Which are the two subfields in the port identifier of the uplink port on a non-root switch in RSTP?

The correct answer identifies the structure of the port identifier within the context of Rapid Spanning Tree Protocol (RSTP) on a non-root switch. In RSTP, the port identifier is essential for maintaining the topology of a network and ensuring effective path selection.

The port identifier is composed of two key components: a port priority and a port number. This combination allows switches to differentiate between multiple ports when determining the best path for data transmission. Specifically, the port priority is allocated 1 byte, offering a range of 0-255 for priority values, while the port number is also allocated 1 byte, which typically represents port numbers from 0 to 255.

This structured approach ensures that the interplay between port priority and port numbers facilitates efficient decision-making in the RSTP protocol. The priority influences which port is preferred in case of conflicts or multiple available paths, while the port number ensures unique identification of the specific port being referenced.

In contrast, the other options that suggest different byte allocations for either port priority or port number do not conform to the RSTP standards. For instance, options suggesting greater byte allocations (2-byte fields) would imply a more extensive range of values than is necessary for the functionality of RSTP in common networking