What must be configured on the Global Configuration page of the WLC for an AP...

On the Global Configuration page of a Wireless LAN Controller (WLC), for an Access Point (AP) to use IEEE 802.1X for authenticating to the wired infrastructure, it is necessary to configure a RADIUS shared secret. This secret will be used by the AP as part of its credentials when communicating with a RADIUS server during the authentication process. References: (CCNP Enterprise Wireless Design ENWLSD 300-425 and Implementation ENWLSI 300-430 Official Cert Guide)