Physical cable test on a Cisco switch

Here’s how to run a TDR (Time Domain Reflection) cable test on a Cisco Catalyst switch.

This should work on the 2960, 3750 and 4500 range as far as I’m aware.

To run the test :

switch# test cable-diagnostics tdr interface gig 1/0/1
 TDR test started on interface Gi1/0/1
 A TDR test can take a few seconds to run on an interface
 Use 'show cable-diagnostics tdr' to read the TDR results.

Results from a normal cable run look like this :

switch# show cable-diagnostics tdr int gig 1/0/2
Interface Speed Local pair Pair length Remote pair Pair status
--------- ----- ---------- ------------------ ----------- --------------------
Gi1/0/2  1000M Pair A 64 +/- 10 meters Pair B Normal
               Pair B 64 +/- 10 meters Pair A Normal
               Pair C 64 +/- 10 meters Pair D Normal
               Pair D 64 +/- 10 meters Pair C Normal

And from a faulty cable run something like this :

switch# show cable-diagnostics tdr int gig 1/0/1
 Interface Speed Local pair Pair length Remote pair Pair status
 --------- ----- ---------- ------------------ ----------- --------------------
 Gi1/0/1 auto Pair A 0 +/- 10 meters N/A Open
              Pair B 0 +/- 10 meters N/A Short/Crosstalk
              Pair C 1 +/- 10 meters N/A Short/Crosstalk
              Pair D 63 +/- 10 meters N/A Open

Read more here : https://supportforums.cisco.com/blog/9913546/switch-how-test-cable-status