We are using IP address to differentiate two groups of users who exist in the same LAN. The IP addresses are assigned by MT Hotspot. Currently when user turn on their PC, they are assigned an IP by MT DHCP. When they log in using Hotspot, our Radius server will assign an IP from the Framed_pool IP addresses which the user belong to (according to username). This is where the problem arise, the address assigned by MT after the user login to the hotspot does not correspond to the address assigned by DHCP. MT will just do address mapping between the user MAC and the radius-assigned IP.

That's fine for normal web surfing. However, we found that this creates a problem with MSN Messenger. Also recently we found that some users are getting login page every 20min, they will have to re-login everytime they see the login page in order to continue. After we statically set the IP address to be the same as that of MT Radius-assigned IP, the problem went away.

Does anyone know how to get MT-DHCP to re-assign IP address to be the same as the address assigned by Radius?