220-1101 Question 155
Single answerFiberA technician is connecting a new 10 Gbps fiber uplink between a wiring closet switch and a distribution switch in another building. The run is approximately 250 meters and passes near elevator motors and other sources of electromagnetic interference. The switches support either copper or fiber transceivers. Which solution is the MOST appropriate for this installation?
- A
Use Cat 6a UTP because 10 Gbps is supported and twisted-pair cabling is easier to terminate
- B
Use single-mode fiber because any inter-building fiber link must use the longest-distance option available
- C
Use multimode fiber with appropriate 10 Gbps optics because the distance is moderate and fiber is immune to EMI
- D
Use coaxial cable because it provides better shielding than fiber and supports backbone links
Show answer and explanation
Correct answer: C
Explanation
The best answer is to use multimode fiber with the proper 10 Gbps transceivers. In A+ Core 1, candidates should recognize that fiber is preferred when a network link must span beyond standard twisted-pair Ethernet distance limits or operate in environments with significant EMI. Copper Ethernet over twisted pair is generally limited to 100 meters, so a 250-meter run rules out Cat 6a for a standard 10GBASE-T switch uplink. Fiber cabling is also nonconductive and immune to electromagnetic interference, making it ideal near motors and heavy electrical equipment. In practice, the exact supported distance depends on the multimode fiber type and the optics used, but the scenario clearly points to fiber as the appropriate medium. This aligns with common networking best practices and vendor documentation for Ethernet media selection based on distance, bandwidth, and environmental conditions.
- A. Incorrect.
This is incorrect. Cat 6a can support 10GBASE-T up to 100 meters under standard Ethernet limits, but the scenario specifies a 250-meter run, which exceeds copper Ethernet distance limitations. In addition, copper is more susceptible to electromagnetic interference than fiber, making it a poor choice near elevator motors and similar equipment.
- B. Incorrect.
This is incorrect. Single-mode fiber can support much longer distances than multimode and is commonly used for long campus or metro links, but it is not required simply because the link is between buildings. For a 250-meter 10 Gbps run, multimode fiber can be an appropriate and cost-effective choice when paired with the correct optics. Choosing single-mode solely because it is the longest-distance option is not the best justification.
- C. Correct.
This is correct. A 250-meter 10 Gbps uplink is a common use case for fiber, and multimode fiber is often used for relatively short-to-moderate building and campus backbone links when the optics and cable type support the required distance. Fiber is also immune to electromagnetic interference, which is important in an area with elevator motors and other EMI sources.
- D. Incorrect.
This is incorrect. Coaxial cable is not the standard choice for modern 10 Gbps Ethernet uplinks between switches. Although coax can provide shielding, it is not the practical or expected medium for this type of backbone connection. Modern switched network uplinks at this speed and distance are typically implemented with fiber.