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Nexus 9K vPC Switch Changes - peer-switch



I have inherited a pair of Nexus 9ks that are already running in production. Under the vPC configuration, 'peer-switch' is configured. I was reading up on that parameter and it said that the Type 1 parameters for the vPC and switches have to match. Currently when I check the 'show vpc consistency-parameters vlan' or Po1 or global etc, all of them match and we have no issues.


I was planning to make a few changes, like enabling 'spanning-tree port type edge bpduguard default', setting existing port-channels to some servers that are also configured in a vPC with 'spanning-tree port-type edge', adding vlans to those same port-channels, bringing up new vPCs to another set of Nexus switches etc. As soon as I make any of these on one of the two switches in the vPC, won't the vPC either peer-link for global parameters or the individual vPC links to servers be put into suspended state? How is it possible to make changes without bringing down the vPC? 


Do I need a maintenance window every time that I need to add a vlan to the port-channel that is configured as a vPC because the parameters won't match between the two switches until I configure both the same.





You may have to shutdown one vPC peer (i.e shutdown vPC ) and make the changes on the other.
Again I will do it only in a maintenance window
Manoj Papisetty
Cisco Employee

Nexus 9k and vpc work a little smarter than that. You are right about the consistency parameters, that any type 1 consistency parameter conflict would bring down your vpc. Having said that, adding VLANs work very differently.


When you add VLANs to the peer-link itself, only the mismatch VLANs go into suspended state. And once you make the configuration changes to the other switch, this gets cleared out. Which means, there is no traffic impact.


The concept works similarly for the member ports as well. Unless you are messing up things, you should not see impact to existing traffic while bringing up new vlans or new ports.

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