' command over a period of at least 1 minute to compare the incrementation of the Control DLCI's transmitted and received frame and octet counts. If the received octet count increments the same amount as the transmitted octet count the circuit is looped back. If the received and transmitted frame counts are not incrementing the same amount erratic responses are being received from the Frame Switch. In each case we need to verify our equipment by looping back the NID end of the CAT5 cable, then again using the 'show fr stats' command to show the router's transmitted octets being received back as determined by their identical sizes. If they are present we know the router is transmitting the Control DLCI frames but the Frame Switch is not responding. This indicates a misconfigured Frame Switch, a bad CSU/DSU or a bad circuit. If the Control DLCI does not show returning frames or octets there is a bad router, V.35 cable, modem, or CAT5 cable. Note: An Innovyx modem cannot be looped back.
After installing and powering up the modem there should be no alarms, and connecting the router to the modem will cause the modem's 'SD' light to illuminate. If so, go to the 'Completing Installation' section of this procedure. If not, first double check the modem configuration and cable installation, then perform the following tests. 1........Looping back the NID end of the modem's CAT5 cable should clear any alarms and point to a suspect circuit. If the alarms do not clear the modem or CAT5 cable are defective. If the alarms do clear, and if a router is connected to the modem, the 'SD' and 'RD' lights will illuminate to further point to the circuit as the failure. Note:The GDC Innovyx modems cannot be looped back. 2........Setup and install another modem. If the faults reoccur the circuit is suspect. If not, the first modem was defective. 3........Using a crossover cable, connect two modems back-to-back to ensure they show no alarms. If alarms exist, a modem or crossover cable is faulty. If alarms do not exist, the circuit is again suspect. If the alarms do clear, and a router is then connected to the first modem, it's 'SD' light will illuminate, causing the second modem's 'RD' light to illuminate. Next, install a V.35 loopback connector onto the second modem to illuminate it's 'SD' light and cause the first modem's 'RD' light to illuminate. This also points to the circuit as the failure. Note:The GDC Innovyx modems will not operate when connected back-to-back. However, an Innovyx will work fine with the older version modems. 4.........Use a T1 Tester on a T1 to detect any failures. A T1 tester and a V.35 loopback connector can also be used to test a modem. Note: A T1 tester will test only T1 installations, not DDS[56k] installations. ****Modems with 'TM' alarms or ip/management problems can often be repaired by reseating chips on the mother board. ****After a modem is replaced it's MAC address must be changed in the router. This can be accomplished by rebooting the router, or, by entering on the router 'clear ip arp xxx.xxx.xxx.xxx' using the modem's ip address.
After router, modem and hub installation has been completed the modem should have it's 'SD' and 'RD' lights lit. Console into the router and use the 'show ip circuits' command to ensure the Ethernet and Sync ports are up. If the Sync port is down suspect the circuit, CAT5 cable, modem, V.35 cable or router. If the ethernet port is down the hub is disconnected, the CAT5 cable is bad or the router is suspect. Using the 'show fr pvcs' command ensure there is an active Data DLCI. If inactive the router is communicating with the Frame Switch but the PVC has not been completed succesfully, this can be caused by misconfigured equipment at the far end but is usually a problem with the circuit. If the Data DLCI is absent go to the 'Router' section of this procedure. If active, ping an address located at the far end of the circuit. If unsuccessful there is a problem with the WAN or the router's configuration. If successful telnet to a machine on the other end of the circuit and ping back to the local modem and router. If unsuccessful, check the equipment configuration. If successful, the circuit is operational. ****In the absence of a hub a LAN crossover cable can be used to bring up the router's Ethernet port. Connect a laptop configured for the local LAN to the router's ethernet [UTP] port. Optionally, in a T1 installation connect the router's ethernet port to the modem's 10BaseT connector. Also, if a modem seems to not be pingable, again use the crossover cable to connect a laptop to the 10BaseT connector and ping it from there.
1: - Goes to volume 1 on router dir - Displays directory of router s wfTelnetClient.2.0 1;commit - Configures telnet on router enable telnet - Enables telnet on router disable telnet - Disables telnet on router show fr pvcs - Shows Control DLCI, and Data DLCI's as active or inactive show fr stats - Shows DLCI's "sent" and "received" frame/octet and discards/drops show ip cir - Shows "ethernet" and "sync" port's up/down status, ip addresses, masks show ip arp - Shows local host ip/mac addresses clear ip arp ***.***.***.*** - Clears the IP/MAC address from the arp table show ip stats - Shows "ethernet" and "sync" ports ip addresses, in receives, out requests, forwards, in discards and out discards ping ***.***.***.*** -p - Performs a traceroute to the specified address telnet - Starts telnet session on router open ***.***.***.*** - Opens ip in telnet session quit - Quits telnet session ! - Repeats last command ! 50 - Repeats last command 50 times ! 0 - Repeats last command indefinately, Ctrl C stops action. more off - Turns off screen size limits more on - Turns on screen size limits more 50 - Sets screen size to 50 lines get wfHwEntry.26.* - Displays the booted config file get wfSys.*.0 - Shows system info such as name, contact, location and wan tech Ctrl C or Ctrl shift c - Stops actions in progress log - Shows router log clearlog - Clears router log date - Shows date and time on router date mm/dd/yy hh:mm:ss - Sets date and time on router stamp - Shows software release g wfSnmp.1.* - Checks if SNMP is enabled 1=enabled, 2=disabled g wfTftp.1.* - Checks if TFTP is enabled 1=enabled, 2=disabled bconfig config local, bconfig image local - These commands in sequence will configure a router to boot locally g wfFrVCircuitEntry.8.* - View number of received packets with FECN bit set. g wfFrVCircuitEntry.9.* - View number of received packets with the BECN bit set. show sync enable -Shows enabled sync ports show sync disable -Shows disabled sync ports s wfSyncEntry.2.1.1 1;commit -Enables Sync port #1 on AN routers. The third number determines the port number. T1 cable pinout: Transmit pair 1/2 Receive pair 4/5 DDS cable pinout: Transmit pair 1/2 Receive pair 7/8
Category 5 Cable Pinouts T1/ESF Alarm conditions |