You can do the AP load balancing on two or more Wireless LAN Controllers (WLCs) if you configure mobility groups properly. The Lightweight Access Point Protocol (LWAPP) allows for dynamic redundancy and load balancing. For example, if you specify more than one IP address for option 43, an AP sends LWAPP discovery requests to each of the IP addresses that the AP receives. In the WLC LWAPP discovery response, the WLC embeds this information:
- Information on the current AP load, which is defined as the number of APs that are joined to the WLC at the time
- The AP capacity
- The number of wireless clients that are connected to the WLC
The AP then attempts to join the least-loaded WLC, which is the WLC with the greatest available AP capacity. After an AP joins a WLC, the AP learns the IP addresses of the other WLCs in the mobility group from its joined WLC.
Subsequently, the AP sends LWAPP primary discovery requests to each of the WLCs in the mobility group. The WLCs respond with a primary discovery response to the AP. The primary discovery response includes information about the WLC type, total capacity, and current AP load. As long as the WLC has the AP Fallback parameter enabled, the AP can decide to change over to a less-loaded WLC.
Once an AP joins a controller, it only leaves the currently joined controller for a limited number of reasons. For that reason, this load balancing algorithm is only an approximate load balancing algorithm unless you manually define a primary controller for each AP.
Note: Once an access point joins a controller you can assign Primary , Secondary , Tertiary controller . Though it is a manual process it is the best way to Load balance Access Points.
Refer to the Assign Primary, Secondary, and Tertiary Controllers for the Lightweight AP and Configure the AP Fallback Feature section of WLAN Controller Failover for Lightweight Access Points Configuration Example for more information.
Refer to following related documents for information on how to configure the WLC:
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