Wireless Access

Contributor I

Roaming and DHCP relay on Multiple VLAN configuration


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?


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?

Re: Roaming and DHCP relay on Multiple VLAN configuration

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.

If my post is helpful please give kudos, or mark as solved if it answers your post.

ACCP, ACCX #817, ACMP, ACMX #294
Guru Elite

Re: Roaming and DHCP relay on Multiple VLAN configuration

Macs tend to hold on to their IP especially on ML and Yosemite. 


| Tim Cappalli | Aruba Security | @timcappalli | timcappalli.me |

NOTE: Answers and views expressed by me on this forum are my own and not necessarily the position of Aruba or Hewlett Packard Enterprise.
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