RE: Trust VoIP and remark Data

From: Scott Morris (smorris@ipexpert.com)
Date: Thu Dec 13 2007 - 15:09:30 ART


That would depend on what your lab's expectations are. If you are told how
your phone will send things (cos 5 and dscp 46) and led down the path of mls
qos and then router-based MQC policies are created using DSCP EF (46)
values, I would suggest changing the cos-dscp map as well. If the proctors
did not already know this little background tidbit (which I expect they did)
then they certainly do now! :)
 
You cannot go wrong by changing the cos-dscp map.
 
HTH,
 

Scott Morris, CCIE4 (R&S/ISP-Dial/Security/Service Provider) #4713, JNCIE-M
#153, JNCIS-ER, CISSP, et al.
CCSI/JNCI-M/JNCI-ER
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: nhatphuc [mailto:nhatphuc@gmail.com]
Sent: Thursday, December 13, 2007 1:06 PM
To: smorris@ipexpert.com
Cc: Darren Johnson; Cisco certification
Subject: Re: Trust VoIP and remark Data

Should i adjust cos-dscp map in lab exam or just in real world?

Thank you for your reply

Phuc

On Dec 13, 2007 7:39 PM, Scott Morris <smorris@ipexpert.com
<mailto:smorris@ipexpert.com> > wrote:

I'd also adjust your mls qos cos-dscp map then. The default will read cos 5

and remap the dscp to 40 instead of 46.

:)

Scott Morris, CCIE4 (R&S/ISP-Dial/Security/Service Provider) #4713, JNCIE-M
#153, JNCIS-ER, CISSP, et al.
CCSI/JNCI-M/JNCI-ER
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

-----Original Message-----
From: nobody@groupstudy.com <mailto:nobody@groupstudy.com>
[mailto:nobody@groupstudy.com] On Behalf Of

Darren Johnson
Sent: Thursday, December 13, 2007 6:46 AM
To: 'nhatphuc'; 'Cisco certification'
Subject: RE: Trust VoIP and remark Data

Hey there! I believe your second option is wrong, you don't need the
override and you need to trust cos. I would do it like this....

mls qos trust device cisco-phone
mls qos trust cos
mls qos cos 1

This says trust the COS value ONLY if a Cisco phone is detected via CDP, and
any packets/frames without a COS value (such as those received from a PC on
the native vlan) use a COS value of 1. The COS override would 'override' any

COS values to 1, including COS values received from the phone!! I don't
believe you want to do this!

Dazzler

-----Original Message-----
From: nobody@groupstudy.com <mailto:nobody@groupstudy.com>
[mailto:nobody@groupstudy.com] On Behalf Of
nhatphuc
Sent: 12 December 2007 17:55
To: Cisco certification
Subject: Trust VoIP and remark Data

Hi Group,

With question: Ensure that VoIP traffic originating from the IP phones
maintains its CoS value, while traffic originating from the PCs is remarked
with a CoS of 1

I see 2 ways to answer. The first seems to be better, but I don't see
anything wrong with the second. Which one do you choose? Please explain.

mls qos trust cos
switchport priority extend cos 1

and
mls qos trust device cisco-phone
mls qos cos 1 override

Thank you

Phuc



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