Cisco 3650 stacking

[bruc3]

Hi,

The company I work for has got 6 x 3650 switches in their cabinet and to my surprise they are not setup in a stack.

To my understanding, this model requires a stack module to be installed to be able to stack them.

I am fairly new to the networking World, but would there be a good reason why these 6 switches would be setup in a non stacked configuration?

Also, since they are already all setup in a production environment, would it be difficult to stack them now?

Lastly, if I stack them now, does that mean I need to wipe all the config first from all 6 switches?

Currently, I am leaning towards possibly just leaving them un-stacked.

[Mark Malone]

hi

I am fairly new to the networking World, but would there be a good reason why these 6 switches would be setup in a non stacked configuration?

it will cost another few thousand just for the stacking cables may have been an reason , might not have had budget

do they all have the same licenses too ?

Also, since they are already all setup in a production environment, would it be difficult to stack them now?

Everything needs to come down full outage , but you could create a stack of 2 first and then add the rest in live , sometimes though if there's an issuing in stack joining members it may reload whole stack  seen it happen before so always ave a window

Lastly, if I stack them now, does that mean I need to wipe all the config first from all 6 switches?

It will become one logical switch config so best of to have the switch wiped first before being being inserted

Currently, I am leaning towards possibly just leaving them un-stacked.

stacking offers a lot more power , throughput , resiliency but yes youll have to take it down to build it

[Jaderson Pessoa]

@bruc3 hello,

I am fairly new to the networking World, but would there be a good reason why these 6 switches would be setup in a non stacked configuration?  ( budget is a good reason )

Also, since they are already all setup in a production environment, would it be difficult to stack them now?

( to stack them it is very simple, but you will need have attemption, because will will need backup configuration of all switches and reconfigure these backup to correctly  module/interface and you will need turn down all of them to do it;

So, you will need a plan to make it.

Regards,

[paul driver]

Hello

Just like to add- You don’t mention how these switches are connected? - are they interconnected to each other or each individually connected to a core switch?

one possible reason why they are NOT stacked could be because you don’t have much horizontal traffic and as such there isnt a need to high backplane usage.

As for stacking them yes you will require stack modules and cabling and you need to select a master switch and configure provisioning for the others -and yes the switches will need to lose their current configuration 

[bruc3]

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Thanks for the help so far guys.

@paul driver wrote:

Hello

Just like to add- You don’t mention how these switches are connected? - are they interconnected to each other or each individually connected to a core switch?

Sorry, i still need to check to confirm how they are connected to each other. I will confirm this tomorrow.

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@paul driver wrote:

one possible reason why they are NOT stacked could be because you don’t have much horizontal traffic and as such there isnt a need to high backplane usage.

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 Can you please explain this in more layman terms? I am not a big networking guy.

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[Joseph W. Doherty]

"I am fairly new to the networking World, but would there be a good reason why these 6 switches would be setup in a non stacked configuration?"

Besides what the other posters have described, since we don't know you physical or logical topology (and application traffic flows), yes there can be other reasons for not stacking the units. For one, by keeping them separate, one IOS is not a single point of failure for all the units. You could also run the units on different IOS versions. The latter could be important if you have need to use some very new feature, which you can limit to some switch units, yet not expose all your units to possible stability issues.

Another reason might be for performance. In a six stack unit, intrastack traffic needs to hop between units, and in theory, the stack ring might congest or impose additional latency. (NB: this is a bit more likely with the 3650 vs. the 3850, as it only has 1/3 the possible stack bandwidth of the 3850.)

[bruc3]

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@Joseph W. Doherty wrote:

Another reason might be for performance. In a six stack unit, intrastack traffic needs to hop between units, and in theory, the stack ring might congest or impose additional latency.

Ah, this makes sense. I guess this could very well be the reason. Unfortunately the person who originally set this up has left the company a long time ago so I cannot ask them the reason.

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[bruc3]

I am also thinking of adding a 3750 POE switch soon, since the current 3650 switches are not stacked, I should have no issues adding the 3750 POE switch?

As the switches are different models, not sure if it will cause any issues.

[Mark Malone]

You cant stack a 3750 to a 3650 , one ios and the other ios-xe wont work , different connectors too
just trunk it off , don't go over 6 switches in a stack anyway its not great practice

[bruc3]

Thanks, I understand.