Cable diagnostics tests

The TDR (Time-domain reflectometer) cable diagnostic test allows an operator to test Ethernet cables for faults without physically disconnecting from the switch. It helps in troubleshooting connectivity or monitor performance on one or more switch ports.

Cable diagnostic test is categorized as four states. Each of the four twisted pairs is displayed in a standard Ethernet cable:

  1. OK: The twisted pair is intact and operating normally for the full length of the cable.

    If displayed for all four pairs, the cable must operate normally with no connectivity or any performance issues.

  2. Short: There is a short between two wires in the same pair.

    A pair that is shorted (example: blue and white) cannot transmit normally, and may cause impaired connectivity or performance for the cable.

  3. Inter-short: There is short between two or more wires in different pairs.

    If multiple pairs are shorted together (example: brown and green), then there is a significant performance degradation or a total loss of connectivity.

  4. Open: There is a gap in one or more pairs resulting in a loss of continuity, or no cable is connected to the port.

    It may indicate a damaged or cut cable. A port that has no cable connected is display Open for all pairs.

To start a cable diagnostic test, use the following command (in this example, port 1 and 2 are tested):

switch# test cable-diagnostics 1-2

This command will cause a loss of link on all tested ports and will take
several seconds per port to complete.  Use the 'show cable-diagnostics'
command to view the results.

Continue (y/n)?  y
 
After the test is complete, use the following command to view the test results:

switch# show cable-diagnostics 

Cable Diagnostic Status - Copper Ports
 
       MDI    Cable       Cable Length or       
  Port Pair   Status      Distance to Fault     
  ---- ------ ----------- --------------------- 
  1    1-2    OK          2m                    
       3-6    OK          4m                    
       4-5    OK          2m                    
       7-8    OK          2m                    
  2    1-2    Open        0m                    
       3-6    Open        0m                    
       4-5    Open        0m                    
       7-8    Open        0m
NOTE:
  • Running a cable diagnostic test will result in a brief interruption in connectivity on all tested ports.
  • Displayed cable lengths and distances to detected faults are approximate (error margin is ± 10% of cable length).

Syntax

test cable-diagnostics <PORT-LIST>

Description

Use the command to test for cable faults.

Parameter

PORT-LIST

Specify copper port as an input port number.

Test cable-diagnostics C21

test cable-diagnostics C21

The 'test cable-diagnostics' command will cause a loss of link and will take a few seconds per interface to complete.
Continue [Y/N]? y

MDI         Cable    Distance    Pair   Pair        MDI
Port Pair   Status   to Fault    Skew   Polarity    Mode
---------   ------   --------    -----   ------   ------
C21 1-2       Open       0 m      0 ns
    3-6       Open       0 m      0 ns
    4-5       Open       0 m      0 ns
    7-8       Open       1 m      0 ns

Test cable-diagnostics 1/1-1/10

switch# test cable-diagnostics 1/1-1/10

This command will cause a loss of link on all tested ports and will take
several seconds per port to complete.  Use the ‘show cable-diagnostics’ command to view
 the results.

Continue (y/n)? Y

switch# show cable-diagnostics 1/1-1/10

Cable Diagnostic Status - Copper Ports

       MDI    Cable       Cable Length or
  Port Pair   Status      Distance to Fault
  ---- ------ ----------- ---------------------
  1/1  1-2    OK          5m
       3-6    OK          5m
       4-5    OK          7m
       7-8    OK          7m
  1/2  1-2    OK          7m
       3-6    OK          7m
       4-5    OK          7m
       7-8    OK          7m
  1/3  1-2    OK          5m
       3-6    OK          7m
       4-5    OK          5m
       7-8    OK          7m
  1/4  1-2    OK          7m
       3-6    OK          7m
       4-5    OK          7m
       7-8    OK          5m
  1/5  1-2    OK          4m
       3-6    OK          5m
       4-5    OK          5m
       7-8    OK          4m
  1/6  1-2    OK          4m
       3-6    OK          4m
       4-5    OK          4m
       7-8    OK          4m
  1/7  1-2    OK          5m
       3-6    OK          4m
       4-5    OK          5m
       7-8    OK          4m
  1/8  1-2    OK          4m
       3-6    OK          5m
       4-5    OK          4m
       7-8    OK          4m
  1/9  1-2    OK          5m
       3-6    OK          5m
       4-5    OK          5m
       7-8    OK          5m
  1/10 1-2    OK          7m
       3-6    OK          5m
       4-5    OK          5m
       7-8    OK          5m

Good cable tests

switch# test cable-diagnostics 51

This command will cause a loss of link on all tested ports and will take
several seconds per port to complete.  Use the 'show cable-diagnostics'
command to view the results.

Continue (y/n)? Y

switch# show cable-diagnostics 51

Cable Diagnostic Status - Transceiver Ports

         MDI    Cable       Distance   Pair    Pair       MDI
  Port   Pair   Status      to Fault   Skew    Polarity   Mode
  ---- ------   ---------   --------   -----   -------   -----
  51     1-2      OK           0 m      8 ns   Normal     MDI
         3-6      OK           0 m      8 ns   Normal
         4-5      OK           0 m      8 ns   Normal     MDIX
         7-8      OK           0 m      0 ns   Normal


switch# test cable-diagnostics 52

This command will cause a loss of link on all tested ports and will take
several seconds per port to complete.  Use the 'show cable-diagnostics'
command to view the results.

Continue (y/n)?  Y

switch# show cable-diagnostics 52

Cable Diagnostic Status - Transceiver Ports

         MDI    Cable       Distance   Pair    Pair       MDI
  Port   Pair   Status      to Fault   Skew    Polarity   Mode
  ---- ------   ---------   --------   -----   -------   -----
  52    1-2       OK          0 m       0 ns   Normal     MDI
        3-6       OK          0 m       0 ns   Normal
        4-5       OK          0 m       0 ns   Normal     MDIX
        7-8       OK          0 m       0 ns   Normal

Faulty cable test

switch# test cable-diagnostics 51
This command will cause a loss of link on all tested ports and will take
several seconds per port to complete.  Use the 'show cable-diagnostics'
command to view the results.

Continue (y/n)?  y
switch# show cable-diagnostics 51

Cable Diagnostic Status - Transceiver Ports

       MDI    Cable       Distance   Pair   Pair       MDI
  Port Pair   Status      to Fault   Skew   Polarity   Mode
  ---- ------ ----------- ---------- ------ ---------- ------
  51    1-2    OK          0 m        0 ns
        3-6    Short       1 m        0 ns
        4-5    Short       1 m        0 ns
        7-8    OK          0 m        0 ns


switch# test cable-diagnostics 52

This command will cause a loss of link on all tested ports and will take
several seconds per port to complete.  Use the 'show cable-diagnostics'
command to view the results.

Continue (y/n)?  Y

switch# show cable-diagnostics 52

Cable Diagnostic Status - Transceiver Ports

       MDI    Cable       Distance   Pair   Pair       MDI
  Port Pair   Status      to Fault   Skew   Polarity   Mode
  ---- ------ ----------- ---------- ------ ---------- ------
  52   1-2     Open        0 m        0 ns
       3-6     Open        0 m        0 ns
       4-5     Open        1 m        0 ns
       7-8     Open        0 m        0 ns

Error message

Error Message

Cause

The transceiver on port 1/A1 does not support cable diagnostics.

  • usage of invalid(fiber-SFP+) port

  • The selected range includes an entry for an invalid port.