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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Roaming and DHCP relay on Multiple VLAN configuration

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  • 1.  Roaming and DHCP relay on Multiple VLAN configuration

    Posted Feb 28, 2015 10:09 PM

    Hello,

    we have multiple L2 VLANs configured  [mobility is disabled], which are connected via a trunk to a router that relays to an external DHCP server.

    I am trying to figure some details on the DHCP process while the client is roaming.

     

    At moment of the roaming, a user has an IP on VLAN 1 and he associates to another AP which is offered to use VLAN2.

    Just after the association:

    Will the client reset his IP and start the DHCP process with DHCPDISCOVER?

    or

    Will get connected to VLAN 2  and while still having his VLAN1 IP send a DHCP REQUEST?

    Then get NO from DHCP server and re-initialise DHCP lease process?



  • 2.  RE: Roaming and DHCP relay on Multiple VLAN configuration
    Best Answer

    Posted Mar 01, 2015 06:44 AM

    What happens is dependant on the client type.  Generally the device will be continually arping for their gateway. When there is no response, they will reip. Im not sure if that initially is a unicast RENEW or broadcast DISCOVER.

     

    How quick that all happens does depend on the client. Windows is relatively quick. Android takes a lot longer, and some clients will simply never reip.



  • 3.  RE: Roaming and DHCP relay on Multiple VLAN configuration

    Posted Mar 01, 2015 07:20 AM
    Macs tend to hold on to their IP especially on ML and Yosemite. 


    Thanks, 
    Tim