FR and AD with ntlm and Users group

Hi, I am authenticating my Cisco devices by integrating FreeRadius with Active Directory. Not using LDAP but ntlm_auth. Now If I make a group on my AD server for example Router Admins and put some users in it. Now, where would I define in the FreeRadius that only users from Router Admin group are permitted. Do I need to define it in the smb.conf? BR, Raheel