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Asymmetric Digital Subscriber Line (ADSL)

Troubleshooting Layer 1 on a Cisco 1700/2600/3600 ADSL WIC

Document ID: 12960

Updated: Jun 10, 2005

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Introduction

The Cisco 1700, 2600, and 3600 series routers support the asymmetric digital subscriber line (ADSL) WAN interface card (WIC). All three platforms are configured in the same way. However, there are differences in hardware and in the Cisco IOS® Software release required for each one. Throughout this document the Cisco 1700/2600/3600 is called the "Cisco ADSL WIC."

This document describes a procedure to troubleshoot Layer 1 (physical layer) issues on the Cisco ADSL WIC. It includes ADSL cable pinout and status LED descriptions.

The physical layer defines the electrical, mechanical, procedural, and functional specifications to activate , maintain , and de-activate the physical link between communicating network systems. Physical layer specifications define characteristics such as voltage levels, timing of voltage changes, physical data rates, maximum transmission distances, and physical connectors.

Prerequisites

Requirements

There are no specific requirements for this document.

Components Used

This document is not restricted to specific software and hardware versions.

Conventions

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

Check the Cable Pinouts

To troubleshoot Cisco ADSL WIC Layer 1 issues, check the cable pinouts.

  1. Make sure that the cabling is correct and that the Cisco ADSL WIC front panel LEDs function properly.

    The Cisco ADSL WIC has an RJ-11 connector for the ADSL interface. It uses pins 3 and 4 to transfer data.

    Note: For more information on cabling, interface pinouts, and status LED descriptions, refer to the DSL Modem/Router Interface Pinouts and Status LED Descriptions.

    If the interface status shows down, the router does not see a carrier on the ADSL interface. This means that the pins used for the cable are wrong or that your ISP has not turned on DSL service for you. From the router prompt, issue the show interface atm <interface number> command.

    Router#show interface atm 0
    ATM0 is down, line protocol is down
     <... snipped ...>
  2. Make sure that the ADSL Interface (ATM0) is not shut down and that the RJ-11 cable from the ADSL interface of the router is securely plugged in to the wall jack.

    If the interface status shows administratively down, in interface configuration mode under interface ATM 0, issue a no shutdown command.

    Router#show interface atm 0
    ATM0 is administratively down, line protocol is down
     <... snipped ...> 
    
    !--- This shows that the ATM interface is administratively down
    !--- and needs to be turned on.
    
    Router#configure terminal
    Enter configuration commands, one per line.  End with CNTL/Z.
    Router(config)#interface atm 0
    Router(config-if)#no shut
    Router(config-if)#exit
    Router(config)#exit
    Router#
    
    !---  The no shut command turns on the ATM interface.
    
    
  3. In order to view the status or results of a line test and to get information on port status, alarms, configured and actual transmission rates, and transmission errors, use the show dsl interface atm command in EXEC mode.

Troubleshoot the ADSL Interface Modem State

Make sure that you have the right cable pinout and that your ISP has turned on the DSL service. Troubleshoot the DSL connection by watching the modem state of the ADSL interface as the line retrains.

To troubleshoot the modem state, follow these steps:

  1. On the router, issue the terminal monitor and debug atm event commands.

    Router#terminal monitor
    Router#debug atm event
    ATM events debugging is on
    
    !--- These commands enable you to see modem state messages on the screen.
    
    
  2. Physically unplug the ADSL Cable (RJ-11) from the Cisco ADSL WIC ADSL interface. Wait for a few seconds. Plug the cable back in to cause the ADSL line to retrain. If you have access to the digital subscriber line access multiplexer (DSLAM), make the line retrain by shutting down the specific ADSL Terminating Unit - Central Office (ATU-C) interface where the subscriber terminates the DSL connection.

    Note: If you issue the shut and no shut commands on the router, they do not retrain the ADSL line. Even when you administratively shut down the Asynchronous Transfer Mode (ATM) interface, the Carrier Detect (CD) light and the ATU-C port LED are still on. This means that it is still trained up. Unplug and plug back in the ADSL line to make the interface retrain.

  3. Watch the debug messages on the screen.

    If the modem state stays at "0x8" and says "Could not establish connection," it means that the Cisco ADSL WIC has not heard from the central office (CO). It does not see an incoming signal.

    Router# 
    1d01h: DSL: 1: Modem state = 0x8
    1d01h: DSL: 2: Modem state = 0x8
    1d01h: DSL: 3: Modem state = 0x8
    1d01h: DSL: 4: Modem state = 0x8
    1d01h: DSL: 5: Modem state = 0x8
    1d01h: DSL: Could not establish connection
    <... snipped ...> 

    If the modem state changes from "0x8" to "SHOWTIME," it means that the Cisco ADSL WIC has successfully trained with the DSLAM.

    Router#
    00:24:18: DSL: 2: Modem state = 0x8
    00:24:21: DSL: 3: Modem state = 0x8
    00:24:23: DSL: 4: Modem state = 0x8
    00:24:26: DSL: 5: Modem state = 0x8
    00:24:28: DSL: 6: Modem state = 0x10
    00:24:31: DSL: 7: Modem state = 0x10
    00:24:33: DSL: 8: Modem state = 0x10
    00:24:36: DSL: 9: Modem state = 0x10
    00:24:37: DSL: Received response: 0x24
    00:24:37: DSL: Showtime!
    <... snipped ...>
  4. After viewing the debugs, if you do not want to see any more modem state messages, at the router prompt issue the undebug all command. All debugging is turned off.

    Router#undebug all
    

Related Information

Updated: Jun 10, 2005
Document ID: 12960