Hi Konrad,
Have a look at the methods the AP uses to determine which of the WLC's to register to;
WLCs embed this important information in the LWAPP discovery response:
The controller sysName
The controller type
The controller AP capacity and its current AP load
The Master Controller flag
An AP-manager IP address
The LAP uses this information to make a controller selection, with use of these precedence rules:
If the LAP has previously been configured with a primary, secondary, and/or tertiary controller, the LAP examines the controller sysName field (from the LWAPP discovery responses) in an attempt to find the WLC that is configured as primary. If the LAP finds a matching sysName for the primary controller, the LAP sends an LWAPP join request to that WLC. If the LAP cannot find its primary controller or if the LWAPP join fails, the LAP tries to match the secondary controller sysName to the LWAPP discovery responses. If the LAP finds a match, it then sends an LWAPP join to the secondary controller. If the secondary WLC cannot be found or the LWAPP join fails, the LAP repeats the process for its tertiary controller.
The LAP looks at the Master Controller flag field in the LWAPP discovery responses from the candidate WLCs if one of these items is true:
No primary, secondary, and/or tertiary controllers have been configured for an AP.
These controllers cannot be found in the candidate list.
The LWAPP joins to those controllers have failed.
If a WLC is configured as a Master Controller, the LAP selects that WLC and send it an LWAPP join request.
If the LAP cannot successfully join a WLC on the basis of the criteria in step 1 and step 2, the LAP attempts to join the WLC that has the greatest excess capacity.
From this good doc;
http://www.cisco.com/en/US/tech/tk722/tk809/technologies_tech_note09186a00806c9e51.shtml
Hope this helps!
Rob
