Wireless Access

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Access network design for branch, remote, outdoor and campus locations with Aruba access points, and mobility controllers.
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Doubt about AP LB process

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  • 1.  Doubt about AP LB process

    Posted May 07, 2020 03:34 PM

    Hi community,

     

    I am going to deploy a network which consist of two MC 7205 and around 40 RAPs. According to the ArubaOS 8.5.0.0 user guide, the Active AP Rebalance Threshold and the Active AP Unbalance Threshold must be met, and the default values are 20% and 5%, respectively.

    This leads one of the MCs will have to reach around 52 APs to trigger the AP load balance since

     

    Active AP Rebalance Threshold = Active AP load / Platform capacity

     

    Then

     

    Active AP load = Active AP Rebalance Threshold x Platform capacity = 256 x 0.2 = 51.2

     

    Because my network consist of 40 RAPs, does that mean I won't have AP LB between the two MCs with the default values? Then all my APs wil terminate the active tunnel in one of the MCs?

     

    Regards,

    Julián



  • 2.  RE: Doubt about AP LB process
    Best Answer

    Posted May 07, 2020 04:42 PM

    Active AP Rebalance Threshold=20% means a minumum total load % required to do AP LB.

    On a 7205 that support 256AP this means that 20% is hit at 52 accesspoints at one controller.

     

    Active AP Unbalance Threshold 5% means a difference between most and least loaded MC

     

    ClientMatch balances the load periodically, when total load exceeds the minimum load threshold, and the difference between the most and least loaded controller is greater than the Unbalance Threshold.

     

    With 40 RAPs the first criteria doesn't meet the Active AP Rebalance Threshold of 20%, both criteria must be met.

     

    You can lower the active AP Rebalance Threshold to a lower number in your case.

     



  • 3.  RE: Doubt about AP LB process

    Posted May 07, 2020 05:30 PM

    Hi Marcel,

     

    Yes that's what I believe exactly. Then with around 40 APs and if I want the cluster starts the load balancing from 15 APs on, I would need

     

    Active AP Rebalance Threshold = Active AP load / Platform capacity = 15 / 256 = 6% aprox.

     

    Is correct my reasoning?

    Thanks for your interest

     

    Regards,

    Julián



  • 4.  RE: Doubt about AP LB process

    Posted May 07, 2020 06:02 PM

    Yes that will work.



  • 5.  RE: Doubt about AP LB process

    Posted May 08, 2020 07:34 PM

    Hi Marcel,

     

    One more doubt about this, ArubaOS 8.5.0.0 user guide says: 

     

    The periodic load re-balancing occurs every 1 minute, which is the default value and APs are considered for load re-balancing based on AP count, which is 50 by default.

     

    What's the meaning of "based on AP count, which is 50 by default."?

     

    Regards,

    Julián



  • 6.  RE: Doubt about AP LB process

    Posted May 09, 2020 06:52 AM

    When initially loading the cluster, the cluster leader will distribute the incoming AP load using the 1% capacity rule when assigning the AAC.

    Later on, after the cluster is loaded and if there are events that take place, like cluster join or split, changes to the LB thresholds, additional AP load that lead to an imbalance, the LB algorithm gets triggered by the Active AP rebalance (20%) and unbalance (5%) thresholds to redistribute the AP load.

     



  • 7.  RE: Doubt about AP LB process

    Posted May 09, 2020 11:50 AM

    OK makariosm,

     

    But where the parameter "AP rebalance count" takes place? What's the meaning of this parameter?

     

    Regards,

    Julián



  • 8.  RE: Doubt about AP LB process

    Posted May 09, 2020 03:26 PM

    When the LB algorithm is triggered to balance the AP load, it will consider X number of APs to move as a first rebalance attempt. This X number is the 'AP Rebalance count'.

     



  • 9.  RE: Doubt about AP LB process

    Posted May 09, 2020 10:58 PM

    Then, for example, if there is a member failure and the Active AP Rebalance Threshold and Active AP Unbalance Threshold are met, AP LB will trigger but no more than "AP rebalance count" APs (50 by default) will be moved from the member with maximum active load percentage to the other members? Is that?

     

    Regards,

    Julián



  • 10.  RE: Doubt about AP LB process

    Posted May 10, 2020 01:57 AM

    'AP Rebalance Count' at a time and repeated until the balance is restored (i.e. AP Rebalance and Unbalance drop below the thresholds).