dslreports logo
 
    All Forums Hot Topics Gallery
spc

spacer

Search Topic:
uniqs
1771
share rss forum feed

markysharkey
Premium
join:2012-12-20
united kingd
kudos:1

[Info] Cable testing built in to IOS

A colleague showed me this yesterday:

Read the on-screen output, wait a few seconds then run


Here's me having a crack at it.

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:
http://www.cisco.com/en/US/docs/ios-xml/ios/fundamentals/command/test_cable-diagnostics_through_xmodem.html

--
Binary is as easy as 01 10 11

HELLFIRE
Premium
join:2009-11-25
kudos:20
And here I was thinking it could only be done on 6500 switches.

Tried the command on a 3750G for chuckles.... NIIIIIICE!


Regards

cramer
Premium
join:2007-04-10
Raleigh, NC
kudos:9
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.

HELLFIRE
Premium
join:2009-11-25
kudos:20
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

markysharkey
Premium
join:2012-12-20
united kingd
kudos:1
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...
--
Binary is as easy as 01 10 11