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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Mobility issue

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  • 1.  Mobility issue

    Posted Feb 01, 2012 03:37 PM

    We are running M3 controllers on


    We have two local controllers where all of the APs are terminated.  We installed one of them and the first round of APs.  Then, when we expanded, we brought up the second local controller and added the new APs to the second one.  This meant that each area of our campus has an AP from both controllers.  I designed it this way (even though we have a backup controller) so that if one controller failed, there were other APs still up in the same area.


    However, what this has caused is a mobility issue.  When devices move between APs, our arp table on our switch network shows them getting a new IP address.  This may not be every time.  But, when they move around, it seems it causes the arp table to have multiple entries with different IP addresses and the same mac address.


    Is there something I can do to alleviate this besides moving each area to one controller or the other?  Should the clients even be getting a new IP address just for moving to a new AP?




  • 2.  RE: Mobility issue

    Posted Feb 01, 2012 04:16 PM

    Additional information...


    What is happening is when a client moves between APs on different controllers, the arp update messages are frequent and thus increasing the arp update messages and the Cisco switch's performance is being impacted as well as the ability to look up mac addresses and IP addresses in the arp table - and have an accurate view.


    I hope this makes sense.

  • 3.  RE: Mobility issue

    Posted Feb 01, 2012 05:17 PM

    Are the user VLAN pools the same on both local controllers?

  • 4.  RE: Mobility issue

    Posted Feb 01, 2012 05:23 PM

    We are not using VLAN pools.  Both controllers have an IP on VLAN 14 where the users reside.

  • 5.  RE: Mobility issue
    Best Answer

    Posted Feb 01, 2012 05:23 PM
    • You dont have to deploy AP terminating on different controllers in the same area to provide redundancy.
    • You should enable redundancy between your local controller, so that when the primary controller goes down the APs in that location failover to the other local controller that is terminating APs. So you have 2 locals that terminate their APs and act as backup to each other during failure.
    • You should enable IP mobility between the controller so that you dont re-IP when you move between the controllers. Depending on your network design you can use VLAN mobility too.

    See the campus networks VRD at http://www.arubanetworks.com/pdf/technology/VRD_Campus_Networks.pdf for proper design that will solves your current issues.