First, I have to mention that Indeni offers a comprehensive analysis for critical vPC metrics and configuration settings including but not limited to the next:
- vPC type 2 consistency status
- vPC advanced features status such as peer-gateway, vPC graceful consistency check, auto-recovery
- vPC peer link status or any of the members link vPC status
- vPC peer keepalive status
As concerns your question the vPC keepalive link is used as a secondary test mechanism to confirm the vPC peer is live in case the Peer-Link goes down.
In particular it is used as an extra protection mechanism to determine whether the peer link itself has failed or whether the vPC peer is down. It should be clear that neither data nor synchronization traffic is sent over the vPC peer keepalive link but just keepalive packets. The frequency of these packets can be set with relevant configuration change.
So, in your case where the peer keepalive will be temporarily down it will not affect the operation of the vPC. Just take care that the vPC peer links are operational before proceed with the upgrade of the Catalyst switch which is used for the vPC keepalive.
You can also review the article published by Indeni which includes review, configuration, testing of the vPC feature and the analysis offered by indeni.