Force a new DHCP lease when roaming between vSZ APs

Question

Hi all,

Does anyone know of a way to force a client to pull a new DHCP lease every time they roam to a new AP? vSZ version 3.2

michael_brado · Answer

Lastly, a security aspect of the feature is it also disallows the use of Static IPs.

john_d · Answer

I think it will likely be helpful. Most clients don't consider roaming from BSSID to BSSID as grounds for re-checking gateway connectivity / requesting a new IP.

So, if this option is checked, AND a client roams with a sticky DHCP lease, the AP will kick out the client. This should cause the client to reassociate to the SSID at some later time and ask for a new DHCP lease.

eizens_putnins · Answer

For my understanding, this option will not make a big difference  in case of L3 roaming:
1. clients with incorrect static address don't have access to network anyway. 
2. If client sticks to previously received DHCP address, this option will not allow clients to connect to WLAN on a new AP bridged to different VLAN (as it is not requested new IP from DHCP server). But this client doesn't have access to WLAN anyway, as his IP is wrong for this VLAN.  
So nit has no much effect on this sticky clients. Otherwise ""Force DHCP" feature is very usefull - to avoid users playing with static IPs.
Sticking to old IP primarly become a problem for laptops or tablets which are put to sleep and moved to other building or site, where same SSID is bridget to different VLAN. You can't prevent problem  completely (it is actually problem of client and network design mainly), but you can make shorter DHCP lease time to limit damage.

Even better way is to use tunneled WLANs, when you need same SSID on different sites and with different IP addressing, and some users often move between this sites. Also you can use them in areas where L3 roaming really happens fast and often. Usually you prefer to avoid such situation from the very beginning, keeping this in mind when designing networks, and use VLAN pooling instead of L3 roaming feature in a big sites with intensive roaming, many users and APs.

Hope it helps.