220-1101 Question 174
Single answerLoopback plugA technician is troubleshooting a desktop that cannot connect to the network after a motherboard replacement. The NIC link light is off even when a known-good patch cable is connected to a known-good switch port. To determine whether the network adapter can transmit and receive signals internally before replacing more parts, which tool should the technician use?
- A
A loopback plug connected to the NIC port
- B
A tone generator connected to the switch port
- C
A cable tester connected to both ends of the patch cable
- D
A multimeter set to continuity mode on the Ethernet pins
Show answer and explanation
Correct answer: A
Explanation
The best answer is a loopback plug. In A+ Core 1 troubleshooting, a loopback plug is a standard diagnostic tool used to verify whether an interface port can transmit and receive data through itself, helping isolate the problem to the adapter rather than the cable or network equipment. This is especially useful when a known-good cable and switch port have already been ruled out. By contrast, a tone generator traces cables, a cable tester validates cable integrity, and a multimeter is not the proper tool for functional Ethernet port testing. This approach aligns with common hardware troubleshooting best practices: isolate the component under test and verify local functionality before replacing external infrastructure or additional hardware.
- A. Correct.
Correct. A loopback plug is used to test whether a network interface can send and receive through its own port by looping transmitted signals back to the receiver. In this scenario, it helps isolate the NIC from the external cable and switch infrastructure to determine whether the adapter hardware is functioning.
- B. Incorrect.
Incorrect. A tone generator is commonly used to trace cable runs and identify wiring paths, not to verify that a NIC can internally transmit and receive data. It would not directly test the network adapter's port functionality.
- C. Incorrect.
Incorrect. A cable tester is useful for checking whether the patch cable is wired correctly and free of opens, shorts, or split pairs. However, the scenario already states that a known-good cable and switch port are being used, and a cable tester does not test the NIC's internal send/receive operation.
- D. Incorrect.
Incorrect. A multimeter continuity test is not an appropriate method for validating Ethernet NIC operation. Ethernet ports contain active circuitry and signal characteristics that cannot be meaningfully verified with a simple continuity check, and probing pins this way does not confirm transmit/receive functionality.