Hello and thanks for the post.
You should always upgrade from the active node assuming this is an active/passive cluster. The upgrade will start and at a point, the system will reboot. The VIP(s) will then fail over to the passive node who will take on the users from the first node. Users may see a small interruption of their tunnel traffic, so be forewarned but they will auotmatically re-establish their tunnel back to the second node. Once the first node reboots and completes the upgrade, it will alert the second node, copy the upgrade package over to it and then start the upgrade there. At the same point, users will fail back over to the first node and reconnect.
On an Active/Active cluster, it really doesn't matter which you upgrade first, but each node will upgrade one at a time so that users can move to the other node(s).
As always, it is highly recommended that you take a user and system config backup BEFORE runnint the upgrade just in case anything happens.
... View more