mls qos trust device cisco-phone =
Trust marking only from a cisco IP phone (The switch uses cdp to know a cisco phone is plugged into the port).
mls qos trust cos =
This command instructs the switchport to trust class of service (cos) markings originating from the device plugged into the port.
auto qos voip cisco-phone =
This command enables / starts auto qos on the switch port and tells the switch to place commands that trust markings only from a cisco phone.
Cisco devices use CDP (cisco discovery protocol) to detect each other. For non cisco devices you will have to configure how you want the trust to be established.
By default cisco IP phone will mark voice traffic as 5. So say for instane I want to mark a COS from a device you could say
mls qos trust cos
switchport priority extend cos 5
The second command will mark traffic from the phone with cos 5 which is recommended for voice traffic. There is more to COS. This is the tip of the iceberg.
Pls rate if helpful.
