Category:Cisco Systems -> Routing and Switching
Time-domain reflectometer (TDR) is a feature to diagnose and resolve cabling problems. When running TDR, a local device sends a signal through a cable and compares the reflected signal to the initial signal. Layer 1 troubleshooting.
test cable-diagnostics tdr interface gi1/0/42
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show cable-diagnostics tdr interface gi1/0/42
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Remote pair connected:
Remote pair disconnected:
There is also a great article on Cisco website by Leo Laohoo who gives the insight to TDR.
Download link: File:TDR_by_Leo_Laohoo.pdf
More tests:
No patchcord:
Interface Speed Local pair Pair length Remote pair Pair status
--------- ----- ---------- ------------------ ----------- --------------------
Gi3/0/47 auto Pair A 0 +/- 10 meters N/A Open
Pair B 0 +/- 10 meters N/A Open
Pair C 0 +/- 10 meters N/A Open
Pair D 0 +/- 10 meters N/A Open
Patch-cord connected to host directly but host’s network interface is administratively down:
Interface Speed Local pair Pair length Remote pair Pair status
--------- ----- ---------- ------------------ ----------- --------------------
Gi3/0/48 auto Pair A N/A N/A Normal
Pair B 2 +/- 10 meters N/A Open
Pair C 2 +/- 10 meters N/A Open
Pair D 2 +/- 10 meters N/A Short
Patch-cord physically disconnected from the host (no patch-panels):
Interface Speed Local pair Pair length Remote pair Pair status
--------- ----- ---------- ------------------ ----------- --------------------
Gi3/0/48 auto Pair A 1 +/- 10 meters N/A Open
Pair B 1 +/- 10 meters N/A Open
Pair C 1 +/- 10 meters N/A Open
Pair D 2 +/- 10 meters N/A Open
