Configuring a voice VLAN

Overview

The voice technology is developing quickly, and more and more voice devices are in use. In broadband communities, data traffic and voice traffic are usually transmitted in the network at the same time. Usually, voice traffic needs higher priority than data traffic to reduce the transmission delay and packet loss ratio.

A voice VLAN is configured for voice traffic. After assigning the ports that connect to voice devices to a voice VLAN, the system automatically modifies quality of service (QoS) parameters for voice traffic, to improve the transmission priority of voice traffic and ensure voice quality.

NOTE:

Common voice devices include IP phones and integrated access devices (IADs). Only IP phones are used in the voice VLAN configuration examples in this document.

OUI addresses

A device determines whether an incoming packet is a voice packet by checking its source MAC address. If the source MAC address of a received packet matches an organizationally unique identifier (OUI) in the voice device OUI list (referred to as the OUI list in this document) maintained by the switch, the packet is regarded as a voice packet.

You can add OUI addresses to the OUI list maintained by the device or use the default OUI list shown in Table 45 for voice traffic identification.

Table 45 The default OUI list

Number

OUI Address

Vendor

1

0003-6b00-0000

Cisco phone

 

 

 

2

00e0-7500-0000

Polycom phone

 

 

 

An OUI address is usually the first 24 bits of a MAC address (in binary format). It is a globally unique identifier assigned to a vendor by the IEEE. In this document, however, OUI addresses are used by the system to determine whether received packets are voice packets and they are the results of the AND operation of a MAC address and a mask. For more information, see "Adding OUI addresses to the OUI list."

You can remove default OUI addresses and if needed, add them to the OUI list after their removal.

Voice VLAN assignment modes

A port connected to a voice device, an IP phone for example, can be assigned to a voice VLAN in one of the following modes:

•Automatic mode—The system matches the source MAC addresses in the protocol packets (tagged packets) sent by the IP phone upon its power-on against the OUI list. If a match is found, the system

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