How many times have been working on a problem and got to the point where you thought it might be the cable that’s causing the issue? I do and since I can’t afford a Fluke, I use the next best thing….IOS! You first run the test and then you can view the results (two separate commands). Here’s a an example of a bad cable run and and good one.

SW#test cable-diagnostics tdr interface gi1/0/3 
Link state may be affected during TDR test
TDR test started on interface Gi1/0/3
A TDR test can take a few seconds to run on an interface
Use 'show cable-diagnostics tdr' to read the TDR results.

SW#show cable-diagnostics tdr int gi1/0/3 
TDR test last run on: December 17 19:49:44

Interface Speed Local pair Pair length Remote pair Pair status
--------- ----- ---------- ------------------ ----------- --------------------
Gi1/0/3 auto Pair A N/A Pair B Normal 
 Pair B N/A Pair A Normal 
 Pair C 1 +/- 2 meters Pair D Short 
 Pair D 1 +/- 2 meters Pair C Short

 

SW#test cable-diagnostics tdr interface gi2/0/24
TDR test started on interface Gi2/0/24
A TDR test can take a few seconds to run on an interface
Use 'show cable-diagnostics tdr' to read the TDR results.

SW#show cable-diagnostics tdr int gi2/0/24 
TDR test last run on: December 17 19:50:17

Interface Speed Local pair Pair length Remote pair Pair status
--------- ----- ---------- ------------------ ----------- --------------------
Gi2/0/24 1000M Pair A 0 +/- 4 meters Pair A Normal 
Pair B 0 +/- 4 meters Pair B Normal 
Pair C 0 +/- 4 meters Pair C Normal 
Pair D 0 +/- 4 meters Pair D Normal