From: Avner Izhar (aizhar@ccbootcamp.com)
Date: Mon Jun 25 2007 - 12:12:07 ART
The behavior will be a bit different from what you describe ...
Think of the dot1p command as a way to allow QoS while the voice and the data
are in the same vlan,
and think of old XL series switches that don't know how to read DSCP values.
The command instructs the phone to mark all voice traffic with an 802.1q tag,
but the vlan part of the
tag will always be 0 (zero) and the Cos part will be 5, add some trust
commands and you end up with a port
that incoming voice and data traffic on it are on the same vlan, but with
different QoS treatment.
When a switch receive an 802.1q tag with vlan = 0, it places it in to the
native vlan.
That way of configuring things is pretty much outdated now days, since voice
and data should_not be on the
same vlan. So the common way is to enable the auxiliary vlan support on a
port which allow a non-tagging
port to understand and forward tagged traffic from one single vlan (the voice
vlan).
What are you trying to configure, if you will explain your needs, perhaps I'd
be able to suggest an alternate config ...
-------------------------------------------
Regards,
Avner Izhar
Technical Instructor
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________________________________
From: nobody@groupstudy.com on behalf of Alan Ewer
Sent: Mon 6/25/2007 12:20 AM
To: M S
Cc: smorris@ipexpert.com; ccielab@groupstudy.com
Subject: Re: Voice Vlan 0 - DOT1P
Hi ..
My understanding (as feeble as it is ) is as follows:
If the fport is considered as such:
int fas 0/10
switch access vlan 10
switch voice vlan dot1p
Then the voice traffic will come end up on vlan 1 (default native vlan for
trunk) and untagged data from pc will end up as vlan 10
if the config is as follows:
int fas 0/10
switch access vlan 10
switch voice vlan dot1p
switch trunk native vlan 200
then the untagged data will end up as vlan 10 and the voice as 200 (because
it is the native vlan)
Is this correct ?
Regds
Alan E
On 6/25/07, M S <michaelgstout@hotmail.com> wrote:
>
> 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!
>
> smorris@ipexpert.com
>
> Telephone: +1.810.326.1444
> Fax: +1.810.454.0130
> http://www.ipexpert.com <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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