Which of the following descriptions about MUX VLAN is wrong?
A . Each GROUP VLAN must be bound to a RINCIPAL VLAN
B . If the VLAN ID has been used for the PRINCIPAL VLAN, then the VLAN can no longer be used for the VLANIF interface, SUPER VLAN, and SUB VLAN
C . After the port is enabled with the MUX VLAN function, it can also be used for VLAN MAPPING and VLAN STACKING configuration
D . Enterprises can use PRINCIPAL PORT to connect to the corporate server, SEPARATE PORT to connect to corporate customers, and GROUP PORT to connect to corporate employees, so that can achieve the purpose of corporate customers and employees accessing the corporate server, while corporate employees can communicate with each other, but not between corporate customers, the corporate customers and corporate employees cannot access to each other.