problem with a channel

Unanswered Question
Nov 4th, 2009

I've a problem.

I've connected my VSS Core , with a stack of 6 switch 3750.

If i remove a port that is in channel in the VSS Core and i insert the fiber in another port for error , the port remain down and this is correctly.

If i change the port in the stack of 3750 , the fiber link go up with a problem and all the network have a problem.

There is a feature that i can apply on the stack 3750 , that prevent the gigaport to became UP , if the other link is configured in a channel mode ?

thanks for your help

I have this problem too.
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Giuseppe Larosa Fri, 11/06/2009 - 01:13

Hello Francesco,

I think you should use LACP managed etherchannels so that if no LACP messages are received from the other end when the fiber is moved the port is removed from bundle.

channel-group x mode active

if you are already using it forgive me for this suggestion.

For us it worked

Hope to help


fcostalunga Fri, 11/06/2009 - 01:19

have you an example of configuration or a link that explain this feature ?



fcostalunga Fri, 11/06/2009 - 02:09

i ve read the explain of LACP featura but is not necessary.

I want to prevent a gigaport to became up if in the other end is configured a eterchannel port

Giuseppe Larosa Fri, 11/06/2009 - 02:53

Hello Francesco,

let's see this from another point of view:

the target is that the unwanted link between one standalone port and one port in a bundle has to be teared down.

I'm suggesting that it can be the port configured for LACP etherchannel that can detect the mismatch and can put itself in a suspended status because it is missing the LACP messages from the other side.

I've seen this with servers with multiple NICs and it works.

the port in LACP suspended state does not provide link to other side that is what you are looking for.

the standalone port as far as I know doesn't complain of receiving unexpected LACP messages from other side of the link.

Hope to help



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