How to get rid of an old controller that a partner is currently using

[JWHolm81891]

I work for a municipality, and I am trying to decommission our old 5500 controller and migrate/update all our of APs to our 9800 (17.6.2). I have three APs I noticed and finally found that a predecessor had set up for the local university that bought these APs (models) 

 AIR-CAP1532E-A-K9

AIR-AP1572EAC-B-K9

that go to our traffic boxes>>our controller>>their network. The whole reason they piggy-back us was so they wouldn't have to extend their network to where they wanted to place them. Well, those APs aren't compatible with our 9800 and the have a virtual 9800 (17.3.5a) on which they say they manage these APs. My question is, how can I still remove the 5500 and not disrupt our service to the university while still keeping these APs managed either on our 9800 or some other way? 

[pieterh · Accepted solution]

does the external 9800 controller's OS still support these model AP ?
if so, you can configure a primary/secondary controller ip-address pointing to the external controller
-> that will be the primary controller they will register to.
then there should not be any problem when you switch off the 5500

only if this external controller is not reachable, it will try to register using broadcast or other discovery mechanisms (DNS, DHCP, etc)
and may discover your own 9800 controller, registration of course will not succeed because it is not a supported AP
situation returns to normal when the external controller is reachable again

[pieterh]

I need add a warning.
the primary controller configuration will mean you have an access point on your network, that is externally controlled/configured
you may consider this a security issue
if you trust the third party, this solution may be simple and acceptable

[JPavonM]

You can deploy a vWLC running AireOS and move those APs and licenses from 5500 there until they upgrade the AP to a supported model, like AIR-CT1542 or state-of-the-art C9124