Many Cisco Switches (3750, 2960x) support some basic cable tests that can be run from the CLI.
To start the tests you run
Switch# test cable-diagnostics tdr interface g0/1 TDR test started on interface Gi0/1 A TDR test can take a few seconds to run on an interface Use ‘show cable-diagnostics tdr’ to read the TDR results.
Then to see the results for a non connected port.
Switch# sh cable-diagnostics tdr int g0/1 TDR test last run on: March 01 00:09:06 Interface Speed Local pair Pair length Remote pair Pair status ——— —– ———- —————— ———– ——————– Gi0/1 auto Pair A 20 +/- 4 meters N/A Open Pair B 20 +/- 4 meters N/A Open Pair C 21 +/- 4 meters N/A Open Pair D 20 +/- 4 meters N/A Open
And this would be a normal result for a port connected to a workstation.
Switch#show cable-diagnostics tdr interface gigabitEthernet 1/0/1#show cable-diagnostics tdr interface gigabitEthernet 1/0/1 TDR test last run on: July 01 07:15:12 Interface Speed Local pair Pair length Remote pair Pair status ——— —– ———- —————— ———– ——————– Gi1/0/1 1000M Pair A 0 +/- 10 meters Pair A Normal Pair B 0 +/- 10 meters Pair B Normal Pair C 0 +/- 10 meters Pair C Normal Pair D 0 +/- 10 meters Pair D Normal
This will generally only work on Copper ports.
Waning this will take down the port you are testing for ~ 10-15 seconds and 45-60 seconds on 6500 and 4500 switches.
This is certainty not a definitive test but is a great tool for looking for broken pairs and remotely troubleshooting issues.
If you want to read up more take a look at this article.