From: nhatphuc (nhatphuc@gmail.com)
Date: Thu Dec 13 2007 - 23:22:23 ART
Darren and all,
I understand your explain about "override".
Regarding option 1:
mls qos trust cos
switchport priority extend cos 1
Do we need to add "mls qos trust device cisco-phone"? or "switchport
priority extend cos 1" implies cisco-phone? Without "mls qos trust device
cisco-phone" and PC directly connected to switch, will the switch trust PC
frames with CoS preset?
Without "mls qos trust device cisco-phone", show mls qos interface says:
Trust device:none
Regarding Option 3:
mls qos trust device cisco-phone
switchport priority extend cos 1
According to this link:
http://www.cisco.com/univercd/cc/td/doc/product/lan/cat3560/12240se/scg/swqos
.htm#wp1229179
To configure trust boundary, we use:
mls qos trust cos | dscp
mls qos trust device cisco-phone
So "mls qos trust device cisco-phone" never stands alone because the switch
doesn't know what to trust (cos or dscp). Is this correct?
It seems that the best answer is combine Option 1 and 3?
Phuc
On Dec 14, 2007 1:39 AM, Darren Johnson <dazza_johnson@yahoo.co.uk> wrote:
> Good evening all, and good questions Phuc!
>
>
>
> See my responses below:
>
>
>
> *From:* nhatphuc [mailto:nhatphuc@gmail.com]
> *Sent:* 13 December 2007 18:24
> *To:* Darren Johnson
> *Cc:* Cisco certification
> *Subject:* Re: Trust VoIP and remark Data
>
>
>
> Hi Darren and all,
>
> I used "override" because without it, switch only remarks untagged frame,
> and leaves other frame intact. I use this together with "mls qos trust
> device cisco-phone" because I think trust device have higher priority than
> "mls qos cos 1 override". Am I correct?
>
> Not sure if override has a 'lower priority' than 'mls qos trust device
> Cisco-phone' but I cannot see what you are achieving here. I thought your
> post wanted to trust COS from phone and from PC (untagged) set COS to 1
> override is uneccsary in this instance.
>
>
>
> About your configuration, can we "trust device" and "trust cos" together?
> I haven't tried yet
>
> Yes. You tell the switch to either trust COS or DSCP. The switch will then
> trust these values no matter what. If you add 'mls qos trust device
> Cisco-phone', the trust of the COS or DSCP command configured previously,
> will only apply if a Cisco phone is detected. Therefore:
>
> Option 1
>
> Mls qos trust dscp --` Trusts dscp irrecspective of device attached
>
> Option 2
>
> Mls qost trust dscp
>
> Mls qos trust device Cisco-phone --` trust DSCP only if Cisco phone is
> connected
>
>
>
> After reading all of your answers and thinking again. I have a third
> option. I repost all 3:
>
> option 1:
> mls qos trust cos
> switchport priority extend cos 1
>
> option 2:
> mls qos trust device cisco-phone
> mls qos cos 1 override
>
> option 3 :
> mls qos trust device cisco-phone
> switchport priority extend cos 1
>
>
>
> In my opinion:
>
> Option 1 would work
>
> Option 2 would NOT work
>
> Option 3 would work, not sure if you need to add 'mls qos trust cos'
> though
>
>
>
> In fact, I took the first option from IEWB. I used to choose that, but now
> I think why don't we choose the 3rd one? Isn't it better than the 1st?
>
> Thank you
>
> Phuc
>
> On Dec 13, 2007 6:45 PM, Darren Johnson <dazza_johnson@yahoo.co.uk>
> wrote:
>
> 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] 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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