1-4 
 
For more information about CoS and DSCP precedence values, refer to the QoS part of the manual.  
Configuring Voice VLAN Assignment Mode of a Port 
A port can work in automatic voice VLAN assignment mode or manual voice VLAN assignment mode. 
You can configure the voice VLAN assignment mode for a port according to data traffic passing through 
the port. 
Processing mode of untagged packets sent by IP voice devices 
z  Automatic voice VLAN assignment mode. An Switch 4200G Ethernet switch automatically adds a 
port connecting an IP voice device to the voice VLAN by learning the source MAC address in the 
untagged packet sent by the IP voice device when it is powered on. The voice VLAN uses the aging 
mechanism to maintain the number of ports in the voice VLAN. When the aging timer expires, the 
ports whose OUI addresses are not updated (that is, no voice traffic passes) will be removed from 
the voice VLAN. In voice VLAN assignment automatic mode, ports can not be added to or removed 
from a voice VLAN manually. 
z  Manual voice VLAN assignment mode: In this mode, you need to add a port to a voice VLAN or 
remove a port from a voice VLAN manually. 
Processing mode of tagged packets sent by IP voice devices 
Tagged packets from IP voice devices are forwarded based on their tagged VLAN IDs, whether the 
automatic or manual voice VLAN assignment mode is used.  
 
 
If the voice traffic transmitted by an IP voice device carries VLAN tags, and 802.1x authentication and 
guest VLAN is enabled on the port which the IP voice device is connected to, assign different VLAN IDs 
for the voice VLAN, the default VLAN of the port, and the 802.1x guest VLAN to ensure the effective 
operation of these functions. 
 
Support for Voice VLAN on Various Ports  
Voice VLAN packets can be forwarded by access ports, trunk ports, and hybrid ports. You can enable a 
trunk or hybrid port belonging to other VLANs to forward voice and service packets simultaneously by 
enabling the voice VLAN. 
For different types of IP phones, the support for voice VLAN varies with port types and port configuration. 
For IP phones capable of acquiring IP address and voice VLAN automatically, the support for voice 
VLAN is described in 
Table 1-2.