Go CCIE Go!! - A Cisco Certified Internetwork Expert

In short, no. CoS fields are on tagged/trunked frames. Namely that coming from the phone itself. ...

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). ...