Configuring Voice VLANs

Voice VLAN Configuration Guidelines

•In untrusted mode, all traffic in IEEE 802.1Q or IEEE 802.1p frames received through the access port on the Cisco IP Phone receive a configured Layer 2 CoS value. The default Layer 2 CoS value is 0. Untrusted mode is the default.

Note Untagged traffic from the device attached to the Cisco IP Phone passes through the phone unchanged, regardless of the trust state of the access port on the phone.

Related Topics

Configuring the Priority of Incoming Data Frames, on page 155

Example: Configuring a Port Connected to an IP Phone Not to Change Frame Priority, on page 158

Voice VLAN Configuration Guidelines

•Because a Cisco 7960 IP Phone also supports a connection to a PC or other device, a port connecting the switch to a Cisco IP Phone can carry mixed traffic. You can configure a port to decide how the Cisco IP Phone carries voice traffic and data traffic.

•The voice VLAN should be present and active on the switch for the IP phone to correctly communicate on the voice VLAN. Use the show vlan privileged EXEC command to see if the VLAN is present (listed in the display). If the VLAN is not listed, create the voice VLAN.

•The Power over Ethernet (PoE) switches are capable of automatically providing power to Cisco pre-standard and IEEE 802.3af-compliant powered devices if they are not being powered by an AC power source.

•Before you enable voice VLAN, we recommend that you enable QoS on the switch by entering the mls qos global configuration command and configure the port trust state to trust by entering the mls qos trust cos interface configuration command. If you use the auto-QoS feature, these settings are automatically configured.

•You must enable CDP on the switch port connected to the Cisco IP Phone to send the configuration to the phone. (CDP is globally enabled by default on all switch interfaces.).

•The Port Fast feature is automatically enabled when voice VLAN is configured. When you disable voice VLAN, the Port Fast feature is not automatically disabled.

•If the Cisco IP Phone and a device attached to the phone are in the same VLAN, they must be in the same IP subnet. These conditions indicate that they are in the same VLAN:

◦They both use IEEE 802.1p or untagged frames.

◦The Cisco IP Phone uses IEEE 802.1p frames, and the device uses untagged frames.

◦The Cisco IP Phone uses untagged frames, and the device uses IEEE 802.1p frames.

◦The Cisco IP Phone uses IEEE 802.1Q frames, and the voice VLAN is the same as the access VLAN.

•The Cisco IP Phone and a device attached to the phone cannot communicate if they are in the same VLAN and subnet but use different frame types because traffic in the same subnet is not routed (routing would eliminate the frame type difference).

 

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Cisco Systems WSC2960XR48FPSI manual Voice Vlan Configuration Guidelines
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WSC2960XR48FPSI specifications

The Cisco WSC2960XR48FPSI is an advanced, high-performance switch that plays a vital role in today's enterprise networking environments. Designed for reliability and efficiency, it serves as a foundational component for organizations concentrating on network agility and scalability.

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