http://www.cisco.com/en/US/products/ps6366/products_tech_note09186a00808f8599.shtml
http://ry.tl/lap.html
“This sequence of events must occur in order for an LAP to register to a WLC:
1. The LAPs issue a DHCP discovery request to get an IP address, unless it has previously had a static IP address configured.
2. The LAP sends LWAPP discovery request messages to the WLCs.
3. Any WLC that receives the LWAPP discovery request responds with an LWAPP discovery response message.
4. From the LWAPP discovery responses that the LAP receives, the LAP selects a WLC to join.
5. The LAP then sends an LWAPP join request to the WLC and expects an LWAPP join response.
6. The WLC validates the LAP and then sends an LWAPP join response to the LAP.
7. The LAP validates the WLC, which completes the discovery and join process. The LWAPP join process includes mutual authentication and encryption key derivation, which is used to secure the join process and future LWAPP control messages.
8. The LAP registers with the controller”
