Force DHCP disconnecting large number of clients with valid IP addresses

[kyle_connor]

Hello,

I have a vSZ with 180 APs split across 2 zones and multiple subnets with 600 - 1000 clients. I am utilizing R700 APs. I have an issue where clients were sticking with an IP address of one subnet after successfully roaming from one building's subnet to another. I looked around and found the Force DHCP option which looked like it did the trick, however I am getting A LOT of Force DHCP disconnection events.

I can confirm the Force DHCP option did handle the clients that were stuck on the wrong subnet, but there appears to be a lot of clients that have valid IP addresses on the correct subnet that are also getting kicked off.

I am using external DPSK authentication for this network. I've also had a couple people with multiple devices which were able to join the network on 4 of 5 devices and the other just lagged and then refused to connect. I confirmed the 5th device was getting kicked due to the Force DHCP option. I had the person connect to an alternative WLAN with same authentication but no Force DHCP option enabled and it connected fine.

Does anyone have some insight as to how the SmartZone or APs apply this option? A few things that are not immediately clear are:

1) How does the SmartZone judge if a device got a valid DHCP address?

2) What occurs that causes the SmartZone (or AP?) to start the timeout counter for getting a valid DHCP address? 

Otherwise, any other suggestions on how to either fix this Force DHCP issue or to get rid of my "sticky client to a subnet" issue would be very appreciated. 

Thanks!