accessing diferent devices

Hi, I just installed the fre radius in a linux box. I got it working ok, but there is a couple of thig that i don´t know how to do or if they can be done. The first one is i need to create special kind of groups of people that can access some devices but no others, like i have the admin group that has to access all of the 20 devices (switches, routers..) but i also have the operator group that only has to access 2 of them, and on the same radius i need to enable some VPN users that only need to registrate to the radius for the VPN account that connects to the PX firewall and not to any of the devices... Can that be done?, how can i specify witch equipments the users have access to? Thanks. Carlos Reyes