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New Member

symptom(s) of an STP loop

What would be the symptom(s) of the STP loop on a Cat-6506 switch? What would I look for in the log?

Thanks.

2 REPLIES
New Member

Re: symptom(s) of an STP loop

Hi,

Good question, but not that easy to answer. Some general things to look for the log is messages with

%PaGP

%SPANTREE

%STP

You could also do some for some spanning-tree info depending on what IOS or CatOS you are using the commands will differ slightly. Here is a link to find out more about STP.

http://www.cisco.com/en/US/tech/tk389/tk621/technologies_configuration_example09186a008009467c.shtml

Regards,

Corey

Green

Re: symptom(s) of an STP loop

There really is no such thing as a "Spanning tree Loop;" The two possibilities that come to mind would be a mismatch (IEEE Spanning Tree on some units, and IBM Spanning Tree on others) or a/some switches / bridges that aren't running Spanning Tree, and there could be a Layer Two loop .... which usually shows up as the activity LEDS going from occasional / random blinking to solid on (as the traffic levels build as the result of the loop).

The time span from random to solid will vary somewhat, depending on the traffic levels, but it's generally pretty quick (seconds, if that long).

As far as the logs, I believe you'd get messages saying that the switch is / is not receiving BPDUs from the neighbor switch at xx.xx.xx.xx.xx.xx (MAC).

FWIW

Scott

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