FreeRADIUS VLAN Attributes per Certificate, not user.

Greeting all! With the "users" file you can add three attributes that the RADIUS server passes to a switch and the switch dynamically assigns a VLAN to the port. However, can this be done when the client is authenticated via a certificate? Where can I specify these three attributes for the ceritifcate? I'm on FreeRADIUS 2.1.x (x is most probably 3)