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Etherchannel one switch to stack switches bandwidth

Hi.

 

Can someone please advise if we have one switch connected physically to two switches which are in a stack, will the bandwidth double or not?

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The Author of this posting offers the information contained within this posting without consideration and with the reader's understanding that there's no implied or expressed suitability or fitness for any purpose. Information provided is for informational purposes only and should not be construed as rendering professional advice of any kind. Usage of this posting's information is solely at reader's own risk.

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Posting

Yes and no because you will have twice the aggregate/available bandwidth but any one flow will only use one link.

Also how well multiple links are utilized depends on your traffic relative to the hashing algorithm.

For dual Etherchannel, expect an effective aggregate increase starting at about 50%.  (Why not full doubling?  Well Etherchannel doesn't account for link loading.  Given two links and two flows, the second flow has a 50% chance of being assigned to the same link as the first flow.  More flows, though, should distribute across the links so your aggregate utilization should improve.)

PS:

Although the bandwidth increase might not be exactly what you desire, for multiple flows you do normally get more effective bandwidth, and especially when working with stacks (or VSS or vPC), you get some additional redundancy too.

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Super Bronze

DisclaimerThe Author of this

Disclaimer

The Author of this posting offers the information contained within this posting without consideration and with the reader's understanding that there's no implied or expressed suitability or fitness for any purpose. Information provided is for informational purposes only and should not be construed as rendering professional advice of any kind. Usage of this posting's information is solely at reader's own risk.

Liability Disclaimer

In no event shall Author be liable for any damages whatsoever (including, without limitation, damages for loss of use, data or profit) arising out of the use or inability to use the posting's information even if Author has been advised of the possibility of such damage.

Posting

Yes and no because you will have twice the aggregate/available bandwidth but any one flow will only use one link.

Also how well multiple links are utilized depends on your traffic relative to the hashing algorithm.

For dual Etherchannel, expect an effective aggregate increase starting at about 50%.  (Why not full doubling?  Well Etherchannel doesn't account for link loading.  Given two links and two flows, the second flow has a 50% chance of being assigned to the same link as the first flow.  More flows, though, should distribute across the links so your aggregate utilization should improve.)

PS:

Although the bandwidth increase might not be exactly what you desire, for multiple flows you do normally get more effective bandwidth, and especially when working with stacks (or VSS or vPC), you get some additional redundancy too.

Hi @babislakatas,It will if

Hi @babislakatas,

It will if EtherChannel is correctly configured between your switch and the stack. At the end, the stack is like a single logical switch so the EtherChannel would be between "two switches".

HTH.

Don't forget to rate.

Rgrds,

Martin, IT Specialist

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