So..., Alan suggested using unlang. I am actually reading un-language (5). If I use it, where or what file do I put your script in? =============================Script that Alan wrote==================================== authorise { if("%{User-Name}" =~ /[0-9a-z]{12}/i && "%{Huntgroup-Name}" == "MAB-switches"){ update control { Auth-Type := MAB } ok = return } } authenticate { Auth-Type MAB { ok } } ======================================================================== ================ I do understand that I need to revise it to make it only authenticate the right MAC addresses and only respond if the request meets certain criteria or have certain attributes. Can I include these logics in unlang such as User-Name == Calling-Station-Id or Service-Type == Call-Check? In addition, I want to assign these devices to a specific VLAN. Can I add the attributes here as well? Is this vlan assignment part of authentication or authorization? Alexander, I did read the links you gave me very carefully and I guess I understand the logic... However it seems that I have to edit many files. I am new to the FreeRadius and I don't have any programming experience... Is there a document which can tell me briefly what these files are for and how FreeRadius is using them? I don't really want to edit those files when I don't know enough about them... Thank you both for your advice! Difan