3.4.7 Practice Questions

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3.4.7 Practice Questions Date: 11/4/2023 5:58:09 pm • Time Spent: 05:57 Score: 100% Passing Score: 80% You've decided to implement Gigabit Ethernet on your network; each switch port is connected to a single device. Following the installation, you find one device connected to a switch that's only running at 100 Mbps. Which of the following is MOST LIKELY the cause? Answer Impedance A short Collisions Correct Answer: Crosstalk Explanation Crosstalk is interference caused by signals within a twisted pairs of wires. Crosstalk and other miswiring problems typically mean that a cable doesn't operate at the desired standard. Use a cable certifier to verify that the cable is properly configured to support the rated speed. A short is when the signal is received on an incorrect wire. A short typically means the cable doesn't work at all or communications are very limited and extremely slow.

Collisions are eliminated when you connect a single device to each switch port. Impedance is mostly a factor in coaxial cables used for networking. Be sure to choose cables with the correct rating (50 or 75 ohm) based on the network type. Never mix cables that have different ratings. References q_trouble_wire_crosstalk_np6.question.fex You have a cable internet connection at home. The installer had connected the router near the outside wall of your house with RG6 cable. You move the cable router a distance of 50 meters using RG8 cables and special connector adapters. Which condition are you MOST LIKELY to experience? Answer FEXT Correct Answer: Echo NEXT EMI Explanation An impedance mismatch (manifested by echo) occurs when you connect cables and devices that have a different impedance (resistance) rating. RG6 cables have a rating of 75 ohms, while RG8 cables have a rating of 50 ohms. Near-end crosstalk (NEXT) is crosstalk measured on the same end as the transmitter.

Far-end crosstalk (FEXT) is crosstalk measured on the opposite end from the transmitter. Electromagnetic interference (EMI) and radio frequency interference are external signals that interfere with normal network communications. References q_trouble_wire_echo_np6.question.fex While viewing the status of interfaces on a Cisco switch, you see an abnormally large number of CRC errors on one interface. This interface is connected to a user's workstation that is located in a cubicle on the second floor. What could cause this to happen? Answer Correct Answer: A strong EMI emitter near the cable connected to that interface. Two hosts on the network with the same MAC address. An incorrect subnet mask configured on the workstation. Collisions between two or more network hosts. Explanation The most likely cause is EMI or crosstalk on the UTP cabling, which can corrupt frames transmitted on the wire and cause a CRC error. On a hub-based Ethernet network, these errors are usually caused by collisions. However, because a switch is being used in this scenario, collisions can't occur.

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CRC errors are almost always Layer 1 errors. Duplicate MAC addresses would result in a Layer 2 error. Incorrect protocol or IP addressing configurations result in Layer 3 errors. References q_trouble_wire_emi_np6.question.fex You need to replace a fiber optic cable that's connecting two switches together. You inspect the existing cable and determine that it uses LC connectors. You also notice that the cable's ferrule has a slight slant to it. Which polish grade should you use to replace the existing cable? Answer Physical Contact polish Correct Answer: Angled Physical Contact polish Flat Physical Contact polish Ultra Physical Contact polish Explanation A slight slant to the fiber ferrule indicates an Angled Physical Contact (APC) polish. Using a non-angled connector will cause excessive insertion loss. A Physical Contact (PC) polish is polished with a slight curvature.

An Ultra Physical Contact (UPC) polish uses a higher grade polish and is slightly more curved than a PC polish. A Flat Physical Contact connector has little to no curvature and suffers from the most insertion loss. References q_trouble_fiber_apc_01_np6.question.fex You're building a new network for a small financial services startup company. Security is paramount, so each organization within the company will have its own network segment separated by a router. However, funds are limited, and you've been asked to keep costs to a minimum. You've acquired a used fiber optic switch, and you want to use it to create a fiber optic backbone that interconnects all of the routers. You've purchased several used single-mode GBIC modules on eBay that you'll install on each router to allow them to connect to the switch. Both the switch and the GBIC modules use MTRJ connectors. You connect each module to the switch with 1-meter multimode patch cables. Will this implementation work? Answer Correct Answer: No. You shouldn't use multi-mode patch cables with single-mode GBIC modules. No. You should purchase fiber optic equipment that use FC connectors. Yes. All of the requirements for implementing a fiber optic network have been met. No. You shouldn't use standard fiber optic switches to create a backbone network for routers.

Explanation Some GBIC/SFP modules use multi-mode fiber, while others use single-mode. You must use the correct type of fiber optic cable and connector required by the specific adapter. You can't mix and match different types of cable. In this scenario, connecting a single-mode GBIC to multi-mode fiber will introduce a catastrophic signal loss of up to 99%. References q_trouble_fiber_mix_np6.question.fex You're building a new network for a small financial services startup company. Security is paramount, so each organization within the company will have their own network segments separated by routers. Funds are limited, and you've been asked to keep costs to a minimum. You've acquired a used fiber optic switch, and you want to use it to create a fiber optic backbone that interconnects all of the routers. You've purchased several used multi-mode GBIC modules on eBay that you'll install on each router to allow them to connect to the switch. Both the switch and the GBIC modules use MTRJ connectors. You've purchased several used 1-meter, multi-mode patch cables from Amazon. But when they arrived, you noticed that they use LC connectors. Fortunately, with some force, you found that you're able to get the LC connectors on the cables to lock into the MTRJ connectors on the GBIC modules and on the switch. Will this implementation work? Answer Yes. All of the requirements for implementing a fiber optic network have been met. No. You should use a specialized backbone fiber optic switch to create a backbone network for routers. Correct Answer: No. You should purchase patch cables that use MTRJ connectors.

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No. You should use single-mode patch cables to connect a GBIC module to a switch. Explanation For light to pass through a fiber optic connector, the fiber within the jack must line up perfectly with the fiber in the connector. Using the wrong connector will result in misaligned fibers. This will disrupt the light signal, even if you're able to successfully lock the connector into the jack. In this scenario, you should purchase patch cables that use MT-RJ connectors. References q_trouble_fiber_mtrj_np6.question.fex You want to measure the voltage, amps, and ohms of various devices. Which tool should you use? Answer Toner probe Certifier Voltage event recorder Correct Answer: Multimeter Explanation A multimeter is a device that tests various electrical properties. For example, most multimeters can measure:

AC and DC voltage Current (amps) Resistance (ohms) Capacitance Frequency A voltage event recorder tracks voltage conditions on a power line. Basic recorders keep track of the occurrence of under- or over-voltage conditions, while more advanced devices track conditions over time and create a graph, saving data from a program running on a computer. A toner probe is two devices used to trace the end of a wire from a known endpoint onto the termination point in the wiring closet. A cable certifier is a multi-function tool that verifies or validates that a cable or an installation meets the requirements for a specific architectural implementation. References q_trouble_tools_multimeter_np6.question.fex You're working with an existing fiber optic installation in your building. You want to know the length of each cable that runs through the walls. Which tool should you use? Answer Correct Answer: OTDR Multimeter

Smartjack Toner probe Explanation An optical time domain reflector (OTDR) sends light pulses on a cable to discover information about the cable. The results of this test can be used to: Estimate a wire's length. Measure a cable's impedance. Identify locations of splices and connectors on a wire. Identify shorts, open circuits, and fault locations. Use a toner probe to locate the end of a wire from a wall jack to the punchdown block. Use a multimeter to measure a device's electrical properties, such as voltage, amps, and resistance. A smartjack is a special loopback plug installed at a WAN service's demarcation point. References q_trouble_tools_otdr_np6.question.fex Users report that the internet is no longer accessible. You suspect that the line connecting your building to the internet isn't working properly. Which of the following allows the service provider to remotely test the local loop? Answer Correct Answer:

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Smartjack Demarc extension Horizontal cross connect Demarc Explanation A smartjack is a special loopback plug installed at a WAN service's demarcation point. Technicians at the central office can send diagnostic commands to the plug to test connectivity between the central office and the demarc. The demarcation point (demarc) is the line that marks the boundary between telco equipment and the private network or telephone system. A demarc extension extends the demarcation point from its original location to another location within the building. A horizontal cross connect connects wiring closets on the same floor. References q_trouble_tools_smartjack_np6.question.fex An illustration of a cable pinout, 1 to 3, 2 to 6, 3 to 1, 4 to 7, 5 to 8, 6 to 2, 7 to 4, and 8 to 5. You've connected a cable certifier to an RJ45 wall jack, and the output shown below is displayed on the device. What does this output indicate? (Select two.) Answer There are multiple shorts on this cable.

This is a straight-through cable. Correct Answer: The cable is functioning correctly. Correct Answer: This is a crossover cable. There are multiple open pins on this cable. Explanation In this display, the cable being tested is a correctly wired crossover cable. Output with (x) characters between pins indicates that they're shorted. Straight-through connections are displayed using (-) characters in the cable certifier's output. Open connections are displayed with no characters or lines between pin numbers. References q_trouble_tools_tester_01_np6.question.fex