Control user logins by NAS

Hi all, How can I control what groups can authenticate on what nas. I would like to create a batch of users and assign those users to only sucessfully login from a particular nas (or list of nas's) I have freeradius 1.04 and use sql for the user/password combinations Group 30 mins Simultanious Use := 1 Idle Timeout = 600 Max All Sessions := 1800 It is a wireless hotspot setup. Do I need to use huntgroups or can I add an attribute to the group? Thanks in advance Shane