Does AP's get configuration when the standby tunnel becomes active in HA?
In HA, the AP's are designed to accept configuration only from the lms-ip address.
In the case of lms-ip address not reachable, the standby GRE tunnel will become active but AP will not accept any configuration.
To make any configuration changes, AP has to be pointed back to the lms-ip address.
If preemption is not enabled and when the lms-ip address was not reachable. Standby GRE tunnel for the AP's will become active.
AP's will not fallback to the lms-ip address as preemption was disabled and we need to reboot the AP's to point it to the lms-ip address.
So, its recommended to enable preemption in HA.