Solved

Perfect crosstalk?

Posted on 2013-01-03
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Last Modified: 2013-01-27
Weekend fun:

(I know it's not best practice, don't tell me... :) )
Setup: only one cat5 (solid core, around 50-60m run) copper to a classroom, need access for lecturer PC and wireless AP. Instead of small managed switch, I went with a passive splitter.
AP receives 24V POE on far end after splitter.
AP immediately falls back to and stays on 10meg connection, error counter on 0 after days, appears to be working perfectly, wireless clients happy.
Fun part: sometimes the MAC of the AP appears on the 'wifi vlan' port (good thing), and also on the 'student vlan' port where the split cable PC is.
Double-checked, vlans are not bridged together in the area.

So: what's your guess? Perfect, full-frame crosstalk on the splitted cable, or the otherwise perfectly reliable 3Com 4400 box started bleeding between vlans, or other?

Cheers,
Tamas
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Question by:TimotiSt
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3 Comments
 
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Assisted Solution

by:Craig Beck
Craig Beck earned 300 total points
ID: 38747443
Crosstalk wouldn't make a MAC address appear on a different port.  This would only be caused by a bridge or loop.

Do any of your student clients have wired and wireless connections back to the same switch?  If so, make sure none of them have inadvertently bridged their NICs.

Also, make sure your STP is working properly.
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TimotiSt earned 0 total points
ID: 38804935
Okay, got this one:
The Cat5 run in the wall is patched up somewhere, where it has strange cable shorts. Pins 1,2,3 and 6 are not shorted to each other, but they are to random other pins, so it's a mess...
Couldn't originally debug with my cheap cable tester...
Anyways, it kinda works with only one 100Meg connection, without a passive splitter. But I'll definitely need a new cable run...

Tamas
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Author Closing Comment

by:TimotiSt
ID: 38823762
Managed to debug the cable.
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