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Community Member

Etherchannel: Trunking or Not?

Hey there, I was wondering if I could get some advice from the great minds at Cisco. We are currently upgrading our network and was wondering what is better, Trunking through etherchannel or not? I am trying to weight the pros and cons as our network infrastrture includes 2960 and 3750E switches that has L3 to the edge devices with the 6509 hosting some vlans. Should the vlans be hosted on the 6509 and enable trunking on the ethernchannel from lets the 2960 swich? Look forward to your response(s).

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Community Member

Re: Etherchannel: Trunking or Not?

Absolutely use etherchannel (either LACP or PAGP)... It will add redundancy into your network (if one link breaks, it will seamlessly shift all traffic to the other) and when both links are working, it would allow for bonding of connections (2x100mb = 200mb etherchannel, 4x1gb = 4gb etherchannel).

All of your trunking and routing should absolutely (without a doubt) be handled on the 6509, and all of the 2960s/3750s should read the trunk information from the 6509 and pass traffic accordingly.

I did a very similar setup for a customer and found some interesting characteristics of etherchannel, please take a look - it's informative and gives all the configs right there!

Link:

http://www.sleepyshark.com/lacp-pagp-etherchannel-not-working-ec-5-cannot_bundle2/

Thanks,

Sean Brown

http://www.sleepyshark.com

Silver

Etherchannel: Trunking or Not?

blakecrossley wrote:

Hey there, I was wondering if I could get some advice from the great minds at Cisco. We are currently upgrading our network and was wondering what is better, Trunking through etherchannel or not? I am trying to weight the pros and cons as our network infrastrture includes 2960 and 3750E switches that has L3 to the edge devices with the 6509 hosting some vlans. Should the vlans be hosted on the 6509 and enable trunking on the ethernchannel from lets the 2960 swich? Look forward to your response(s).

Etherchannels provide physical redundancy (I.E. separate cables) and additional bandwidth for a given link. Bear in mind that, owing to load balancing methods, you may not get *exactly* your multiplier of bandwidth - 2 x 1 gig links might not get you exactly 2 gig of bandwidth - but you'll get close.

If you have the cable infrastructutre in place, or are able to put it in place, then I recommend ueing an etherchannel for uplinks by all means - especially if your cabling is via diverse paths so that a disaster/outage on one path won't kill your link completely.

As far as your other question goes - the VLAN's have to exist on all devices - the 6509 *and* 2960/3750 switches - which need access to the VLAN concerned, otherwise the trunking won't work properly (no point trunking a VLAN to a switch on which it doesn't exist) - but the SVI (switched virtual interfaces) can easily be located on your 6509, and all layer-3 routing done there - in fact, I'd recommend it, as the 6509 normally has a lot more resources for layer 3 routing than the 2960 or 3750 does. Running layer-3 interfaces (other than for management) on your 2960/3750 switches would lead to more complexity than you would want, usually.

There are, of course, circumstances where you *DO* want layer-3 interfaces on access switches, but not often.

Cheers.

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