C9800 WLC: command to force access points migrate to another WLC

[Andrey128]

I have two WLCs configured as N+1 redundancy.

All access points are configured to use WLC1 as primary and WLC2 as secondary per "high availability settings" on each of access point.

Some access points are joined to WLC2 though. How can I force them to join WLC1?

What is the logic on WLC / access points: will they stick to the same WLC till they will be rebooted or lost connection to the currently connected WLC?!

[Kasun Bandara]

try to configure primary WLC in AP as what you want to use as a first WLC. use secondary to second WLC. if you have configured WLC preference, it will connect to primary WLC at first try. 

check this https://www.cisco.com/c/en/us/td/docs/wireless/controller/8-2/config-guide/b_cg82/b_cg82_chapter_01110111.pdf

[Andrey128]

it is already configured that way: connect to WLC1 as primary and WLC2 as secondary, but sometimes some access points connect to WLC2 and stay on it.