From: mani poopal (mani_ccie@yahoo.com)
Date: Tue Mar 22 2005 - 08:02:51 GMT-3
Hi Jongso/Matt,
Matt thanks for your explanation, I will go with default trunking mode for voice vlan configuration.
Unless they ask in the exam you don't need these commands, I will put mls qos and -if)mls qos trust cos. In addition to above commands, depending on the question I will use either of these commands.
A.-if)#switchport priority extend cos 3-------->Ask to overide the default cos value(which is set to zero by switch0
B-if)#switchport priority extend trust cos---->Ask to trust the cos value from PC's(default IP phone makes the cos to 0)[In this situaltion PC's cos defalt value 5 is preserved and not defalted to zero by ip phone's switch]
(A.)Overriding the CoS Priority of Incoming Data Frames
Step 3
switchport priority extend
cos value
Set the IP phone access port to override the priority received from the PC or the attached device.
The CoS value is a number from 0 to 7. Seven is the highest priority. The default is 0.
Use the no switchport priority extend interface configuration command or the switchport priority extend cos 0 interface configuration command to return the port to its default setting.
(B)Configuring the IP Phone to Trust the CoS Priority of Incoming Data Frames
Step 3
switchport priority extend trust
Set the IP phone access port to trust the priority received from the PC or the attached device.
Use the no switchport priority extend interface configuration command or the switchport priority extend cos 0 interface configuration command to return the port to its default setting.
http://www.cisco.com/univercd/cc/td/doc/product/lan/c3550/12225se/3550scg/swvoip.htm#wp1033944
Mani
Thanks for a good explanation Matt
I remember I used to struggle a lot on this.
I never thought about dynamic mode...
One question though " switchport priority trust cos" on Method1 is
necessary?
First, I can't find this command from CCO. I only see "switchport priority
extend ..."
But as far as I know, this command("switchport priority extend ...") advise
VoIP Phone on how to tag data traffic, which can also be used in method 2. I
am just trying be 100% sure as my lab date is coming soon ( 5 April)
Regards
Jongsoo
-----Original Message-----
From: Matt White [mailto:mwhite23@gmail.com]
Sent: Saturday, 19 March, 2005 11:16 PM
To: mani poopal
Cc: ccielab@groupstudy.com
Subject: Re: configurin VOICE VLAN.
For the 3550 and up, #1 is correct. #2 only needs to be used if you
have a 3500XL or below.
Keep in mind the switchport is dynamic by default, and will trunk
automatically, regardless of the voice VLAN.
Officially, #2 is wrong, as hardcoded trunks are not technically
supported on an interface. However you see it implemented fairly often
this way.
On Mar 19, 2005, at 10:54 PM, mani poopal wrote:
> Guys,
>
> If the question ask to configure voice vlan 200 and data vlan of 20,
> which method is wright. Any suggesions are appreciated.
>
> Method1:(DOC CD and IWEB method)
> mls qos
> int fa 0/10
> mls qos trust cos
> switchport access vlan 20
> switchport voice vlan 200
> switchport priority trust cos
>
> Method2:(CISCO PRESS CCIE LAB EXAM book method)
> mls qos
> int fa 0/10
> mls qos trust cos
> switchport access-vlan 20
> switchport voice-vlan 200
> switchport trunk encapsulation dot1q
> switchport moe trunk
> switchport native vlan 20
>
> So the question, if the voice vlan is asked to configure, which method
> is right.
>
> thanks in advance for the replies and reasoning.
>
> Mani
>
>
>
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