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).
Note |
Cisco 600 Series OfficeExtend Access Points do not support client load balancing. FlexConnect APs do support client load balancing. |
Note |
For a FlexConnect AP the association is locally handled. The load-balancing decisions are taken at the controller. A FlexConnect AP initially responds to the client before knowing the result of calculations at the controller. 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:
Configuring Aggressive Load Balancing (GUI)
Procedure
Step 1 |
Choose to open the Load Balancing page. |
Step 2 |
In the Client Window Size text box, enter a value between 1 and 20. The window size becomes part of the algorithm that determines whether an access point is too heavily loaded to accept more client associations: load-balancing window + client associations on AP with the lightest load = load-balancing threshold In the group of access points accessible to a client device, each access point has a different number of client associations. The access point with the lowest number of clients has the lightest load. The client window size plus the number of clients on the access point with the lightest load forms the threshold. Access points with more client associations than this threshold is considered busy, and clients can associate only to access points with client counts lower than the threshold. |
Step 3 |
In the Maximum Denial Count text box, enter a value between 0 and 10. The denial count sets the maximum number of association denials during load balancing. |
Step 4 |
Click Apply. |
Step 5 |
Click Save Configuration. |
Step 6 |
To enable or disable aggressive load balancing on specific WLANs, do the following:
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Configuring Aggressive Load Balancing (CLI)
Procedure
Step 1 |
Set the client window for aggressive load balancing by entering this command: config load-balancing window client_count You can enter a value between 0 and 20 for the client_count parameter. |
Step 2 |
Set the denial count for load balancing by entering this command: config load-balancing denial denial_count You can enter a value between 1 and 10 for the denial_count parameter. |
Step 3 |
Save your changes by entering this command: |
Step 4 |
Enable or disable aggressive load balancing on specific WLANs by entering this command: config wlan load-balance allow {enable | disable} wlan_ID You can enter a value between 1 and 512 for wlan_ID parameter. |
Step 5 |
Verify your settings by entering this command: show load-balancing |
Step 6 |
Save your changes by entering this command: |
Step 7 |
Configure the load balance mode on a WLAN by entering this command: config wlan load-balance mode {client-count | uplink-usage} wlan-id This feature requires the AP to upload its uplink usage statistics to the controller periodically. Check these statistics by entering this command: show ap stats system cisco-AP |