N10-009 Question 302
Single answerA technician installs a new 10GBASE-T link between a core switch and a virtualization host in a manufacturing area. The cable run is approximately 60 meters and passes through trays alongside motor power lines and variable-frequency drives. After the upgrade, the link comes up at 10 Gbps but users report intermittent retransmissions and poor throughput during business hours when the machinery is active. A cable tester shows excessive alien crosstalk and EMI-related errors, but no opens or shorts. Which of the following is the BEST corrective action?
- A
Replace the existing Cat 5e UTP with properly terminated Cat 6a STP and ensure the shielding is bonded according to the manufacturer guidelines
- B
Replace the existing patch panels with multimode fiber transceivers to reduce attenuation on the copper run
- C
Re-terminate the cable using a rollover pinout to correct possible TX/RX transposition between the switch and server
- D
Shorten the run to under 100 meters and keep the existing Cat 5e UTP because 10GBASE-T is supported on any copper cable under the maximum distance
Show answer and explanation
Correct answer: A
Explanation
The best answer is to replace the Cat 5e UTP with properly terminated Cat 6a STP and bond the shielding correctly. In real deployments, 10GBASE-T is commonly run over Cat 6a for up to 100 meters. Cat 5e is not the proper choice for a new 10 Gbps horizontal run, especially in a manufacturing space with significant electromagnetic interference. EMI from motors and variable-frequency drives can degrade copper Ethernet performance, and alien crosstalk becomes more significant at higher frequencies used by 10GBASE-T. CompTIA Network+ objectives expect candidates to distinguish among cable categories and shielding types, and to recognize symptoms of signal degradation such as crosstalk, interference, and attenuation. TIA/EIA structured cabling practices and manufacturer installation guides also stress correct termination and proper bonding/grounding when shielded cabling is used; improperly terminated STP can perform poorly or unpredictably. The other answers include common misconceptions: using rollover wiring for Ethernet, assuming any sub-100-meter copper run supports 10GbE, or proposing an imprecise fiber 'replacement' that does not match the troubleshooting evidence.
- A. Correct.
Correct. This scenario points to interference and crosstalk in a high-EMI industrial environment. Cat 5e is not the appropriate choice for a 60-meter 10GBASE-T run, and UTP is more susceptible to external interference when routed near motors and VFDs. Cat 6a is the commonly recommended cabling standard for 10GBASE-T up to 100 meters, and using STP in electrically noisy areas can help mitigate EMI when installed and grounded/bonded properly. The mention of proper termination also matters because poor shield termination can reduce or negate the benefits of shielded cabling.
- B. Incorrect.
Incorrect. Multimode fiber can be a valid medium for high-speed uplinks, but this option is technically flawed and does not address the stated problem correctly. Patch panels are not replaced with transceivers, and multimode fiber transceivers are not a direct fix for a copper cabling issue in the way described here. Also, the tester specifically identified alien crosstalk and EMI-related issues on the copper installation, suggesting the immediate best answer is to use the proper copper category and shielding for the environment rather than this mismatched solution.
- C. Incorrect.
Incorrect. TX/RX transposition is a wiring issue more commonly associated with crossover/straight-through mismatches or fiber pair polarity concerns, not with 10GBASE-T performance degradation caused by EMI and alien crosstalk after the link successfully negotiates. A rollover cable is used for console connections, not Ethernet data links, so this option reflects a common but incorrect confusion between cable types.
- D. Incorrect.
Incorrect. Although Ethernet standards define maximum channel lengths, being under 100 meters does not mean any copper category will support 10GBASE-T reliably. Cat 5e does not provide the expected 10GBASE-T support for this 60-meter industrial scenario, especially with documented alien crosstalk and EMI exposure. The misconception here is assuming distance alone determines suitability, while cable category and environmental conditions are also critical.