Cisco WAN Switching Modules

Document ID: 10870

Contents

Introduction
Prerequisites
      Requirements
      Components Used
      Conventions
Error Definition
Error Example
Troubleshooting
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Related Information

Introduction

This document discusses broadband trunk module (BTM) Tx CC Pkt Drp errors and provides steps to troubleshoot these errors.

Prerequisites

Requirements

There are no specific requirements for this document.

Components Used

The information in this document applies to the Cisco IGX™ BTM with E1, E2, E3, and T3 backcards.

Conventions

For more information on document conventions, refer to the Cisco Technical Tips Conventions.

Error Definition

BTM packet drop errors indicate the number of cells that are discarded from these trunk queues:

Tx CC Pkt Drp can have these causes:

• The High Priority queue that carries CC packets can overflow during periods of unusually high internodal traffic. The internodal protocol is robust enough to recover from the loss of a small number of CC messages. Sustained periods of Tx CC Pkt Drp errors can cause Comm Fails between nodes, which can lead to Comm Break and unreachable nodes.

  Tx CC Pkt Drp errors rarely occur in networks with T1 trunks or greater bandwidth. When accompanied by Comm Fail and Comm Break messages in dsplog output, then Cisco Technical Support must troubleshoot Tx CC Pkt Drp errors.

• Incorrectly configured trunk parameters, as indicated in the SuperUser-level cnftrkparm command.

Error Example

The likely location of equipment errors is highlighted in yellow in this diagram:

• NT—Network Termination

• MUX—The Multiplexer in the Telco line path.

• Rx—Receive

• Tx—Transmit

Troubleshooting

Follow these steps to troubleshoot the Tx CC Pkt Drp errors.

1. Determine if there is more than one trunk that is experiencing CC Pkt Drps, between the IGX and the rest of the network.

   1. Issue the dsptrks command, to verify the number of routing trunks at the local IGX.

   2. If more than one trunk to the network exists, issue the SuperUser-level drtop command, to identify the trunk that CC traffic uses at the local IGX. The Via Trk column of the drtop output indicates the trunks that are used for CC traffic at the local IGX.

   3. Issue the dspnds command, to determine if there are unreachable nodes on the network.

   4. Issue the cnftrk command and set Restrict PCC traffic to Yes, to route CC traffic off of the trunk that is experiencing CC Pkt Drps.

2. Verify that all trunk parameters are correctly configured.

   1. Compare the configuration of the problem trunk to the default values or to the configuration of other trunks of the same type that work properly.

   2. Issue the cnftrkparm command, to verify the settings of the HighPri queue.

   3. If there is a difference between the configuration of the trunk that is experiencing CC Pkt Drps and the configuration of a working trunk at the same IGX, then contact Cisco Technical Support for further assistance.

3. Issue the SuperUser-level cnfnodeparm command, to check all nodal parameters.

   1. Compare the settings of the IGX that is experiencing the CC Pkt Drps to the settings of an error-free IGX.

   2. If a configuration difference is noted between the IGX that is experiencing CC Pkt Drps and the error-free IGX, contact Cisco Technical Support for further assistance.

If the problem persists after you perform the troubleshooting steps, contact Cisco Systems Technical Support:

• Phone: (800) 553-24HR or (408) 526-7209

• Website: Technical Support - Cisco Systems

• E-mail: tac@cisco.com

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Related Information

• IGX 8400 BTM Trunk Error Troubleshooting and Definitions
• WAN Switching Network Synchronization Fundamentals
• International Telephony Union (ITU) Recommendation G.704
• Cisco WAN Switching Solutions - Cisco Documentation
• Guide to New Names and Colors for WAN Switching Products
• Software Center - WAN Switching Software
• Technical Support - Cisco Systems