The 'Protocol' field of the show ip interface brief command shows the Layer [...] status of the interface.

The 'Protocol' field of the show ip interface brief command indicates the Layer 2 status of the interface. In the context of networking, Layer 2 deals with data link layer protocols that manage communication between devices on the same physical network. This includes the functionality provided by switches and the status of protocols such as Ethernet.

When the protocol status is up, it indicates that the interface is operational and able to participate in data communication, meaning it can successfully send and receive frames. Conversely, a down status would signify a problem at the data link layer, such as a physical disconnection or misconfiguration.

In contrast, the Layer 1 status refers to physical layer characteristics, such as whether the physical medium is connected. Layer 3 refers to network layer functions like IP addressing and routing. Layer 4 corresponds to transport layer protocols such as TCP and UDP. Therefore, the correct identification of the Layer 2 status in the 'Protocol' field is essential for troubleshooting network interfaces effectively.