QOS - Need clarification.

[pentagel]

Hello, What happen to the boundary when you have something like:

Interface xxx

Switchport access vlan xx

Switchport voice Vlan dot1p

Switchport priority extend cos 4

MLS QOS trust COS

Now, I am extending the priority to the IP phone (Rewrite cos to a value of 4) but at the end, I state that I want the QOS to be trusted....

Unless the MLS QOS TRUST COS is intended to act on the COS of the phone only? But then I would have to specify "MLS QOS TRUST device Cisco-phone" or it would be applied to all traffic (PC and phone)??

Thanks a lot for any clarification

[Brandon Buffin]

With this configuration, the "mls qos trust cos" command is essentially acting only on traffic from the phone as you have told the port to remark traffic coming from the device connected to the switchport on the phone to COS 4 with the "switchport priority extend cos 4" command. If you did not have the "switchport priority extend" command OR if another device such as a PC were plugged directly into the switchport, all COS values would be trusted. The "switchport priority extend" command only applies to traffic from the switchport on a phone.

Hope this helps. If so, please rate the post.

Brandon