Time-domain
reflectometer, or TDR – is
used to test cables to find faults and it’s a built in cable diagnostic tool.
Active Interface:
SWITCH#test cable-diagnostics tdr interface g1/0/24
TDR test started on interface Gi1/0/24
A TDR test can take a few seconds to run on an interface
Use 'show cable-diagnostics tdr' to read the TDR results.
SWITCH#show cable-diagnostics tdr interface gigabitEthernet 1/0/24
TDR test last run on: February 20 21:26:00
Interface Speed Local pair Pair length Remote pair Pair status
--------- ----- ---------- ------------------ ----------- --------------------
Gi1/0/24 1000M Pair A 20 +/- 4 meters Pair A Normal
Pair B 20 +/- 4 meters Pair B Normal
Pair C 20 +/- 4 meters Pair C Normal
Pair D 18 +/- 4 meters Pair D Normal
INACTIVE INTERFACE:
SWITCH#test cable-diagnostics tdr interface g1/0/23
TDR test started on interface Gi1/0/23
A TDR test can take a few seconds to run on an interface
Use 'show cable-diagnostics tdr' to read the TDR results.
SWITCH#show cable-diagnostics tdr interface gigabitEthernet 1/0/23
TDR test last run on: February 20 21:26:50
Interface Speed Local pair Pair length Remote pair Pair status
--------- ----- ---------- ------------------ ----------- --------------------
Gi1/0/23 auto Pair A N/A N/A Not Completed
Pair B N/A N/A Not Completed
Pair C N/A N/A Not Completed
Pair D N/A N/A Not Completed
SWITCH#
Interface – The interface tested
Speed – Speed of the interface.
Local pair – Pairs detected on the cable connected to the
switch.
Pair length – Approximate length of the cable.
Remote pair – Pairs identified on the far end of the cable.
Pair status – Whether cable is terminated to the far end
device.
Under “Pair status” you can get the following results:
Result
|
Explaination
|
Normal
|
Ideal result you want.
|
Open
|
Open circuit. This means that one (or more) pair has “no pin contact”.
|
Short
|
Short circuit.
|
Impedance Mismatched
|
Bad cable. For more explanation, go here.
|
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