The port priority command sets the priority of an interface, that is, specifies the default priority of incoming packets on the interface. The device places packets in different queues based on priorities. By default, an interface on the device does not trust packet priorities, and packets enter queues based on the interface priority.

If all packets on an interface enter queues based on the interface priority, all packets enter the same queue. As a result, differentiated services cannot be provided. You can run the trust command to configure the device to perform priority mapping for packets based on the priority carried by the packets. That is, the device searches the priority mapping table based on the priority. Then, the device places packets in different interface queues based on the mapped priority and provides services for packets with different priorities through queue scheduling.