Question on 802.11r

[Krishna Chaitanya]

On Tue, Nov 12, 2013 at 3:35 PM, Nicolas Cavallari
<Nicolas.Cavallari at green-communications.fr> wrote:
> On 12/11/2013 10:19, Antonio Quartulli wrote:
>> On Tue, Nov 12, 2013 at 08:54:55AM +0000, michael-dev wrote:
>>> Hi,
>>>
>>> Am 12.11.2013 05:36, schrieb Ben Greear:
>>>> Now, I have a somewhat related question:  Should the station
>>>> re-acquire DHCP lease after successfully roaming? ...
>>>> So, it would be nice to skip
>>>> DHCP, but I'm not sure if that is how real-world networks
>>>> are configured?
>>>
>>> even without 802.11r when devices are roaming within the same SSID, some
>>> don't refresh DHCP after changing the BSSID. I believe a recent version
>>> of MAC OS was doing so and maybe others, though I'm not sure which HW/SW
>>> exactly was used on client side. So that is why I built DHCP-Snooping /
>>> IP+ARP-Filter on my APs in a way that those stations don't loose network
>>> connectivity.
>
> When devices roams, they expect that the layer2 environment is the same.
> They are not required to refresh any DHCP lease or anything.

How does the STA knows whether it had done a L2/L3 roaming?

Only way it can know is if it tries to renew the IP and gets a NACK from
server, then it things subnet is changed (from NACK) and tries to do
a full DHCP handshake.