Distribution to 5x48Port Access switches - uplinks/stacks?

[AdrianBevan9304]

All,

I have a project to replace an existing collapsed core/distribution & access layer, currently in  a single stack.

Core/Dist is 2x3750-12S.

Access layer consists of 4 x 48 port switches, with a requirement to add another.

I want to split the core/distribution layer into it's own stack firstly - probably 2x3850-24S

Client wants 1G to user ports.

Question is how would you best configure the uplinks and access switches - as a single stack, single switches, multiple stacks?

Regards.

[Mark Malone]

Hi
Your best off using the newer 9ks , more throughput and they will work out cheaper as there newer
We used stack of 3x9300 with power stack cables and dual power supplies for a remote site has been very stable on Everest release, you can get 8x10gb up link mods too

9300 are replacing 3k series so you will get more life out of 9k , uses same software too so nothing new
https://www.cisco.com/c/en/us/products/switches/switch-selector.html


for the user access if the switches are all in the same comms i would stack them and dual power each of them , power stack cables too and then link every switch in the stack back to the 2 core switches thats already in a stack using port-channels , thats only 2 logical devices to maintain in config and everything is in HA , just an option

[AdrianBevan9304]

Thanks for your input Mark, how many interfaces in the port channel would you suggest & which interfaces would you spread them across?

Cheers,
Adrian...

[Mark Malone]

You would want each switch to have a link back up to the core/dist personally that's how i do it , so if you have say 4 switches ,1 link off each access switch with 2 of these links in either core switch to give you full resiliency , then test the load balance of the etherchannel to ensure your using all 4 links for flows or as close as you can get it as an example

The interface choice is really yours but i would use the uplink modules if you have them , if not keep it consistent and use the last ports on each switch or something like that

[AdrianBevan9304]

Thanks Mark

Very useful information, appreciated.


Adrian...

[AdrianBevan9304]

Following up on that, since these are 48 port switches I'd like to keep to approx 24:1 overbooking, so 1g uplink to 1 Dist & a second to the other dist - (per switch) would both links be used? would that be a single port channel or two (one to each dist)?

[Mark Malone · Accepted solution]

Yes thats why its a good idea to use 10GB uplink modules between access and dist if possible , the modules are not dear on a 9k as an extra but remember too not all ports will be firing at the same time , if these are just access users you should be ok but if you putting servers in access layer too then may have an issue with oversubscription

10 links may bit overkill if thats what your thinking , 2 POs definitely would be as only 1 PO can be active at a time , the second 1 will automatically go into blocking mode at layer 2 to prevent a loop

my opinion would be a 3gb -5gb link between the dist and access would do fine if just users at the access layer , they wont all be sending traffic at once and if required you can push up to 8 links in a PO and increase it , you can get all links in a PO to send traffic and increase overall bandwidth between the 2 sets of stacks


explains LB on etherchannel
https://www.cisco.com/c/en/us/support/docs/lan-switching/etherchannel/12023-4.html

[AdrianBevan9304]

Thanks Mark, looks like I've got some reading to do....
Most useful.

Adrian...