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.
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 responds 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 reached or 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).
clients will be able to associate to an AP irrespective of whether load
balancing is enabled or not.
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.
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
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.