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Voice VLAN Explained: Basics, Configuration & FAQ

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Voice VLAN Explained: Basics, Configuration & FAQ

In IP-based Ethernet networks, the voice VLAN is vital to ensure voice quality. Then what is it? How does voice VLAN work? What can we benefit from this? Get all the answers to these questions and other frequently asked questions about voice VLAN from this post.

What is voice VLAN?

Voice VLAN (Voice VLAN) is a VLAN (virtual local area network) specially designed to carry client voice traffic. When configuring a Voice VLAN and including ports with VoIP equipment in this VLAN, the user gets the opportunity to configure the quality of service (QoS) parameters for voice data and increase the priority of voice traffic, thereby improving call quality.

Voice VLAN or voice VLAN is used to isolate voice traffic from data for two reasons:

1. Security. Software already exists, such as Wireshark and Voice Over Misconfigured Internet Telephones (VOMIT), that allow attackers to recognize and capture voice packets, and then process and convert them into audio files with a WAV extension like Business VoIP. To prevent this from happening, it is necessary to isolate voice traffic from other things.

2.QoS. Used to facilitate the prioritization of voice traffic, among other things.

How does voice VLAN work?

To prioritize voice streams, they must first be identified. The Voice VLAN can identify the voice data stream in two ways: one is by determining the source MAC address of the received packet (MAC address-based mode), and the other is by identifying the VLAN tag of the received packet (VLAN-based mode).

In the MAC address-based mode, the network switch can determine whether the data stream is a voice data stream according to the source MAC address field in the data packet arriving at its interface. As shown in the following figure, after the switch receives the data packet sent by the PC and the IP phone, it performs the following processing: if the source MAC address matches the OUI (organization unique identifier) ​​configured on the switch, the VLAN voice tag is added to the packet And increased the priority of the packet. If the source MAC address does not match the OUI, the VLAN PVID tag will be added to the packet and the packet will not be sent first.


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