show mls qos fastethernet 0/1"

[sarahr202]

Hi everybody

"show mls qos fastethernet 0/1"

The above command Shows a number of parameters, one of them is " trust device" . " Trust device" is shown as  none, cisco-ip phone, trusted"

My book is very confusing as to what " trust device" indicate In " show mls qos int ' command

If we configure the command:

mls qos trust device cisco-phone, and Cisco ip phone is connected, what will " trust device" indicate?

If cisco phone is not connected but some other third party phone is connected what will " trust device" indicate?

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If we don't configure above command ,but configure :

switchport priority extend trust

what will " trust device " indicates?

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If we have configured both command:

mls qos trust device cisco-phone

switchport priority extend trust.

What will " trust device" indicate?

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Thanks and have a great weekend.

[Alessio Andreoli]

Hi Sarah,

essentially the question would be :

" Do you trust how that device you are going to connect mark the traffic?"

Cisco ip-phone is an option because there is full interoperability between the switch and a Cisco IP-phone. the book will laso tell you that it is a good practise to limit the "trust perimiter" to the switch itself. This means that whatever CoS value is getting in the switchport, if the trust perimeter is on the switch, the switch will re-mark the traffic how you will decide.

A very bad practice for example is to connect a PC to a switchport and to define that device as belonging to the trust area.

that PC can inject everything in the network and that is what you do not want.

Example, i wantto play the cool one and i run an application which will set CoS 5 to the data packet transporting my email.

Would you administrator be happy?

HTH

Alessio

[sarahr202]

thanks Alessio

My intention was to learn how to interpret the output of " show mls qos int f1/1" specifically the parameter "Trust device."

As i mentioned, the parameter" trust device" could be None, cisc-phone, or trusted.

I just wanted to know how different commands such as:

mls qos trust device cisco-phone

switchport priority extend trust.

determine what " trust device" parameter indicate?

Thanks and have a great weekend.