220-1101 Question 173
Single answerCable testerA technician has terminated both ends of a new Cat 6 Ethernet cable for a desktop rollout. When the cable is connected, the PC intermittently loses network connectivity and drops from 1 Gbps to 100 Mbps. The technician wants to verify that each wire is pinned correctly and that there are no opens, shorts, or crossed pairs before re-terminating the cable. Which tool should the technician use first?
- A
Cable tester
- B
Tone generator and probe
- C
Multimeter
- D
Loopback plug
Show answer and explanation
Correct answer: A
Explanation
For twisted-pair Ethernet troubleshooting, a cable tester is the standard first-step tool when the goal is to validate the physical cable and termination quality. In real-world support, link speed dropping from 1000BASE-T to 100BASE-T often indicates that not all four pairs are functioning properly, since Gigabit Ethernet requires all four pairs, while 100BASE-TX uses only two pairs. A proper cable tester helps confirm wiremap faults such as opens, shorts, reversals, crossed pairs, and sometimes split pairs, which are common causes of poor or unstable link negotiation. This aligns with structured cabling best practices used in the field and with common CompTIA A+ Core 1 expectations for matching troubleshooting tools to specific network cabling problems.
- A. Correct.
Correct. A cable tester is the appropriate first tool for verifying Ethernet cable continuity and wiremap. It can identify common faults such as opens, shorts, crossed pairs, reversals, and split pairs depending on the tester model. In this scenario, the symptoms of intermittent connectivity and fallback from 1 Gbps to 100 Mbps strongly suggest a cabling or termination issue, and a cable tester is specifically designed to confirm whether the twisted-pair cable was terminated correctly.
- B. Incorrect.
Incorrect. A tone generator and probe are primarily used to trace a cable through walls, ceilings, patch panels, or bundles when the technician needs to identify which physical cable is which. They do not provide the detailed wiremap and fault detection needed to confirm proper pinout and pair integrity for Ethernet terminations.
- C. Incorrect.
Incorrect. A multimeter can test for basic continuity or voltage, but it is not the best first choice for validating Ethernet pinout across all eight conductors. It does not efficiently identify network-specific wiring faults such as crossed pairs or split pairs in the way a cable tester does. A multimeter is more commonly used for electrical measurements than structured cabling validation.
- D. Incorrect.
Incorrect. A loopback plug is used to test whether a network interface or port can send and receive signals back to itself. It helps isolate NIC or port problems, but it does not verify whether the horizontal cable is terminated correctly or whether there are opens, shorts, or miswired pairs in the cable run.