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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Two MDs: Pre-emption is not working.

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  • 1.  Two MDs: Pre-emption is not working.

    Posted Oct 15, 2018 04:34 PM

    Can anyone help to see why the pre-emption is not working?

    1. AP connected to the master MD,

    2. the master MD failed,  AP failed over to the backup MD.

    3. AP stayed connecting with the backup MD and did not go to connect to the Master MD unless rebooting AP.

     

    Thank you!

     

    Here are config for two managed devices.

    (OAW-4750XM-2) #show vrrp


    Virtual Router 12:
    Description mc-vrrp
    Admin State UP, VR State MASTER
    IP Address 172.16.0.241, MAC Address 00:00:5e:00:01:0c, vlan 1
    Priority 110, Advertisement 1 sec, Preemption Enable Delay 30
    Auth type PASSWORD, Auth data: ********
    tracking is not enabled
    (OAW-4750XM-2) #

     

    (172.16.0.252) #show vrrp


    Virtual Router 12:
    Description mc-vrrp
    Admin State UP, VR State BACKUP
    IP Address 172.16.0.241, MAC Address 00:00:5e:00:01:0c, vlan 1
    Priority 100, Advertisement 1 sec, Preemption Disable Delay 0
    Auth type PASSWORD, Auth data: ********
    tracking is not enabled
    (172.16.0.252) #

     

     



  • 2.  RE: Two MDs: Pre-emption is not working.

    Posted Oct 15, 2018 05:59 PM

    What version of AOS are you running? Is there a Mobility Master?

     

    How are the APs discovering the master controller IP? ADP, DNS, DHCP, or static?

     

    To clarify your question, is VRRP pre-emption not working, or has the master for the virtual IP moved back to OAW-4750XM-2 and the APs have not moved with it?



  • 3.  RE: Two MDs: Pre-emption is not working.

    Posted Oct 15, 2018 06:05 PM

    Thank you for your help!

    1. version: 8.3.0.0

    2. there is a mobility master

    3. AP discovers the controller by Static IP (VIP)

    4. virtual IP moved back to OAW-4750XM-2 and the APs have not moved with it.

    Best regards,

     

     



  • 4.  RE: Two MDs: Pre-emption is not working.

    Posted Oct 16, 2018 10:55 AM

    Are the two MDs part of a cluster? 



  • 5.  RE: Two MDs: Pre-emption is not working.

    Posted Oct 16, 2018 11:13 AM

    Yes, thanks!



  • 6.  RE: Two MDs: Pre-emption is not working.
    Best Answer

    Posted Oct 16, 2018 11:19 AM

    @BCroll wrote:

    Yes, thanks!


    Because the two controllers are clustered, this makes sense.

     

    The discovery methods (DNS/DHCP/Static/ADP/etc) are used to discover some/any node in the cluster. Once that node is contacted, the AP downloads the nodelist with all the IPs for controllers in the cluster. This nodelist contains the physical IPs, not virtual-IPs. The cluster leader also determines the APs anchor and standby anchor controller, and the AP builds tunnels to both.

     

    In the case of clustering, the VIP from VRRP is used solely for discovering the cluster. AP tunnels do not use the VIP. The VIP adds robustness to prior discovery methods to ensure that as long as any controller in the cluster is active, APs will be able to discover the cluster.