Voice VLAN

In this article we will discuss Voice VLAN, a brief discussion of Voice VLAN and the last article we will discuss about analog modems.



Voice VLAN is an ingenious feature that allows access ports to transmit voice traffic from an IP phone. Cisco IP phones connect to an IP network via Ethernet to send VoIP (Voice over Internet Protocol) packets.


The VLAN audio function is disabled by default. When the voice VLAN is enabled, all unmarked traffic is sent based on the priority of the default CoS port. The CoS value is not reliable for IEEE 802.1p or IEEE 802.1Q traffic.

The voice VLAN allows access ports to carry voice IP traffic from an IP phone. Port 1 connects to the key or any other VoIP device. Port 2 is an internal 10/100 interface that contains IP phone traffic. IP phones usually sit next to the computer on the same desk. They require the same UTP cables as computers and also use Ethernet. If we want to connect it to an adapter, we have two options.

Voice VLAN is supported only on access ports. The voice VLAN allows the adapter to accept the traffic marked on an access connector (usually not highlighted). CDP is used to negotiate a voice VLAN between the phone and the network switch (the adapter refers to the phone; this voice VLAN is a separate TLV in the CDP standard).
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