Channel Group Creation Over Stacked Switches

Unanswered Question
Sep 16th, 2010
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Please everyone bear with me... This is my first post on an Cisco forum and I'm a real newbie to this lark - everyone's got to start somewhere right?!?! :-)

I've got two Cisco 3750 switches stacked together and want to connect some Dell Blades to them.

These Dell blades have got two NICS per blade, so I thought it would be best practice would be to plug one NIC into the top switch and plug the other NIC into the bottom switch.

Then I thought it would be best to create a port channel group for the two ports based on that one blade - I was able to put the top switch into channel-group 1 mode auto but when I run the command on the other port based in the bottom switch I get the following message

%With PAgP enabled, all ports in the Channel should belong to the same switch
Command rejected (Port-channel1, Gi2/0/7): Invalid etherchnl mode

I've not Google'd it yet but thought I'd use this forum...

Is it even possible to group ports together over different switches even though they are stacked or do I have to put both NICS into the same switch and then create the channel-group.



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ashok_boin Thu, 09/16/2010 - 04:20
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Hi Dave,

You can indeed create cross stack etherchannel.

Pls find the following link which has given nice explanation how to create this. The catch here is you need to disable both PAgP and LACP to create cross stack etherchannels.

All the best



jorge.calvo Thu, 09/16/2010 - 04:23
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Hello David,

Welcome to this forum. In regards to your question, try disabling PagP negotiation configuring the Ether-Channel with the command:

channel-group 1 mode on

Or you can also use LACP negotiation with the command:

channel-group 1 mode active

Hope this helps.


glen.grant Thu, 09/16/2010 - 04:30
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Jorge is correct you can also use LACP  to create your channels.  You can't use PAGP to create the channel as pagp is cisco proprietary  and is not allowed for "crosstack"  etherchannel . If you want to create a channel on the same switch to another piece of cisco gear you can use PAGP .


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