Just to add on.
I have got the Radius authentication working for wireless users.
Wireless users — existing AP (configured with WPA and point to the ZeroShell desktop as the radius server) — > Internet .
Wireless users are getting a login prompt when they select the HotSpot SSID to connect. However, I would want a web login page to prompt instead, and this would need the Captive Portal mode. any adivse how to proceed from here ?