Interface and Hardware Component Command Reference, Cisco IOS XE Release 3SE (Catalyst 3850 Switches)
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service-module t1 linecode through show controllers satellite

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show cable-diagnostics tdr

To display the test results for the Time Domain Reflectometry (TDR) cable diagnostics, use the showcable-diagnosticstdrcommand in privileged EXEC mode.

show cable-diagnostics tdr interface interface interface-number

Syntax Description

interface interface

Specifies the interface type; valid values arefastethernet and gigabitethernet.


Module and port number.

Command Default

This command has no default settings.

Command Modes

Privileged EXEC

Command History




Support for this command was introduced on the Supervisor Engine 720.


Support for this command on the Supervisor Engine 2 was extended to Release 12.2(17d)SXB.


The output was changed as follows:

  • The Local Pair field was changed to the Pair field. The local pair designations were changed as follows:
    • Pair A to Pair 1-2
    • Pair B to Pair 3-4
    • Pair C to Pair 5-6
    • Pair D to Pair 7-8
  • The Remote Pair field was removed.
  • The Channel field was added to display the pair designation and are as follows:
    • Pair A
    • Pair B
    • Pair C
    • Pair D


This command was integrated into Cisco IOS Release 12.2(33)SRA.

Usage Guidelines

The showcable-diagnosticstdr command is supported on specific modules. See the Release Notes for Cisco IOS Release 12.2 SX on the Catalyst 6500 and Cisco 7600 Supervisor Engine 720, Superivsor Engine 32, and Supervisor Engine 2 for the list of the modules that support TDR.

In the event of an open or shorted cable, the accuracy of length of where the cable is open or shorted is plus or minus 2 meters.

The pair length can be displayed in meters (m), centimeters (cm), or kilometers (km).

If the TDR test has not been run on the port, the following message is displayed:

TDR test was never run on Gi2/12


This example shows how to display the information about the TDR test:

Router# show cable-diagnostics tdr interface gigabitethernet 8/1
TDR test last run on: February 25 11:18:31
Interface Speed Pair Cable length        Distance to fault   Channel Pair status
--------- ----- ---- ------------------- ------------------- ------- ------------
Gi8/1     1000  1-2  1    +/- 6  m       N/A                 Pair B  Terminated  
                3-4  1    +/- 6  m       N/A                 Pair A  Terminated  
                5-6  1    +/- 6  m       N/A                 Pair C  Terminated  
                7-8  1    +/- 6  m       N/A                 Pair D  Terminated 

The table below describes the fields in the showcable-diagnosticstdrcommand output.

Table 1 show cable-diagnostics tdr Command Output Fields




Interface tested.


Current line speed.


Local pair name.

Cable Length

Cable length and accuracy. The accuracy unit is displayed in meters (m), centimeters (cm), or kilometers (km).


Pair designation.

Pair status

Pair status displayed is one of the following:

  • Terminated--The link is up.
  • Shorted--A short is detected on the cable.
  • Open--An opening is detected on the cable.
  • Not Completed--The test on the port failed.
  • Not Supported--The test on the port is not supported.
  • Broken--The pair is bad--either open or shorted.
  • ImpedanceMis--The impedance is mismatched.
  • InProgress--The diagnostic test is in progress.

Related Commands



clear cable-diagnostics tdr

Clears a specific interface or clear all interfaces that support TDR.

test cable-diagnostics

Tests the condition of 10-Gigabit Ethernet links or copper cables on 48-port 10/100/1000 BASE-T modules.