Configuring Aggressive Load Balancing
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Configuring Aggressive Load Balancing

This module contains the following topics:

Finding Feature Information

Your software release may not support all the features documented in this module. For the latest feature information and caveats, see the release notes for your platform and software release.

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Restrictions for Aggressive Load Balancing

  • You can configure aggressive load balancing only from the command-line interface.
  • Aggressive load balancing is disabled by default, you have to enable it manually.
  • You can enable load balancing either separately or together with the band select configurations.
  • When the band select is enabled on the dual-band clients, the load balancing parameter selects only the lowest load radio from 5-GHz radios. For the 2.4-GHz clients, there is no probe information of the client on 5 GHz and therefore the load balancing algorithm can only be selected between radio on 2.4 GHz.
  • You can operate load balancing of clients between access points on the same switch but not for the clients between access points on the different switch.
  • The load balancing uses an existing association denial mechanism based on the number of client on the radio and the band select is implemented by the distributed probe response suppression on the access point only.

Information for Configuring Aggressive Load Balancing Parameters

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.

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 are load balanced between access points on the same controller. Load balancing does not occur between access points on different controllers.

The maximum number of client associations that the access points can support is dependent upon the following factors:
  • The maximum number of client associations differs for lightweight and autonomous Cisco IOS access points.
  • 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 Client Association Limits for Lightweight Access Points are as follows:
  • For 16-MB APs, the limit is 128 clients per AP. This limit is applicable to 1100 and 1200 series APs.
  • For 32-MB and higher APs, there is no per-AP limit.
The maximum Client Association Limits per-radio for all the Cisco IOS APs is 200 associations.

Note

With 32-MB and higher lightweight Cisco IOS APs, with two radios, up to 200 + 200 = 400 associations are supported.

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:
  • AP model (whether it is 16 MB or 32 MB or higher)
  • Cisco IOS software release
  • Hardware configuration (two radios use more memory than one)
  • Enabled features (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).

How to Configure Aggressive Load Balancing

Configuring Aggressive Load Balancing

SUMMARY STEPS

    1.    configure terminal

    2.    wireless load-balancing window client-count

    3.    wireless load-balancing denial denial-count

    4.    end

    5.    wlan wlan_profile_name wlan_ID SSID_network_name load-balance

    6.    end


DETAILED STEPS
     Command or ActionPurpose
    Step 1 configure terminal


    Example: 
    Switch# configure terminal
     

    Enters global configuration mode.

     
    Step 2wireless load-balancing window client-count


    Example: 
    Switch(config)# wireless load-balancing window 1
     

    Sets the client window for aggressive load balancing. You can enter a value between 0 and 20 for the client_count parameter.

     
    Step 3wireless load-balancing denial denial-count


    Example:
    Switch(config)# wireless load-balancing denial-count 1
     

    Sets the denial count for load balancing. You can enter a value between 0 and 10 for the denial_count parameter.

     
    Step 4end


    Example:
    Switch(config)# end
     

    Returns to privileged EXEC mode. Alternatively, you can also press Ctrl-z to exit global configuration mode.

     
    Step 5wlan wlan_profile_name wlan_ID SSID_network_name load-balance


    Example:
    Switch(config)# wlan wlan1 25 ssid12
    Switch(config-wlan)# load-balance
     

    Enables or disables aggressive load balancing on specific WLANs

    You can enter a value between 1 and 512 for the wlan_ID parameter.

    You can enter the up to 32 alphanumeric characters for SSID_network_name parameter.

     
    Step 6end


    Example:
    Switch(config)# end
     

    Returns to privileged EXEC mode. Alternatively, you can also press Ctrl-z to exit global configuration mode.

     

    Monitoring Aggressive Load Balancing

    This section describes the new command for aggressive load balancing.

    The following command can be used to monitor aggressive load balancing on the switch.

    Table 1 Monitoring Aggressive Load Balancing Command

    Command

    Purpose
    show wireless load-balancing

    Displays the status of the load-balancing feature.

    Examples: Aggressive Load Balancing Configuration

    This example shows how to configure the load balancing denial count:
    Switch# configure terminal
Switch(config)# wireless load-balancing denial-count 1
Switch(config)# end
Switch# show wireless load-balancing
    This example shows how to configure the client window for aggressive load balancing:
    Switch# configure terminal
Switch(config)# wireless load-balancing window 1
Switch(config)# end
Switch# show wireless load-balancing
    This example shows how to configure load balancing on specific WLAN:
    Switch# configure terminal
Switch(config)# wlan wlan1 25 ssid12
Switch(config-wlan)# load-balance
Switch(config)# end
Switch# show wireless load-balancing

    Additional References for Aggressive Load Balancing

    Related Documents

    Related Topic Document Title
    System management commands

    System Management Command Reference Guide, Cisco IOS XE Release 3SE (Cisco WLC 5700 Series)

    Standards and RFCs

    Standard/RFC Title
    None

    —

    MIBs

    MIB MIBs Link
    All supported MIBs for this release.

    To locate and download MIBs for selected platforms, Cisco IOS releases, and feature sets, use Cisco MIB Locator found at the following URL:

    http:/​/​www.cisco.com/​go/​mibs

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    Feature History and Information For Performing Aggressive Load Balancing Configuration

    Release Modification
    Cisco IOS XE Release 3.2SE

    This feature was introduced.