Chapter 6 Deploying Wireless Networks for FortiOS 5.0 : Access point deployment : Advanced WiFi controller discovery
  
Advanced WiFi controller discovery
A FortiAP unit can use any of four methods to locate a controller. By default, FortiAP units cycle through all four of the discovery methods. In most cases there is no need to make configuration changes on the FortiAP unit.
There are exceptions. The following section describes the WiFi controller discovery methods in more detail and provides information about configuration changes you might need to make so that discovery will work.