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This chapter explains how to troubleshoot problems and/or conditions experienced once the Cisco 6100 system is up and operational.
Each subsection details the following information about operation troubleshooting.
The following table lists the operation problems described in this chapter and the section names relative to the problem.
| Problem Description | Section Name |
|---|---|
Experiencing data traffic busy signals | |
Unable to train | "Unable to train" |
Unable to train at maximum rate | |
Cisco 675 dropping train | |
System trained but ViewRunner observing SNR fluctuations | |
Subscriber line cannot pass voice |
Logical pools are indicating busy signals and/or subscribers are not seeing solid WAN LED on the Cisco 675.
Logical pools are not sized properly for the number of connection requests over a given period of time or the subscriber(s) has been administratively locked.
1. Check the logical pool performance statistics to see if the number of blocked connections looks high relative to the number of successful connections.
2. Resize the logical pool by either reducing the number of subscribers or increasing the number of modems. The Logical Pool window in ViewRunner provides subscriber to modem ratios.
3. If connection statistics appear sound, check to see of the subscriber(s) configuration data has been deleted, or if their LIM ports have been locked. If so, incoming connection requests on that LIM port will be denied. This can also be detected by witnessing blinking LIM ports on a LIM faceplate during a connection request. The LIM port will not blink if a Cisco 675 connection request is not in process.
The LIM status LED is blinking green, subscriber cannot get line to train.
Subscriber configuration has been deleted or the subscriber's LIM port has been locked.
1. In ViewRunner, check the subscriber's configuration data in the LIM port configuration window (and subsequently nested windows) to see if the subscriber is fully configured (ATM VPI/VCI address(s) are configured). Note a subscriber cannot be unlocked if upstream/downstream data rates are not provisioned.
2. If the configuration is complete, make sure the subscriber, LIM port, and LIM are all unlocked.
3. Consult the ViewRunner for Windows Provisioning and Operation Manual for more information on provisioning subscriber lines properly.
The LIM status LED is off.
LIM power failure.
1. Re-seat LIM to see if LEDs are on during power up and progress through self test.
2. If LEDs are not on, replace module with a second LIM and repeat the first step.
3. If second LIM powers and self tests properly, first LIM has failed.
4. Return failed LIM to Cisco.
The LIM status LED is solid green indicating that the system has trained, but when it sees a blinking ATU-C, it moves on to another ATU-C.
Line quality is so poor that even the lowest data rates in the constellation cannot be achieved.
1. Force the training to occur at 640K downstream / 91 Kbps upstream in ViewRunner. This will "circumvent" the multi-baud training algorithm.
2. If the line will not train and continues to move to other modems, it is possible something happened to the line quality such that it cannot achieve even the lowest of train rates for its reach/gauge/noise impairment model.
3. If the line trains, reset the data rates to the desired upstream/downstream value and retrain. The line should either train at those rates or Rate Adaptive Digital Subscriber Line (RADSL) to the nearest data rate combination.
4. If the line trains, review ATU-C train statistics to see if some modems are exhibiting a significantly higher number of failed trains than others.
5. If so, swap modems into the problem slots and re-check train statistics periodically.
6. Consult the ViewRunner for Windows Provisioning and Operation Manual for more information on multi-baud training.
A line is unable to train at the maximum or provisioned upstream/downstream combination data rates.
Line reach, gauge (including in-home wiring), and/or quality may not enable this rate combination to be achieved, or the logical pool may contain a faulty ATU-C (if one train session enables the rates to be achieved and another train session does not).
Once the line achieves train, use ViewRunner to observe actual versus provisioned trained rates. If they differ, then probably the line reach and/or quality will not permit training at the higher rates while maintaining a better than or equal to 10-7 bit error rate (BER) with a 6 dB noise margin.
The Cisco 675 is not able to sustain the train once it has been established.
Depending on the elapsed time before the retrain attempt occurs, the probable cause varies. If the 675 drops train within a few seconds, follow the steps in this section. If the 675 trains properly for minutes to hours, consult your ISP. It is likely that the ISP has the Cisco FireRunner set for idle or session time-outs.
1. Perform loop test using standard loop verification techniques to determine line quality.
With Release 1.0.2, a given line (and subscriber modem) should find an appropriate upstream/downstream data rate combination rate at which it can hold train with a 6 dB noise margin, and still enable at least a 10-7 BER.
If this cannot be met on a given modem, the multi-baud train mechanism assumes a failed train. The system controller (SC) increments a failed train counter and moves the subscriber to the next available modem in the logical pool. The ATU-R/C attempt retrain. This process continues indefinitely (in Release 1.0.2).
If the Signal-to-Noise Ratio (SNR) is not reaching 20, the line quality is typically too poor to maintain training with the 10-7 BER protection at 6 dB noise margin.
The system is trained, but the ViewRunner is observing SNR fluctuations.
Could be a faulty ATU-C or ATU-C with an improper module software image (incompatible with the system image).
1. Small fluctuations of 2-3 dB observed by ViewRunner on refresh are acceptable. No action is necessary.
2. Large fluctuations of > 6 dB will cause the line to drop and attempt to retrain on the next round-robin port. These fluctuations do not show up on ViewRunner as the SNR data is lost on the disconnect. No action is required here since the modem should retrain, just at a lower upstream/downstream combination.
3. If a successful train with erratic SNR values (revealed with multiple ViewRunner refreshes on ATU-C status) is observed, check the ATU-Cs software version against release notes for the system image being run in this particular 6100. If they do not match, upgrade the ATU-C.
The system cannot pass voice.
There are many circumstances in which a subscriber line cannot pass voice:
1. Check both the CPE and Central Office (CO) ends to make sure that you have the right filter for the phone type.
2. Check to make sure that the wiring punch downs at the MDF are correct.
3. Check the Tip/Ring pair from the MDF to the 6100 POTS splitter chassis (PSC) and back to the MDF for continuity.
4. Replace CO splitter or CPE splitter.
5. See "Verifying Connectivity on Install" in the "BERT Testing and System Set Up Verification" appendix for instructions on how to check continuity.
Posted: Tue Nov 16 11:47:08 PST 1999
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