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.
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).
The maximum number
of client associations that the access points can support is dependent upon the
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
Association Limits for Lightweight Access Points are as follows:
number of client associations differs for lightweight and autonomous Cisco IOS
There may be a
limit per radio and an overall limit per AP.
AP hardware (the
16-MB APs have a lower limit than the 32-MB and higher APs)
The maximum Client
Association Limits per-radio for all of the Cisco IOS APs is 200 associations.
For 16-MB APs,
the limit is 128 clients per AP. This limit is applicable to 1100 and 1200
For 32-MB and
higher APs, there is no per-AP limit.
The maximum Client
Association Limits per Autonomous Cisco IOS access point is around 80 to 127
clients per AP. This number varies depending on the following factors:
With 32-MB and
higher lightweight Cisco IOS APs, with two radios, up to 200 + 200 = 400
associations are supported.
(whether it is 16 MB or 32 MB or higher)
configuration (two radios use more memory than one)
(WDS functionality in particular)
The per-radio limit
is about 200 associations. One association will likely hit the per-AP limit
first. Unlike Cisco Unified Wireless Network, autonomous Cisco IOS supports
per-SSID/per-AP association limits. This limit is configured using the
max-associations CLI, under dot11 SSID. The maximum number is 255 associations
(which is also the default number).
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.
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.