Switch stacking and Etherchannel

[aconticisco]

Hi,

on doing some research I came to a question which I cannot answer so far, when you stack 2 switches together you are effectivly creating a larger single switch (correct if otherwise), so when you connect two switches together via EtherChannel ports aren't you achieving the same thing ?

Differences between these two situations needs clarification please.

Thanks

[Joseph W. Doherty · Accepted solution]

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Posting

No, they are quite different.

Etherchannel allows you to bundle multiple links into one logical link, is roughly somewhat like MLPPP or an ATM inverted mux.

Stacking allows you to bundle multiple independent switches into one logical switch.

You can use both, together, or not.

Etherchannel now has also has an industry standard, LACP.  Stacking is very proprietary and may differ between different devices.  For example, you can stack original generation 3750s, StackWise, with later generation 3750s (E/X models) StackWisePlus, but both won't stack with 2960S, FlexStack, or later 2960 FlexStack-Plus series models, although FlexStack and FlexStack-Plus can stack together.  There's also StackWise-480 for the 3850, which I think only works between them.  There's also, other Cisco devices, VSS, which makes a pair like one, sort of a special dual stack, but interestingly, those use "ordinary" ports, often Etherchanneled, the other stacking technologies use special stacking ports (generally offering more bandwidth).

[aconticisco]

So EtherChannel permits to increase the bandwidth and resiliency between two switches by allowing two or more ports to be setup this way while stacking permits to increase the port density of a switch by having it stacked to another switch.

And as you said you can have stacked switches with EtherChannel setup, did I got it right ?

[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

Yes, but stacking offers other advantages too.  Often "sup" resiliency, and more bandwidth between stack members, and just one logical device instead of many.  The latter also has implications beyond eased management.  For example, no intentional L2 links for redundancy, one L3 device, and no HSRP for the gateway.