AP no longer join to wlc c9800 after trying join to other wlc

[interfacedy]

Hi, AP c9100 were able to join wlc c9800 with version 17.5. and then the ap got latest ios version 17.5. However, after the ap was trying to join another wlc with version 8.10, the ap is no longer able to join the same wlc c9800. and I notice the ap version is changed to 8.10 from 17.5. Please see the below of some of output of command show version. even factory config cannot work. Not sure how to use backup image that it has. Anyone has some suggestions? Thank you

[Leo Laohoo]

Factory reset the AP.

[interfacedy]

Thank you Leo. Factory reset does not work.

[Leo Laohoo]

Post the complete output to "sh version".

[Scott Fella · Accepted solution]

How did the ap join the 9800 and then join the AireOS controller? Understanding why it happens will help from preventing this from happening in the future.
Now if the ap has joined an AireOS controller successfully, then go define the high availability and point the ap to the 9800 as the primary controller. If the ap doesn’t join, then you need to look at other variables. If you don’t have any aps joined to the 9800, maybe the issue is with your setup and you need to dig in and look at what was possibly missed.

[interfacedy]

Hi Scott, thank you for your reply. I was trying to reply Leo post with output of command show version many times, but failed to post.

However, i suddenly remember i did some change on the vwlc. so it might be vwlc issue. after rebuilding a new vwlc, it started to work.

Now i want to know why the first vwlc cannot work. i remember i changed interface of the vwlc, which might related with certificate, i am not sure. Anyway issue resolved. 

[Scott Fella]

Wireless management is tied to an interface you defined and yes the certificate Is defined to that interface especially on the 9800-CL.

[interfacedy]

I would like to make the first wlc work, do you have document link to show how to handle the issue if I want to change interface and take care of the certificate at the same time? 

[Scott Fella]

What I would do, is review the document you used to setup the 9800-CL. From there you can see the steps what you need to do when you create the management interface and define the wireless interface. That is the process you need to follow again. Now, if you are having a hard time figuring it out, then it’s faster to build a new VM with the correct information.

[interfacedy]

Thank you Scott!