From: Scott Morris (smorris@ipexpert.com)
Date: Mon Jun 25 2007 - 09:57:05 ART
If there is no dot1q tag, there is no dot1p priority field!
Scott Morris, CCIE4 (R&S/ISP-Dial/Security/Service Provider) #4713, JNCIE
#153, CISSP, et al.
CCSI/JNCI-M/JNCI-J
VP - Technical Training - IPexpert, Inc.
IPexpert Sr. Technical Instructor
A Cisco Learning Partner - We Accept Learning Credits!
smorris@ipexpert.com
Telephone: +1.810.326.1444
Fax: +1.810.454.0130
http://www.ipexpert.com
_____
From: M S [mailto:michaelgstout@hotmail.com]
Sent: Monday, June 25, 2007 12:08 AM
To: smorris@ipexpert.com; acewer64@gmail.com; ccielab@groupstudy.com
Subject: RE: Voice Vlan 0 - DOT1P
I was looking at this today. Can you let me know if i have it backwards?
The 802.1p tag contains vlan 0, which is the native vlan. but when you
connect the cisco phone to the cisco switch a trunk is automatically formed.
With switchport interface command switchport access vlan 5, wouldn't the
data traffic be tagged with vlan 5 and the 802.1p traffic be placed into the
native vlan (vlan0)?
THank You.
_____
From: "Scott Morris" <smorris@ipexpert.com>
Reply-To: "Scott Morris" <smorris@ipexpert.com>
To: "'Alan Ewer'" <acewer64@gmail.com>, "'Cisco certification'"
<ccielab@groupstudy.com>
Subject: RE: Voice Vlan 0 - DOT1P
Date: Sun, 24 Jun 2007 21:59:21 -0400
If you search Cisco's website (or Google) you'll find lots of references for
VLAN 0 in regards to Voice VLANs. Basically, this is a designation for
untagged frames, which means whatever your trunk's native VLAN is set to in
the dot1q trunk to an IP phone, that's what VLAN 0 represents.
That'll also mean it's the same VLAN as your PC's data behind the phone, and
I'll tell you that's generally not a good idea in deployments. But this is
all about the lab. :)
So how about changing your voice vlan to something other than the default
command set!
To an IP phone, you SHOULD be trunking. The general spec is voice is tagged
(dot1q), PC data is untagged (access vlan AKA your trunk's native vlan,
untagged).
HTH,
Scott Morris, CCIE4 (R&S/ISP-Dial/Security/Service Provider) #4713, JNCIE
#153, CISSP, et al.
CCSI/JNCI-M/JNCI-J
VP - Technical Training - IPexpert, Inc.
IPexpert Sr. Technical Instructor
A Cisco Learning Partner - We Accept Learning Credits!
Telephone: +1.810.326.1444
Fax: +1.810.454.0130
http://www.ipexpert.com
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of Alan
Ewer
Sent: Sunday, June 24, 2007 8:36 PM
To: Cisco certification
Subject: Voice Vlan 0 - DOT1P
Hi all...
sorry if this has been answered before.....
I am playing around with voice vlans on 3550's
When I invoke the "switch voice vlan dot1p" command I get a message
referring to the voice VLAN being VLAN0, yet i cannot create/see VLAN 0
So where is this mystical VLAN ? How do I use it and why is the voice
traffic there ?? I would have thought that i would put it on the default
native vlan for the interface (usually vlan 1) .....as usual the Cisco doco
is unhelpful..and to some extent confusing (to me at least)...
Also if voice vlan is 0 and access vlan is 1, doesnt this imply that the
port is also trunking ??
any explanation gratefully accepted..
Regds
AlanE
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