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Old 08-13-2007, 09:27 AM   #1
Registered: Jun 2004
Posts: 39

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How to detect Ethernet switch loops


Our lab recently suffered frequent network timeouts/unavailabilities that we traced to two switches that had three connections between them. We currently believe that these less-expensive switches do not support a spanning tree protocol. What tools exist to detect and isolate a problem like this (switch loops)?

Old 08-13-2007, 06:56 PM   #2
Registered: Jun 2007
Posts: 359

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hi tlemons,

are those really old switches?
try to see the LED - and read the manual.
every loop will terminate one of the connection.

if you want to "legitimate" loop then you should disable STP and doing etherchannel/port aggregation protocol or IST interswitch trunk. but you must make sure you have a loop free network.


Last edited by rossonieri#1; 08-13-2007 at 06:58 PM.
Old 08-15-2007, 01:14 PM   #3
Registered: Jun 2004
Posts: 39

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Thanks for the reply. No, these are not old switches, but are cheap Netgear switches that do not include any form of spanning tree protocol. So, when someone connected two switches together using three different cables, network performance was horrible while the network tried to recover from this problem. I want to find a way to detect this is happening.




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