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New Member

etherchannel confussion

i went thru the lacp and pagp technology and as i have understood, you can bundle or group ports to form a single etherchannel, thus extending your total bandwidth depending on the bundled ports.

as i do further reading on this forum, i came up to the below link on 1 of the answers

http://forum.cisco.com/eforum/servlet/NetProf?page=netprof&CommCmd=MB%3Fcmd%3Dpass_through%26location%3Doutline%40%5E1%40%40.eea1e0b/0#selected_message

i will quote the last paragraph

"At the end of the day, a single flow will only ever traverse a single link of the bundle. The hash just determines which link. Load doesn't come into the equation."

If this is true, then can we conclude that the etherchannel is not doing a truly link aggregation but instead just a form of redundancy which can be achieve without enabling etherchannel?

just confused.

thanks in advance

4 REPLIES
New Member

Re: etherchannel confussion

You are right in concluding etherchannel is mostly link redundancy, it is however giving you some aggregation, the hash will somewhat distribute traffic (based on src/dst mac) on the multiple links of your etherchannel. If you did not use etherchannel to get redundancy, STP would have to be used, and on a link failure STP will be much slower to recover than etherchannel.

New Member

Re: etherchannel confussion

If you are saying that the hash will distribute traffic on the multipple links of the etherchannel, how come on the conclussion of the link ive mentioned above says;

"a single flow will only ever traverse a single link of the bundle. The hash just determines which link. Load doesn't come into the equation."

This is what confuses me.

New Member

Re: etherchannel confussion

A flow is restricted to one link, and to the capacity of that link. But another flow could (depends on hash) use another link of the etherchannel, and that's when you get some overall bandwidth aggregation.

New Member

Re: etherchannel confussion

then we could conclude that

1. a flow is restricted to a single link and

2. multiple flow could exist at any given time.

thx a lot

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