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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Vlan Mobility - some queries on how it works.

  • 1.  Vlan Mobility - some queries on how it works.

    Posted Mar 31, 2014 07:10 AM

    Hi,

     

    i have some about 6 vlans, pooled, with even vlan assignment. The controllers are in code 6.1.3.9.

     

    there are about 3 controllers, with all these 6 vlans trunked to the common uplink switch.

     

     "vlan mobility" is not turned on as of now.

     

    There are multiple entries of same mac-address across same vlan. and some same mac-address with different vlans, in the output of show datapath bridge table.

     

    Reference: https://arubanetworkskb.secure.force.com/pkb/articles/HowTo/R-1452

     

    By the above KB, if a controller, looks the show datapath bridge table, which record from the table will be taken for vlan assignment for the vlan-mobile client?

     

    I am in doubt if enabling vlan mobility on a production vap, will be distruptive for the clients. Please advise on this as well.

     

    I want to check if there is a way to clear the show datapath bridge table entries, so there would be new vlan assignments for the clients. please advise.

     

     



  • 2.  RE: Vlan Mobility - some queries on how it works.

    Posted Mar 31, 2014 07:52 AM

    The VLAN is chosen by the VLAN pooling algorithm, NOT the bridge table...

     

    Vlan mobility has nothing to do with what VLAN is chosen in a pool.  If you choose "hash" the VLAN # chosen will always be the same.  Not so with the even pooling algorithm...

     

     



  • 3.  RE: Vlan Mobility - some queries on how it works.

    Posted Mar 31, 2014 12:51 PM

    Thank you CJ. Then what is the purpose and function of vlan mobility? 



  • 4.  RE: Vlan Mobility - some queries on how it works.

    Posted Mar 31, 2014 12:59 PM

    Please search the knowledgebase at http://support.arubanetworks.com/KNOWLEDGEBASE/tabid/133/Default.aspx for "vlan mobility" for tons of information on the topic.  The most common use is if you have two different AP-Groups on the same controller where the Virtual APs have different VLANs configured--Enabling VLAN mobility will allow a client already in the user table, when it roams to an access point that has a VAP with different VLANs to keep the same VLAN...  That is probably the most common use...

     



  • 5.  RE: Vlan Mobility - some queries on how it works.

    Posted Mar 31, 2014 11:49 PM

    Thank you CJ. So in my scnario of multi-controller environment, that is 1 master and 2 local controllers, with their uplinks trunking all the user vlans to a common L3 switch. I should not be using the vlan pooling by even assignment. I should use the hash assignment. Correct? Please advise.

     

     To note: My clients will be moving between APs on all the three controllers. 

     

     



  • 6.  RE: Vlan Mobility - some queries on how it works.

    Posted Apr 01, 2014 04:57 AM

    Yes.

     

    If you have VLANs 3,4,5 on the first, second and third controller, using Hash, your client will always end up in the same VLAN...



  • 7.  RE: Vlan Mobility - some queries on how it works.

    Posted Apr 01, 2014 05:36 AM

    Thank you CJ. To make my understanding better. 

     

    I should use the even assignment in vlan-pooling, only when my topology is a standalone controller, correct? 



  • 8.  RE: Vlan Mobility - some queries on how it works.

    Posted Apr 01, 2014 06:33 AM

    It is not necessarily a best practice to that.



  • 9.  RE: Vlan Mobility - some queries on how it works.

    Posted Apr 01, 2014 09:21 PM

    Thank you CJ. Would you be able to comment, on what may be impact if we have even vlan-pooling assignment, in a multi-controller(master-local) topology?. Where all the vlans are trunked down to a L3 switch, which does the DHCP relay. There are two DHCP servers in this network. where the dhcp scope is slipt and managed by each server. The dhcp scope in one server, is excluded in the other. 



  • 10.  RE: Vlan Mobility - some queries on how it works.

    Posted Apr 01, 2014 09:22 PM

    Is it even possible to roam from an access point on one controller to the other?



  • 11.  RE: Vlan Mobility - some queries on how it works.

    Posted Apr 01, 2014 09:24 PM

    Yes, the client can be moving from AP on one controller to the other. 



  • 12.  RE: Vlan Mobility - some queries on how it works.

    Posted Apr 07, 2014 11:13 PM

    hi yogenpartha,

     

    You definitely do not what to be using even vlan pooling in this situation, it is not compatible with your topology. As client moves from controller A to controller B, it can change vlans, and hence may change IP address. Worst case scenario is if there are APs in same building terminating to two different controllers. The preserve vlan option is tempting to try to use, but it doesnt solve the problem and especially in 6.1.x has some known caveats that further make it a non solution.

     

    regards

    -jeff