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Cisco recommendation - stack switches

Hi All,

Would like to know the maximum  no. of recommeded switches in a 3750 stack. I know the maximum allowed is 9 but wanna implement the best practice knowing the same.

Please let me know link wherein cisco as mentioned the same.

regards,

VB

7 REPLIES
Cisco Employee

Cisco recommendation - stack switches

Hello Vijay,

To my best knowledge, there is no such recommendation. You can stack as many switches (up to 9) as you need without causing any performance or stability degradation.

Best regards,

Peter

New Member

Cisco recommendation - stack switches

Hi Peter,

Thanks for the reply.

The reason for the post was with the stack of 5 , the average memory utilization is 60-70 % and CPU is 40 % already. If i add few more then memory might rach the peak.

Regards.

VB

Cisco Employee

Cisco recommendation - stack switches

Hi Vijay,

Hmmm... What exact IOS version are you running?

Best regards,

Peter

Cisco recommendation - stack switches

I worked for a company once, that had a stack of 9 3750's. I would not recommend doing this. I would personally recommend a max of 4 or 5. The stack of 9 3750's had all sorts of problems; granted it could have been caused by a bug I suppose. Just my personal opionion.

Super Bronze

Re: Cisco recommendation - stack switches

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Posting

Like, Peter, unaware of any recommendation.  Several years ago, I worked in a environment where (original series) 3750s were occasionally stacked to their max of nine.  Don't recall any notable issues.  However, it you scan these forums, some seem to have issues with large stacks, e.g. like John's post.

Peter mentions no performance degradation.  In our deployment for user edge switches, we didn't see any performance issues, but in theory as stackrings are not fabrics, a large stack may run into stackring performance issues sooner than smaller stacks.  (NB: This is more likely with StackWise vs. StackWisePlus, as the former floods all traffic to the ring.)

BTW, if you're buying new, you might want to carefully compare 4510 series to large 3750 stack.  The 4510 might be less expensive and likely offer better performance.  Also if you're buying new, you might want to examine the new 3850-X series, although at the moment they don't support stacks of more than four units.

Silver

Re: Cisco recommendation - stack switches

I recall working on a 3750E stack acting as a collapsed core/distribution layer. It comprised 7 x 48-port switches. The CLI was very slow to respond. This can be quite un-nerving at times, especially when you enter an important command and nothing happens for a second or two - it seems like eternity! To be fair, it wasn't fit for purpose in my view. Whilst there hadn't been any actual failures, their campus was simply too busy for that topology.

      

VB, also bear in mind your traffic patterns in relation to the stack ring. You can help mitigate this to some degree - i.e. placing top talkers on the same stack member, so that traffic is switched on the local backplane and not the stack ring. You do need StackWise Plus for this though. Legacy StackWise will place all traffic on the ring, even if the ingress and egress ports are on the same stack member.

What's your stack doing at the moment? Is it access-layer, for example?

Hall of Fame Super Gold

Re: Cisco recommendation - stack switches

I'm with everyone here.

I seriously DO NOT recommend a stack of seven and more.  I've set a, reluctantly, maximum limit of six switches in a stack.  My "magic number" is up to five.

And it doesn't matter what IOS version or whether or not your entire stack is a 3750X vs mixed stack.  I've been there, I've done that, and I'm sticking by my recommendation. 

VB:  Can you tell us the different models of the 3750 you will be having in your stack and the IOS version level you'll be using?

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