Nexus 5548 back to back vPC set spanning-tree priority

[as00001111]

Hey all,

there are two nexus 5548 in a vpc domain that are connected to another pair of nexus 5548 that are also in a vpc domain.

On both vpc pairs are other virtual port-channels where hosts are connected to. But there are also switches and hosts connected without a virtual port-channel.

I need to set the spanning-tree priority of 8196 on the first pair of N5K.

My first thought was just to set the spanning-tree priority on the primary switch.

Then I read about peer-switch.

But I'm very unsure how to solve it since I don't want to bring the network down.

Can someone give me advice?

Thank you!

[lovsharm]

First vpc pair you can keep with same priority, If you have vpc peer-switch command on it and then keep it higher on lower vpc pair but same on both device in one vpc domain with peer-switch. Make sure you use different vpc domain in dual sided vpc side.

[as00001111]

to make sure that I understand you correctly:

on N5K1 and N5K2 I configure vpc peer-switch.

Furthermore I set the spanning-tree priority on both of them. Or only on one of them?

[lovsharm]

let's say 5k1===5k2 are vpc pair. you can use lower priority on both but with peer-switch you need to have the same STP priority on the the vpc pair.

for vpc domain1 keep stp priority lower but same on 5k1 and 5k2 if peer-switch is enable.

for vpc domain2 keep stp priority higher then domain 1 but same on 5k3 and 5k4 if peer-switch is enable.

[as00001111]

Thank you for the explanation.

atm, there is no "peer-switch" configured.

Is it useful to configure it? Does it have any impact to the network or on the vpc members?

[lovsharm]

you can use https://www.cisco.com/c/en/us/support/docs/routers/7000-series-routers/116140-config-nexus-peer-00.html

it is same for n5k.

regards,

Lovkesh

[as00001111]

I read the article but I don't understand what would be the benefit to use peer-switch?

[lovsharm]

you can consider that it's good to have it for STP fast convergence. so configure it. 

[as00001111]

Thank you for your help so far, I'm going to try it and will report back.