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New Member

Stack port flapping


we have just discovered some error messages indicating stack port flapping.

we have swapped stack cable, but error messages wouldn't stop.

It is a 2 x 3750 cisco switches stack, and it has been up and running for quite a while. The redundant stack port is also working fine.

error messages look like this:

Jul 10 16:07:48.903: %STACKMGR-6-STACK_LINK_CHANGE: Stack Port 1 Switch 1 has ch

anged to state UP

Jul 10 16:07:50.455: %STACKMGR-6-STACK_LINK_CHANGE: Stack Port 2 Switch 2 has ch

anged to state UP

Jul 10 16:07:51.462: %STACKMGR-6-STACK_LINK_CHANGE: Stack Port 2 Switch 2 has ch

anged to state DOWN

Jul 10 16:07:51.923: %STACKMGR-6-STACK_LINK_CHANGE: Stack Port 1 Switch 1 has ch

anged to state DOWN

Jul 10 16:07:52.469: %STACKMGR-6-STACK_LINK_CHANGE: Stack Port 2 Switch 2 has ch

anged to state UP

I searched on cisco website but didn't seem to find any solutions to it.

Any input would be much appreciated.



Cisco Employee

Re: Stack port flapping

The error message means that one of the stack connections is flapping,going up-down constantly.

According with the messages, the connection we are having problems with is the one between switch 1 stacking port 1 and switch 2 stacking port 2. This error message could be caused by a faulty stacking cable or a faulty stacking oort. If possible, I would like you to remove the stacking cable connected on these ports and then clear the log and verify if the message stops. Then, if you had a spare stacking cable,it would be a good idea to try it out.

If you do not have a spare cable, in order to determine if the problem is with the cable or the a stacking port it self, we would need to swap the stacking cables around, and if the error message now points to the other two ports, it would be definitively a problem with the stacking port itself.

HTH,Please rate if it does.

-amit singh

New Member

Re: Stack port flapping

Hi Amit,

Thanks for the reply.

- I have swapped a brand new cable, error persists.

- Did what u suggested... removed the cable and error did stop... however, isn't this expected because nothing was plugged into the port hence it wouldn't bother checking?


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