Which of the following is used to confirm that a physical port is working?

A loopback plug is a diagnostic tool used to test whether a physical port such as an Ethernet NIC port or serial port is capable of sending and receiving its own signal. When inserted, it “loops” outgoing signals back into the device, confirming the port ' s transmit/receive functionality.

CompTIA A+ emphasizes loopback plugs as essential tools during hardware and network troubleshooting, especially when isolating physical port or NIC failures.

Network taps passively monitor traffic, crimpers attach RJ45 connectors to cables, and patch panels organize cabling none of these verify port-level functionality. Therefore, only a loopback plug can confirm that a port is working correctly by testing signal integrity and hardware responsiveness.