From: Diment, Andrew (adiment@qwest.com)
Date: Wed Feb 26 2003 - 14:46:18 GMT-3
I'm wondering if some of the confusion is coming from if there is a PC
hanging of the IP phone or not. The snip below came from a 3550 tutorial (I
hope it's not all over the page) that I believe came from iexpert.com. The
configs don't really explain what is going on but it says "the IP phone
configures a trunk". But the second config example says 'if you don't want
to trunk use 802.1p', but is there still a PC hanging off the phone????
Voice VLANs are VLANs that are for the sole purpose of carrying Voice over
IP traffic.
They are their own broadcast domain, and the switch can perform QoS on both
Voice
traffic and the other IP traffic coming into the port. In typical Voice VLAN
configuration
you plug your PC into the Cisco 7960 IP phone, and then plug your phone into
a
switchport. The IP Phone configures a trunk to the switch and sends the
Voice traffic
tagged with both an 802.1q header and a priority of 5, or 802.1q header with
a priority of
5. The IP traffic that is forwarded from the PC goes to the switch untagged
or on the
!0native VLAN!1
Example config with 802.1q
Switch(config)# mls qos
Switch(config)# interface interface-id
Switch(config-if)# mls qos trust cos
Switch(config-if)# switchport voice vlan vlan-id
If you don!/t want to trunk, you can do the same thing with 802.1p
Switch(config)# mls qos
Switch(config)# interface interface-id
Switch(config-if)# mls qos trust cos
Switch(config-if)# switchport voice vlan dot1p
-----Original Message-----
From: Frank Maisano [mailto:FrankM@netarch.com]
Sent: Wednesday, February 26, 2003 7:35 AM
To: 'XiangQu '; 'Hunt Lee '; 'ccielab@groupstudy.com '
Subject: RE: ??: RE: voice vlans correct configuration
The use of the trunk mode is an older way of configuring Voice vlans on the
3524 or 3548 switches. The 3550 supports the newer way without using trunk.
The real answer on the test may be in the wording of the question or as
indicated below, another command on the same port that would impose some
limits on your choices. If there are no other restrictions, I would go with
the non-trunk mode since it is the newer way that came along with the
3550's.
-FM
-----Original Message-----
From: XiangQu
To: Hunt Lee; ccielab@groupstudy.com
Sent: 2/26/2003 2:36 AM
Subject: Re: ??: RE: voice vlans correct configuration
At 14:21 2003-2-26 +0800, zhaozx@DigitalChina.com wrote:
>mls qos
>!
>interface fastethernet 0/10
>switchport mode trunk
>awitchport trunk native vlan 10
>switchport trunk encapsulation dot1q
>switchport voice vlan 100
>mls qos trust cos
>
>
>the 2nd one...
>
>Voice VLAN only works on a Trunk port ;-)
3550 document says Voice Vlan Port can also be a " Protected port " ,
this
implies voice vlan port can be an Access Port, since you can not
configure
a port as Trunk port & Protected port simultaneously.
So, Both configurations are correct !
http://www.cisco.com/univercd/cc/td/doc/product/lan/c3550/12112cea/3550s
cg/swvoip.htm
QuXJ
>Regards,
>Hunt
>
>
>-----Original Message-----
>From: Cezar Fistik [mailto:cfistik@moldovacc.md]
>Sent: Wednesday, 26 February 2003 12:57 PM
>To: ccielab@groupstudy.com
>Subject: voice vlans correct configuration
>
>
>Hi group,
>
>Could you please, share your ideas about the following configurations.
Just
>assume that an ip phone is connected to int fast 0/10 and to the phone
is
>connected a pc that is supposed to be in vlan 10
>
>1.
>mls qos
>!
>interface fastethernet 0/10
>switchport mode access
>switchport access vlan 10
>switchport voice vlan 100
>mls qos trust cos
>
>2.
>mls qos
>!
>interface fastethernet 0/10
>switchport mode trunk
>switchport trunk encapsulation dot1q
>switchport voice vlan 100
>mls qos trust cos
>
>Which one do you think is correct? Or if they are both incorect I'll
>appreciate any advice.
>
>Thanks,
>Cezar Fistik
Xiangjun Qu
_____________________________________________
Network Consulting Engineer CCIE#10593 (R&S)
Advanced Service, Cisco Systems (China).
Tel : (8610) 6526 7777 ext.5180
Mobile:(86) 13801211205
E-mail: xiangqu@cisco.com
_____________________________________________
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