N10-009 Question 3
Single answerLayer 1 - PhysicalA technician is asked to extend network connectivity from a switch in one building to a small office in another building approximately 180 meters (590 feet) away. The path between the buildings runs alongside a parking lot with large electric motors and lighting equipment, and the area is prone to thunderstorms. The office needs a reliable 1 Gbps connection. Which of the following is the BEST Layer 1 solution?
- A
Install Cat 6 UTP between the buildings because 1 Gbps Ethernet is supported on copper
- B
Install single-mode or multimode fiber between the buildings with appropriate transceivers
- C
Install Cat 5e STP between the buildings and bond the shielding at both ends
- D
Install a copper Ethernet run with a PoE injector to overcome the distance limitation
Show answer and explanation
Correct answer: B
Explanation
For Network+ physical-layer scenarios, the best practice for interbuilding cabling is typically fiber optic cable rather than copper, especially when the distance exceeds 100 meters or when there is significant electromagnetic interference, lightning risk, or possible ground potential differences between buildings. TIA/EIA structured cabling guidance and Ethernet standards support the 100-meter maximum for twisted-pair Ethernet channels, while fiber is commonly recommended for campus and building-to-building backbone links. In this scenario, fiber meets the 1 Gbps requirement, avoids EMI from nearby electrical equipment, and provides electrical isolation that copper cannot.
- A. Incorrect.
This is incorrect. Although 1000BASE-T can run at 1 Gbps over copper, standard twisted-pair Ethernet has a maximum horizontal channel length of 100 meters. A 180-meter run exceeds Ethernet copper specifications. In addition, copper between buildings is vulnerable to electromagnetic interference and electrical potential differences, especially in areas with lightning exposure.
- B. Correct.
This is correct. Fiber optic cabling is the best physical-layer solution for an interbuilding link at 180 meters requiring 1 Gbps. Fiber easily supports this distance, is immune to electromagnetic interference from motors and lighting equipment, and does not conduct electricity, which helps protect against lightning-related surges and grounding issues between buildings. Either multimode or single-mode fiber could support 1 Gbps at this distance, depending on the chosen optics and design standards.
- C. Incorrect.
This is incorrect. Shielded twisted pair can reduce the effects of electromagnetic interference, but it does not solve the 100-meter Ethernet distance limit for copper. It also remains a conductive medium, so it is still a poor choice for building-to-building runs where lightning and grounding differences are concerns. Some candidates choose this because STP sounds like the right answer for EMI, but the distance and surge risk make it unsuitable here.
- D. Incorrect.
This is incorrect. PoE injectors provide power over Ethernet; they do not extend standard Ethernet data distance beyond the physical-layer limit for twisted-pair cabling. Copper would still exceed the supported length at 180 meters and would still be susceptible to interference and electrical hazards in this environment.