| [Info] Cable testing built in to IOSA colleague showed me this yesterday:
Switch#test cable-diagnostics tdr interface type number
Read the on-screen output, wait a few seconds then run
sho cable-diagnostics tdr int type number
Here's me having a crack at it.
Switch#sho cable-diagnostics tdr int gig 1/0/48
TDR test last run on: January 24 21:55:55
Interface Speed Local pair Pair length Remote pair Pair status
--------- ----- ---------- ------------------ ----------- --------------------
Gi1/0/48 1000M Pair A 28 +/- 0 meters Pair B Normal
Pair B 26 +/- 0 meters Pair A Normal
Pair C 29 +/- 0 meters Pair D Normal
Pair D 28 +/- 0 meters Pair C Normal
Not quire sure why there is such a discrepancy in the length, and this example is a crossover cable worked out by MDIX and is part of an etherchannel group.
This was on a 2960S with 12.55 IOS. I believe the command was introduced somewhere around 12.2.
Anyway, just thought I'd share. It could be handy if you're caught short without a cable tester, or you need to test cables remotely ;)
There are lots of other things to test here:
»www.cisco.com/en/US/docs/ios-xml···dem.html
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Binary is as easy as 01 10 11 |
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| And here I was thinking it could only be done on 6500 switches.
Tried the command on a 3750G for chuckles.... NIIIIIICE!
3750G#sh cable-diagnostics tdr int gi 1/0/23
TDR test last run on: January 25 20:41:18
Interface Speed Local pair Pair length Remote pair Pair status
--------- ----- ---------- ------------------ ----------- --------------------
Gi1/0/23 100M Pair A N/A Pair B Normal
Pair B N/A Pair A Normal
Pair C 2 +/- 2 meters Pair D Short
Pair D 2 +/- 2 meters Pair C Short
Regards |
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cramer
join:2007-04-10
Raleigh, NC
kudos:7 | reply to markysharkey
The readings will not be 100% because an accurate (true) TDR is expensive, if it's even doing a real TDR. Most cheap length tests are just capacitance readings.
But, yes, the pair lengths are actually different, due to different amounts of twist on each pair. |
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| reply to markysharkey
Suffice to say, "good enough for twits that say 'there must be a network / cable issue!,'" but if you want to be sure
pack a good 10K dollar Fluke meter.
Been saving this command for the former situation....
Regards |
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| reply to markysharkey
I pack a Fluke Microscanner when I go to site. But when telnetted in the accuracy of the length measurement is less important than confirming one of the sparky's has drilled through a cable... again...
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Binary is as easy as 01 10 11 |
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