From: William Chen (kwchen@netvigator.com)
Date: Thu Nov 27 2003 - 13:37:06 GMT-3
Hi Paul,
Yes, you are right.
How about "switchport voice vlan untagged", I think it is also using the
same VLAN as data traffic.
- William Chen
----- Original Message -----
From: "Pun, Alec CL" <Alec.CL.Pun@pccw.com>
To: "William Chen" <kwchen@netvigator.com>;
<Ken.Farrington@barclayscapital.com>
Cc: <ccielab@groupstudy.com>
Sent: Friday, November 28, 2003 12:09 AM
Subject: RE: Voice VLAN (oh no, not again......)
> Just a minor advice :
>
> If dot1p is used, that implies voice traffic is using the same VLAN as
data
> traffic.
>
> regards,
> alec
>
> -----Original Message-----
> From: William Chen [mailto:kwchen@netvigator.com]
> Sent: Thursday, November 27, 2003 11:39 PM
> To: Ken.Farrington@barclayscapital.com
> Cc: ccielab@groupstudy.com
> Subject: Re: Voice VLAN (oh no, not again......)
>
>
> Hi Ken,
>
> See Below.
>
> ----- Original Message -----
> From: <Ken.Farrington@barclayscapital.com>
> To: <ccielab@groupstudy.com>
> Sent: Thursday, November 27, 2003 8:29 PM
> Subject: Voice VLAN (oh no, not again......)
>
>
> > Guys, At the risk of repeating questions on this forum, (I did read
some
> of
> > them) could someone just check out my comments/questions:-
> >
> > IP Phone (voice) configuration on c3550.
> > ----------------------------------------------------------
> >
> > The first thing to remember is that you always configure the following
two
> > commands:-
> >
> > From the Cisco config guide :-
> > 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.
> >
> >
> > Config 1 (trunked)
> >
> > mls qos
> > !
> > interface FastEthernet0/2
> > switchport access vlan 500
> > switchport trunk encapsulation dot1q
> > switchport trunk native vlan 500
> > switchport mode trunk
> > switchport voice vlan 501
> > switchport qos trust cos
> > no ip address
> > spanning-tree portfast
> > !
> >
> > Config 2 (non-trunked)
> >
> > mls qos
> > !
> > interface FastEthernet0/2
> > switchport access vlan 500
> > switchport mode access
> > switchport voice vlan 501
> > switchport qos trust cos
> > no ip address
> > spanning-tree portfast
> > !
> >
>
> First you don't have to set up trunk at the access port, the trunk
will
> be automatically setup run CDP between the cisco switch and the Cisco IP
> Phone (Don't know if you connect different IP phone with Cisco switch).
This
> special trunk is created and only allow the Voice VLAN and the access
VLAN.
>
> The packets from PC is untagged as normally, but the packets from the
IP
> phone can be either tagged or untagged. If the packets from the IP Phone
is
> untagged ("switchport voice vlan none", which is the default), it is
unable
> to distinguish the packets from those sent by the PC and therefore poor in
> QoS. The packets from the IP phone can also be tagged (a special trunk
will
> be formed in this case) in three different ways,
>
> 1. "switchport voice vlan <id>". This is the most common setting, the
IP
> phone is asked by CDP to send the packets tagged by the VLAN <id> to
> distinguish from PC packets.
> 2. "switchport voice vlan dot1p (NOT dot1q). This is a tagged packets
> with VLAN ID = 0.
> 3. "switchport voice vlan untagged". Although it is stated as
untagged,
> the packets is actually tagged with VLAN ID = 1025".
>
> In case 2 or 3, I think the switch will just accept it even it is a
> non-trunking port. It is because the packets is tagged with special VLAN
ID.
> (I would like to be confirmed if anyone know there is a document taking
> about it.)
>
> >
> > Questions
> >
> > What is the difference between these commands
> > switchport voice vlan 501
> > or
> > switchport voice vlan dot1q
>
> "switchport voice vlan 501" states the IP Phone packets should be
tagged
> with VLAN ID=501 and "switchport voice vlan dot1p (NOT dot1q) states the
IP
> Phone packets should be tagged with VLAN ID=0. Packets tagged with VLAN
ID=0
> is treated as the native VLAN's packets.
>
> Best Regards,
> William Chen
>
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