Joining 3802s to a 2504/5508/5520 after it has been on a 9800

[denneht]

Scenario:

We rented a building that already has a ceiling full of 9800s.  When we took occupancy, everyone thought the 3802s would join the 5520.  Nope.

I put a borrowed 9800-l online, and APs would join it.  Reconnect them to the network where the 5520 is, and nope.

Took a 3802 and put it on the bench with my 9800 and it joins.  Connected a 3504 and disconnected the9800.  AP joins the 3504.  Connect the 2504, and disconnect the 3504. Nope.  They won't join.

Oddly, I have a few 2504s on the bench and they have 3802s on them.  it is almost as if the 3802 has been on a 9800, the AP won't ever go back to a 2504.

I cannot seem to find anything posted where anyone has this scenario - where they are moving 3802s back down to a legacy controller.  

Anyone have a link, or possibly some advice?

Thanks!

[denneht]

marce1000, you are a genius!  I believe you have discovered the problem.  Exactly what I thought to be completely honest, but I could not find that post.  I'm going to be testing it, but I think it will suffice.  I have a 3504 running 8.5.182.105, so what I can do it bring it upon the 3504, then plug them into the network where the 8.5.171.0 controller is and see if they downgrade again to the version I need them to be.

[marce1000]

   - FYI (added reply) : https://community.cisco.com/t5/wireless/is-it-possible-to-revert-an-ap-2800-back-from-ios-xe-to-aireos/m-p/4576986#M239931

 M.

[denneht]

Do we know if we downgrade the AP to a controller running  8.10.162 or later, or 8.5.176.2 or later 8.5 code, can we then jump from either one of those versions of code down even further to a production 8.5.171.0 controller?

Meaning, I inherited a ceiling full of 3802s that were on a 9800, but we just occupied the space and they left the APs for us.  Our WLC is a 5520 on 8.5.171.0.  Thinking that I might be able to throw a temporary switch and controller in the rack and patch the APs to it so they downgrade to 8.10.162.0.  Then patch them over to the network with the 5520 and hopefully they will now join that WLC and downgrade themselves to the version that is running.  For reasons out of my control, I cannot jump that 5520 to a later version.

[marce1000]

  >...Do we know if we downgrade the AP to a controller running  8.10.162 or later, or 8.5.176.2 or later 8.5 code, can we then jump from either one of those versions of code down even further to a production 8.5.171.0 controller?
                 - I don't think so ; because then you bump into the same problem

            >...For reasons out of my control, I cannot jump that 5520 to a later version.
  - The problem here is  that it puts you in a 'double showstopper' : One is the exotic downgrade to aireos , and two the 5520 version problem because these days also as the aireos based controllers are being phased out they  should be able(s) to use the last available release.
     Looking at both items the more ideal solution would be  the ability to stay and move forward to the new/modern  9800 platform(s) and models ; you can already download the virtual 9800 platform for free (but would need  DNA-C licenses for the APs...)

 M.