doing a time-domain reflectometer (TDR) test on a cisco Switch can identify problems with a cable and it will show you the length of the cable. “A TDR will transmit a short time pulse along the conductor, If the conductor is of a uniform impedance and is properly terminated, the entire transmitted pulse will be absorbed in the far-end termination and no signal will be reflected toward the TDR. Any impedance discontinuities will cause some of the incident signal to be sent back towards the source”. Wiki
SW01#test cable-diagnostics tdr interface gi2/0/5
TDR test started on interface Gi2/0/5
A TDR test can take a few seconds to run on an interface
Use ‘show cable-diagnostics tdr’ to read the TDR results.
To view test
SW01#show cable-diagnostics tdr in gi2/0/5
TDR test last run on: July 07 09:30:33Interface Speed Local pair Pair length Remote pair Pair status
——— —– ———- —————— ———– ——————–
Gi2/0/5 1000M Pair A 23 +/- 4 meters Pair A Normal
Pair B 23 +/- 4 meters Pair B Normal
Pair C 23 +/- 4 meters Pair C Normal
Pair D 24 +/- 4 meters Pair D Normal
The above gives you information such as, the 1gb link, what pairs tested as “normal” and it was 4 meters in length
