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Cisco AS5800 Series Universal Gateways

Field Notice: Incorrect AS5800 T1 Long Haul Configurations May Cause Line Errors


March 20, 1998



Products Affected

This field notice affects the following product:

  • DS58-12CT1

    DS5800 12 Port T1 Ingress Line Card

Background

Cisco has determined that an incorrectly configured T1 long haul may cause line errors and the T1 controller will not come up. E1 interfaces are not affected.

Long Haul vs. Short Haul Summary

Cable Length Short-Haul:

The following cable length short-haul configurations define the length range (in feet) between your Network Access Server (NAS) and your repeater:

  • 133 feet (0-133 feet)

  • 266 feet (134-266 feet)

  • 399 feet (267-399 feet)

  • 533 feet (400-533 feet)

  • 655 feet (534-655 feet)

Cable Length Long-Haul:

The following cable length long-haul configurations define the length range in gain and pulse between your NAS and your repeater. The cablelength long-haul command is configured for a channelized T1 only and includes the following gain and pulse arguments:

Receive Gain:

  • gain 26 (26db Gain)

  • gain 36 (36db Gain)

Transmit Signal Strength:

  • -15db (-15db pulse)

  • -22.5db (-22.5 db pulse)

  • -7.5db (-7.5 db pulse)

  • 0db (0 db pulse)

Problem Description

If the AS5800 T1 long haul interface receives a -4dB signal or greater, the port may report line errors. This will usually be the case if the far side transmits a 0db signal and there is a relatively short cable length (100s of feet).

Problem Symptoms

Systems with incorrectly configured T1 interfaces will not come up, and the show controller t1 command will indicate that the port is down and report Line Code Violations.

Output of a correctly configured T1 line:

AS5800-1> show controller t1 1/0/1
T1 1/0/1 is up.  
 No alarms detected.  
 Framing is ESF, Line Code is B8ZS, Clock Source is Line.  
 Data in current interval (540 seconds elapsed):  
  0 Line Code Violations, 0 Path Code Violations  
  0 Slip Secs, 0 Fr Loss Secs, 0 Line Err Secs, 0 Degraded Mins  
  0 Errored Secs, 0 Bursty Err Secs, 0 Severely Err Secs, 0 Unavail Secs

Note:?A few errors when the T1 line comes up for the first time, or slowly over time, is acceptable.

Workaround/Solution

The DS58-12CT1 should be configured for short haul mode unless there is at least 5db attenuation on the incoming signal. This attenuation can either come from a length of cable or by setting the remote side to not transmit a 0dB signal.

Configuring Cable Length:

When you configure your channelized T1 trunk cards, you must include the output signal strength. This is done by specifying the distance to the repeater in short haul mode, or setting transmit signal attenuation in dB in long haul mode.

In either case, this is accomplished by using the cablelength command. No cablelength command exists for E1 cards.

Instructions on configuring cable length are available below, as well as in the "Configuring Your Cisco AS5800 Universal Access Server" document here on CCO.

AS5800-1# configure terminal  
Enter configuration commands, one per line. End with CNTL/Z.  
AS5800-1(config)# controller t1 shelf/slot/port
  
AS5800-1(config-controller)# cablelength short {133 | 266 | 399 | 533 | 655}  
           [or]  
AS5800-1(config-controller)# cablelength long {gain 26 | gain 36} {-15 | -22.5 | -7.5 | 0}  
AS5800-1(config-controller)# exit  
           [or]  
AS5800-1(config-controller)# Ctrl-Z  
AS5800-1# copy running-config startup-config  

Verify your controller is operative using the show controller t1 or show controller e1 command:

AS5800-1> show controller t1 1/0/1  
T1 1/0/1 is up.  
  No alarms detected.  
  Framing is ESF, Line Code is B8ZS, Clock Source is Line.  
  Data in current interval (540 seconds elapsed):  
     0 Line Code Violations, 0 Path Code Violations  
     0 Slip Secs, 0 Fr Loss Secs, 0 Line Err Secs, 0 Degraded Mins  
     0 Errored Secs, 0 Bursty Err Secs, 0 Severely Err Secs, 0 Unavail Secs

<test omitted>

Total Data (last 24 hours)  
     0 Line Code Violations, 0 Path Code Violations,  
     0 Slip Secs, 0 Fr Loss Secs, 0 Line Err Secs, 0 Degraded Mins,  
     0 Errored Secs, 0 Bursty Err Secs, 0 Severely Err Secs, 0 Unavail Secs

For More Information

If you require further assistance, or if you have any further questions regarding this field notice, please contact the Cisco Systems Technical Assistance Center (TAC) by one of the following methods: