3com 2924-PWR User Manual

C

HAPTER

 13: C

ONFIGURING

 Q

UALITY

 

OF

 S

ERVICE

Voice VLAN allows network administrators to enhance VoIP service by 
configuring ports to carry IP voice traffic from IP phones on a specific 
VLAN. VoIP traffic has a preconfigured OUI prefix in the source MAC 
address. Network Administrators can configure VLANs on which voice IP 
traffic is forwarded. Non-VoIP traffic is dropped from the Voice VLAN in 
auto Voice VLAN secure mode.

 

Voice VLAN also provides QoS to VoIP, 

ensuring that the quality of voice does not deteriorate if the IP traffic is 
received unevenly. The system supports one Voice VLAN. 

There are two operational modes for IP Phones: 

■

IP phones are configured with VLAN-mode as enabled, ensuring that 
tagged packets are used for all communications. 

■

If the IP phone’s VLAN-mode is disabled, the phone uses untagged 
packets. The phone uses untagged packets while retrieving the initial 
IP address through DHCP. The phone eventually use the Voice VLAN 
and start sending tagged packets. 

This section contains the following topics: 

■

■

■

■

■

■