Wireless Access

I need to change my current Master Controller to a different controller, which is currently running as a Local in this environment. I have read some of the posts and have been able to answer some questions, but I still have other questions. 

My environment is a single Master located in one city, and approx. 45 Local controllers located in 40 cities. We have APs terminated to each local controller at the site they are installed in. 

We are running 6.4.2.6, which I want to upgrade after we move this. 

For the actual process, I undersand that I just convert the Local to Master and then reboot it. There are no APs terminated to this controller currently, as it is configured to be a standby Master in case the main Master failed. 

We are running centralized licensing, and this is my main concern. If I make this new controller the Master, will my licenses transfer over, or will all of my Local controllers and APs need to be rebooted (all 600+ APs) in order to work properly? The way I understand this works is that each Local requests a certain amount of licenses from the Master and the Master just keeps a record of how many are left. 

Also, once I make the new Master, do I just need to go to each Local Controller and type in the new IP of the Master? Will the controller needs to reboot before it will make the GRE tunnel to the new Master?

On a scale of 1-10, how difficult is this whole procedure with respect to overall downtime and service interruptions?

If you make that second controller a backup master to the existing master, you would solve a decent amount of your concerns.

Making the spare controller a backup master to the existing master will make it a backup licensing master, as well.  To be clear, configuring a controller as a backup master (master redundancy) requires special configuration above making it just a local controller.  You would then have to allow them to synchronize their configurations and licenses and then the first master would be able to be removed.

At most, you might have to change the new master's ip address to be the ip address of the old master, when you remove the master from the equation.  In addition, you would have to set a local controller ipsec key on the new controller to match whatever the master had, so that the existing controllers will terminate on that new master controller successfully.

The issue with making a VRRP backup master is that the new Master controller is located in a different physical location and not on the same subnet as the current master. I think this prevents me from setting a automatic backup master like you suggest. 

EDIT: Actually, we have VRRP set up between our current Master and another backup Master located at the same physical location. What I am needing to be done is decommission these two Master controllers, and create a new set of Master controllers located in a different physical location.

If that is possible still, would that be done in the Advanced Services -- Redundancy section? 

You say that the new master is in a new location and going a different subnet.  Are you planning on using the same IP or different? 

If you use a different IP, aren't you going to have to go into each local and reprovision/demote to the new master?  That will require a reboot of the local.

As far as licensing goes, the licenses are tied to/encrypted to the serial number of the controller.  If you are using centralized licensing and have licenses on your locals being pooled up to your master, that isn't a problem, but if your licenses are on your existing master, you're likely going to need to using the licensing site and transfer them to the new controller.

It would be a new IP address on a different subnet. Since that is the case, I would have to reboot all local controllers. 

From  my understanding, if the Master is offline for a bit until I can get to all of the local controllers, the local sites will still continue to operate as normal, yes?

For licensing, I will have to work on transferring all licenses over to the new Master.