..::Cisco Nac::..

Hi everyone, I need to configure a freeradius server to grant access to our Network based in the Cisco Nac solution. I just want to know if anyone has configured Cisco Nac on their network and any advice when doing it. Right know we are just gathering all the information related (Vendor specific attributes), and the other question is how can we prevent the system users to authenticate on the radius?. Thanks in advance. regards. Alfonso.