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.

https://supportforums.cisco.com/document/74231/how-use-time-domain-reflectometer-tdr