Which two statements about voice VLANs are correct？（）

A.Voice VLANs eliminate the need for QoS configuration

B.Voice VLANs are used on trunk links to eliminate the need for QoS CoS markings

C.Voice VLANs are mainly used to reduce the number of access switch ports that are used in the network

D.Voice VLANs can be configured to forward existing CoS priorities or override them

E.Voice VLANs are mainly used between access layer switches and distribution layer switches

F.Voice VLANs can be configured on Layer 2 ports only