Aggressive Load Balancing
Enabling aggressive load balancing on the controller allows lightweight access points to load balance wireless clients across access points. You can enable aggressive load balancing using the controller.
Note |
Clients are load balanced between access points on the same controller. Load balancing does not occur between access points on different controllers. |
When a wireless client attempts to associate to a lightweight access point, association response packets are sent to the client with an 802.11 response packet including status code 17. The code 17 indicates that the AP is busy. The AP does not respond with an association response bearing 'success' if the AP threshold is not met, and with code 17 (AP busy) if the AP utilization threshold is exceeded, and another less busy AP heard the client request.
For example, if the number of clients on AP1 is more than the number of clients on AP2 plus the load-balancing window, then AP1 is considered to be busier than AP2. When a client attempts to associate to AP1, it receives an 802.11 response packet with status code 17, indicating that the access point is busy, and the client attempts to associate to a different access point.
You can configure the controller to deny client associations up to 10 times (if a client attempted to associate 11 times, it would be allowed to associate on the 11th try). You can also enable or disable load balancing on a particular WLAN, which is useful if you want to disable load balancing for a select group of clients (such as time-sensitive voice clients).
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Voice Client does not authenticate when delay is configured more than 300 ms. To avoid this configure a Central-Auth, Local Switching WLAN with CCKM, configure a Pagent Router between AP and WLC with a delay of 600 ms (300 ms UP and 300 ms DOWN and try associating the voice client |
Passive scanning clients will be able to associate to an AP irrespective of whether load balancing is enabled or not.
Note |
Cisco 600 Series OfficeExtend Access Points do not support client load balancing. With the 7.4 release, FlexConnect access points do support client load balancing. |
You can configure the controller to analyze the WAN interface utilization of neighboring APs and then load balance the clients across the lightly loaded APs. You can configure this by defining a load balancing threshold. By defining the threshold, you can measure the WAN interface utilization percentage. For example, a threshold value of 50 triggers the load balancing upon detecting utilization of 50% or more on an AP-WAN interface.
Note |
For a FlexConnect AP the association is locally handled. The load-balancing decisions are taken at the Cisco WLC. A FlexConnect AP initially responds to the client before knowing the result of calculations at the Cisco WLC. Load-balancing doesn't take effect when the FlexConnect AP is in standalone mode. FlexConnect AP does not send (re)association response with status 17 for Load-Balancing as Local mode APs do; instead, it first sends (re)association with status 0 (success) and then deauth with reason 5. |
This section contains the following subsections: