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What is a Voice VLAN in EX-series switches and how to configure it?

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Knowledge Base ID: KB11062
Last Updated: 31 Aug 2010
Version: 3.0

Summary:

EX-series switches accommodate implementation scenarios that include an IP phone and a user’s PC connected to a single switch port.  Typically administrators choose to treat VoIP traffic differently than user data traffic.  In order to do this a mechanism must be able to separate common user data traffic from voice traffic. The voice VLAN is used for this purpose. The voice VLAN enables a single access port to accept untagged, data traffic as well as tagged, voice traffic and associate each type of traffic with distinct and separate VLANs. By doing this, voice traffic can be treated differently, generally with a higher priority than common user data traffic. The following information shows how to configure and monitor Voice VLAN in EX-series switches.

Problem or Goal:
 

Solution:

 The Voice VLAN feature in EX-series switches enables access ports to accept both data (untagged) and voice (tagged) traffic and separate that traffic into different VLANs. 

  • Before configuring Voice VLAN, there are several things to consider:

    1. To assign differentiated priority to Voice traffic, it is recommended that class of service (CoS) is configured prior to enabling the voice VLAN feature. Typically, voice traffic is treated with a higher priority than common user traffic. Without differentiated treatment through CoS, all traffic, regardless of the type, is subject to the same delay during times of congestion.
    2. The voice VLAN should only be enabled on access ports on which IP phones are actually connected.
    3. Utilize Link Layer Discovery Protocol Media Endpoint Discovery (LLDP-MED) to provide the voice VLAN ID and 802.1p values to the attached IP phones. This dynamic method associates each IP phone with the appropriate voice VLAN and assigns the necessary 802.1p values, which are used by CoS, to differentiate service for voice traffic within a network.
  • Voice VLAN Configuration. In the configuration sample below  we define voice vlan  for interface ge-0/0/9 with vlan name voice. we also assign  forwarding class voice.

    [edit ethernet-switching-options]
    user@switch# show
    voip {
        interface ge-0/0/9 {
            vlan voice;
            forwarding-class voice;
        }
    interface ge-0/0/10 {
            vlan voice;
            forwarding-class voice;
    }
        } interface ge-0/0/11{
            vlan voice;
            forwarding-class voice;
        }
    }
  • Voice VLAN Monitoring
    To monitor voice VLAN, use the show vlans detail <vlan-name> command. This command shows voice VLAN details such as membership, tag, and state information.

    user@switch> show vlans detail voice
    vlan voice:
        Admin state :      Enabled
        Tagging     :      802.1Q Tag 500
        Description :      None
        Primary IP  :      None
        STP         :      None
        Tag         :      ge-0/0/9.0
                           ge-0/0/10.0*
                           ge-0/0/11.0                    * - Active
        Untag       :      None

Purpose:
Configuration

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