Starting from this note in the "Configuring Hybrid REAP" :
If the access point has been assigned a static IP address, it can discover a controller through any of the LWAPP discovery process methods except DHCP option 43. If the access point cannot discover a controller through Layer 3 broadcast or OTAP, Cisco recommends DNS resolution. With DNS, any access point with a static IP address that knows of a DNS server can find at least one controller.
I don't fount where configure the ip address of the DNS server.
Thanks for any help.