CompTIA A+ Core 1 (220-1201)NetworkingMedium
A technician suspects a NIC on a desktop is faulty because the computer cannot connect to the network. To isolate whether the issue is with the NIC hardware itself, the technician plugs a small connector into the Ethernet port that redirects transmit signals back into the receive pins. Which tool is being used?
- ALoopback plug
- BToner probe
- CCable crimper
- DPunch-down tool
Show answer & explanationAnswer & explanation
Correct answer: A. Loopback plug
A loopback plug redirects the transmit (TX) pins back to the receive (RX) pins, allowing a technician to test whether a NIC or port can send and receive signals without needing an actual network connection.
Why the other options are wrong
- B. A toner probe is used to trace cables through walls, not test NIC hardware.
- C. A cable crimper attaches connectors to cable ends, it doesn't test ports.
- D. A punch-down tool terminates wires into keystone jacks or patch panels.
Loopback Plug
A loopback plug is a small hardware device inserted into a network or serial port that redirects outgoing signals back as incoming signals, used to test port functionality.
- Tests NIC send/receive capability in isolation
- Common for Ethernet and serial port diagnostics
- No actual network cable or switch connection required
Memory trick: Loopback: what goes out comes right back in.