We have an application were we provide voice over IP services to a customer with a centralized Call Manager. We want the PC's of the customer to be connected to IP phones and we want to have a different VLAN for the phones and the PC's. One of our concern is that we don't want the customer to access the voice VLAN. Is there a security issue here, if the customer use a PC equipped with a 802.1Q network card and by any chance he knows the voice VLAN ID, can he access the VLAN dedicated to voice and by the same time have access to the Call Manager, or any other servers on the same VLAN??