Voice vlan / auxillary vlan

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Dec 17th, 2007
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What are the advantages/disadvantages to using the voice vlan configuration versus two normal vlans when configuring VoIP? I am just trying to understand why you wouldn't just create a second vlan for voice and then trunk it.

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ccbootcamp Mon, 12/17/2007 - 19:04
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How would the phone automatically know which VLAN to use for voice traffic?




(please rate the post if this helps!)

a.cruea1980 Thu, 01/03/2008 - 07:32
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Well, for one, you can't really assign two VLANs to the same port and have them be "normal" VLANs. Yeah, you can trunk it, but then you have a primary VLAN and a native VLAN, and all untagged traffic flows over your native VLAN. While you can QoS that, you can't guarantee that it's only carrying phone traffic.

Using the native VLAN for traffic is kind of insecure; a rogue device can be put on a port that's not in any VLAN, and guess what it sends data over? Native VLAN, generally.

That's all I can really think of as to why you don't want your phone or data flowing over your native VLAN.

The biggest advantages to using the aux/voice vlan are segregating your voice traffic from data, and then being able to do QoS on that traffic and knowing what should be going where.


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