We have two WLCs running software version v7.6, and are going to upgrade them to v8.0. The APs joined to each controller have the local one listed as their primary and the other listed as secondary, providing failover should either controller fail.
The two controllers service APs in different buildings, and we would like to undertake the upgrade in two stages as part of our change control process i.e. WLC1 on one evening and WLC2 on another. We have pre-downloaded the new v8.0 software on the controllers and APs in readiness.
On previous upgrades we've noticed that although the APs are pre-downloaded with the new code and set to reboot along with the controller they are currently joined to, depending on how quickly the APs come back up they may try to join their secondary controller (old code). Ideally the upgraded controller would come up before the APs that have been reset, and the pre-downloaded APs would happily re-join their primary controller on their new code. As this isn't always the case, the pre-downloaded AP with new code can't join the upgraded controller immediately (as it hasn't finished rebooting), and starts to look for and joining to it's secondary controller (still running old code). In this instance the pre-downloaded AP/s with new code start the download process from the only available controller (still running the older code), and then HA themselves back across to their primary (on the new code) when the upgraded controller has finished coming up, forcing a second downloading of code for the APs.
Is there a technique where downtime can be minimised through delaying the reboot of the pre-downloaded APs at the same time the controller to be upgraded is rebooted? This would be the only way that I can see it possible to prevent the possibility of the pre-downloaded APs coming up before the upgraded controller being rebooted; resulting in the APs bouncing between the two controllers with multiple code downloads.
Any thoughts would be most appreciated.
Tim
