Etherchannel with ports on two different switches

Unanswered Question
Aug 6th, 2008

I was wndering if I can have group ports to a etherchannel situtaed on a two different switches (one on Cisco 4506 and another on the Cisco 3750G). At the remote end we have two Cisco 4948 switches, hope that too supports this kind of configuration.

Arabinda

I have this problem too.
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Joseph W. Doherty Wed, 08/06/2008 - 03:01

I believe Etherchannel is only supported on separate physical devices that function as one logical devices. These would include the 3750 or 3750-E in a stack configuration or two 6500s running VSS. (You can also often have Etherchannel across multiple line cards on the chassis switches.)

Don't recall what devices support it, but Multichassis Multilink PPP (MMP) provides a method to define a virtual link across separate physical devices.

rais Wed, 08/06/2008 - 07:30

This should be doable or about to be supported by Cisco switches. Etherchannel from one device to two different switches.

Thanks.

Giuseppe Larosa Wed, 08/06/2008 - 08:43

Hello Arabinda,

this would be quite a deviation from the reason for etherchannel has been introduced:

etherchannel provides a bundle of links that is seen as a single link by STP.

So you can manage to have the links up by not using PAGP or LACP but at STP layer you will go into a trouble because on one side the switch expects to be connected to the same device but on the other sides there are two different devices and STP BDUS will be different.

Keep the two uplinks as separated links and play with per vlan STP cost to have some load-balancing over the two links.

Hope to help

Giuseppe

arabinda.sukla Wed, 08/06/2008 - 22:16

Hi Rais,

The link suggests the kind of etherchannel I want is supported by Cisco 3750G since it has the facility of stacking. unfortunately our Cisco 4948 and 4506 do not have stacking. So let me try out in a Lab regarding load balancing using PVST.

Thank you guys for all your suggestions.

Thanks

Arabinda

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