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:
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.
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.
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.
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
- 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. |
|