We are using two CISCO 5508 WLC and CIsco 3500 series access points.Recently we have upgraded our one WLC on 220.127.116.11 and other WLC is running with OLD IOS image 18.104.22.168.
We are doing testing with 22.214.171.124 on a single wlc and moved some AP on this WLC with newer version.Everything was working fine since last sunday .But on this weekend , Newer IOS WLC got restarted and in the meantime all AP registered on this WLC has moved to old IOS versioned WLC.
As we know , during this transition it delete the HREAP VLAN mapping configuration therefore we have faced the downtime.
My question is , we have only givent the one WLC name and IP address in wiress>HIgh AVailabilty so why my all AP moved to older WLC ?
Do you have mobility group configured with both wlc's? Is the AP's on the same subnet as the WLC? Do you have DNS or option 43 configured? Any of these can help an AP find a WLC. The high availability doesn't matter if you are using any of the above.
Take a look at this doc as it will explain what the ap goes through to find an available WLC.