Moving from a single 802.1q trunk to etherchannel 802.1q trunk

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Feb 27th, 2012
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I have some servers that are showing signs of using more bandwidth than the single 802.1q trunk connection can feed them (a single 1 Gig connection).  I am going to add a second switch to make a stack (using 3750's) and with that move to an etherchannel 802.1q trunk configuration of 4 1 gig connections.  I have been researching this and if I understand things correctly, with etherchannel trunk 802.1q configurations, the work is done at the port-channel interface and all I have at the physical interface is channel-group 1 mode on ?

What I would like to do is the add the channel-group 1 mode on command to the existing physical trunk interface and then take away the individual trunk commands from the physical interface, will that be doable or just leave the commands on the physical interface since they wont be doing anything ?  Would I then just add the channel-troup 1 mode on command to each additional interface that I want to be a part of the etherchannel config ?

On a related question as the port channel numbering, from what I have read the port channel number is local to the switch it is being configured on.  So based on that, should I use the same port channel number on each end of a particular etherchannel config or does it matter ?


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Jon Marshall Mon, 02/27/2012 - 10:22
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You can leave them on the physical or move them to the logical which is where you configure charactertistics common to all physical interfaces. Bear in mind settings like speed/duplex should be done on the physical interfaces.

You can then, as you say, add "channel-group mode " to each physical interface you want to add to the etherchannel.

The number is indeed local to each switch so it really doesn't matter whether you use the same number or not. Might make it easier to administer if you did though.


Leo Laohoo Mon, 02/27/2012 - 13:25
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I agree with Jon.  You can configure a single dot1Q trunk into etherchannel by simply entering the command "channel-group mode auto".   With the 3750 it's even simpler before you add additional stack member because you can pre-provision your ports.

Note that when you are dealing with etherchannel, things to consider:

1.  All the physical ports should have the same configuration;

2.  If, for example, you need to add/remove VLANs from the etherchannel, add/remove from the PortChannel interface and not at the individual physical interface. 


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