Question about uplink (Stacking)

[CATYO]

Hi there.

I have a one question.

In this case,

I think there is one blocked port by STP. Am i right?

if it is ture, can i reduce this blocked port ? what about LACP? Can i configure LACP to this case?

Thank you in advance.

Best regards

[Peter Paluch]

Hi Eunseok,

I think there is one blocked port by STP. Am i right?

Yes, that is correct.

can i reduce this blocked port ? what about LACP? Can i configure LACP to this case?

Yes, absolutely - this would be a common approach. It even has its own name: Cross-Stack EtherChannel. It is often used to provide for very good resiliency and high availability should any of the cables or one of the two switches in the stack fail. If you create an EtherChannel in this topology, there will be no blocked port at all.

Best regards,
Peter

[Joseph W. Doherty]

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

Peter's answer is spot on if the OP's meaning of stack is one that turns the two "stacked" physical devices into one logical device.  Peter's answer also applies if the two units are a VSS pair.

Besides the advantages already noted by Peter, MEC also often provides more aggregate bandwidth.

Also, MEC doesn't require LACP, but LACP would be a common implementation.

Lastly, if you activate Etherchannel, you may need to adjust the load balancing algorithm being used.