A pair of Nexus 93180YC-FX Connecting to a Stack of 3650s via vPC

[dtran]

Hi everyone ... hope everyone is doing well !!!

I have spanning-tree related questions and looking for inputs/suggestions .. thanks all in advance !!

I am attaching a new pair of Nexus 93180s to a stack of Cisco 3650s via vPC. The Cisco 3650 stack is currently the spanning-tree root on my network and I would like the Cisco 3650 stack to continue be the spanning-tree root when it's connected to the Nexus 93180s. My concern is the Nexus 93180s may become spanning-tree root and cause traffic disruption due spanning-tree convergence. My end goal is to prevent the Nexus 93180 to become spanning-tree root.

Questions,

1. Do I simply change spanning-tree priority on the Nexus 93180s to be higher than the 3650 stack ?

2. Anything in the vPC config on the Nexus 93180s that I need worry about ?

I will eventually promote the Nexus 93180s to be spanning-tree root when I am ready to retire the 3650 stack.

Thanks you all for your help !!!

Danny

[marce1000]

 >...Do I simply change spanning-tree priority on the Nexus 93180s to be higher than the 3650 stack ?

                              Yes, no further worries 'needed'

 M.

[balaji.bandi]

when you configure vPC - you use spanning-tree port type network for STP bridge assurance.

downlink towards edge switch config also make sure you use vPC on port-channel.

vPC best practice  for reference :

https://www.cisco.com/c/dam/en/us/td/docs/switches/datacenter/sw/design/vpc_design/vpc_best_practices_design_guide.pdf

[MHM Cisco World]

Hard so Hard to answer this Q.

[dtran]

Thank you very much for your inputs gents !!! very much appreciate your help !!!

Danny

[MHM Cisco World]

I didnot meaning anything 
BUT 
it really hard 
let explain the issue 
there are two VLAN 
vPC-VLAN and non vPC-VLAN 
for vPC-VLAN the Root config in one vPC Peer and secondary Root config also in Secondary vPC Peer 
the issue come from 
the NSK Peer always make STP of vPC-Link as FWD status 
that no problem if root is one of vPC peer 
but config other SW as Root and as I mention above the vPC-Link is FWD 
this unpredictable and need more analysis how the vPC deal with this case. 
that why I say Hard to answer. 
if I get something I will update you 

[dtran]

Thanks MHM !!! appreciate your help as always !!!

I had a similar scenario a few years ago. I connected a pair of Nexus 7010s to a 6509 via vPC and I am pretty sure I had the Nexus 7010 as root and I don't remember experiencing any issues. That was when I migrate from the 6509 to a pair of Nexus 7010s. 

I am being cautious this time .. just making sure I am not disrupting the business when connecting the new Nexus 9k to a production Cisco 3650 stack. 

Thanks !!!

Danny