3Com 3CBLSG48 User Guide - Page 172

Defining Voice VLAN CHAPTER 13: CONFIGURING QUALITY OF SERVICE 161 Voice VLAN allows network administrators to enhance the 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: Viewing Voice VLANs Defining Voice VLAN Defining Voice VLAN Port Settings Viewing Voice VLAN Port Definitions Viewing the OUI Summaries Modifying OUI Definitions