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Chapter 5
Network Cabling
Review Questions
1. Which transmission characteristic is never fully achieved?
a. Latency
b. Throughput
c. Bit rate
d. Bandwidth
2. Which kind of crosstalk occurs between wire pairs near the source of the signal?
a. Alien
b. Tx/Rx reverse
c. FEXT
d. NEXT
3. Which kind of multiplexing assigns slots to nodes according to priority and need?
a. WDM (wavelength division multiplexing)
b. STDM (statistical time division multiplexing)
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c. TDM (time division multiplexing)
d. CWDM (coarse wavelength division multiplexing)
4. What kind of cable uses BNC connectors? Which connector is likely to be used
by cable TV?
a. Coaxial cable, F-connector
b. Twisted-pair cable, RJ-11
c. Copper cable, RJ-45
d. Fiber-optic cable, MTRJ
5. Which of these categories of twisted-pair cable can support Gigabit Ethernet?
a. Cat 5, Cat 6, Cat 7
b. Cat 5e, Cat 6, Cat 3
c. Cat 5e, Cat 6a, Cat 7
d. Cat 6, Cat 7a, Cat 5
6. Suppose you’re creating patch cables to be used in a government office. What
color wire goes in the first pin?
a. White/orange
b. White/green
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c. Brown
d. Blue
7. What is the earliest twisted-pair cabling standard that meets the minimum
requirements for 10GBase-T transmissions?
a. Cat 5e
b. Cat 5
c. Cat 6a
d. Cat 7
8. What type of fiber cable problem is caused when pairing a 50-micron core cable
with a 62.5-micron core cable?
a. Dirty connectors
b. Wavelength mismatch
c. Fiber type mismatch
d. Tx/Rx reverse
9. Which part of a toner and probe kit emits an audible tone when it detects
electrical activity on a wire pair?
a. TDR
b. Tone generator
c. Tone locator
d. Toner
10. Which fiber connector contains two strands of fiber in each ferrule?
a. MTRJ
b. SC
c. ST
d. LC
11. How is latency measured, and in what unit?
12. What is a twist ratio, and why is it important?
13. What fiber is used in fiber-optic cabling to protect the inner core and prevent the
cable from stretching?
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14. What characteristic of optical transmissions is primarily responsible for the
distance limitations of fiber-optic cabling?
15. Why is SMF more efficient over long distances than MMF?
16. Why do APC ferrules create less back reflection than UPC ferrules?
17. Which fiber transceiver is the same size as SFP transceivers, but can support
network speeds over 10 Gbps?
18. Suppose you’re assisting with a cable installation using fiber-optic cabling that
will support Gigabit Ethernet. You’re approved to install segments up to 4000 m
in length. What kind of cable are you using?
19. What is the difference between short circuits and open circuits?
20. What kind of tool can measure the distance to the location of damage in a cable?
Hands-On Projects
Project 5-1: Create a Loopback Plug
In this chapter, you practiced terminating an Ethernet cable by attaching an RJ-45
connector. You also learned that a loopback plug crosses the transmit line with the
receive line to trick a device into thinking it’s connected to a network. You can create
your own loopback plug by altering the pinout on the connector and forcing the
transmissions to loop back in on themselves. A loopback plug is helpful for determining
if a NIC on a workstation or a port on a switch is working or not.
To make your own loopback plug, you’ll need a 6-inch length of UTP cabling (Cat 5 or
Cat 5e), an unused RJ-45 plug, wire cutters, and a cable crimper.
1. Cut to loosen the cable’s covering, then slide the covering off the cable and flatten
2. Untwist the wires on each end an inch or less and straighten out the tips. If
3. Insert one end of the twisted pair into the RJ-45 plug, making sure the solid color
4. Loop the wire pair around and insert the other end into the plug. The solid color
5. Push the wires all the way in, and use the crimper to secure the wires in the plug.
If a boot came with the plug, you can insert it over the wire loop and push it all
the way through to cover the wire/plug connection, as shown in Figure 5-48.
6. Insert the loopback plug into a device’s Ethernet port that is known to be working
correctly and has LED indicator lights. If the port’s link indicator lights up (this
might take a minute), you’ve successfully created a loopback plug.
Project 5-2: Create a Loopback Jack
A loopback plug can be used to test a port on a switch or a workstation’s NIC. A
loopback jack, however, can be used to test a cable or to identify which port a cable is
connected to. This is especially helpful when the cable is already run through the wall or
is tangled up with other cables.
Creating a loopback plug is pretty straightforward, and wiring a loopback jack is even
easier. For this project, you’ll need a 2-inch length of UTP cabling (Cat 5 or Cat 5e), an
unused RJ-45 data/phone jack (these are very inexpensive and easily found at many home
improvement stores), and a punchdown tool.
1. Cut to loosen the cable’s covering, slide the covering off the cable, select one wire
2. Turn the jack so the slots are easily accessible. Take a single wire and press one
3. Take the other, single wire, press one end into the slot next to the “A—orange”
icon, and press the other end into the slot next to the “A—green” icon. In some
4. Use the punchdown tool to punch the wires all the way into their respective slots.
The punchdown tool will also clip the excess length off the wires. Make sure to
5. To test your loopback jack, plug a patch cable you know to be good into a
device’s Ethernet port that you know works, then plug the jack onto the other end
of the cable. Wait up to a minute to give the link sufficient time to be established.
If the port’s link indicator lights up, you’ve successfully created a loopback jack.
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[[Insert Figure 5-50 here]]
Project 5-3: Latency Around the World
In this chapter, you learned that latency is the delay caused by the time it takes messages
to travel over network media from one place to another. This concept is easy to see in the
real world, where it takes longer, for example, for you to travel across the country than it
does to go to the grocery store. Even though network messages travel much faster than a
car or a jet plane, it still takes time for them to get from one place to another.
Complete the following steps to see how distance affects a message’s RTT (round trip
time):
1. Open a Command Prompt window and run tracert on a website whose servers
are located on a different continent from you, across one ocean. If you’re located
in the Midwest or Eastern United States, for example, you can run the command
tracert london.edu (London Business School). If you are on the West
Coast, however, you might get more useful results for this step by targeting a
server across the Pacific Ocean, such as tracert www.tiu.ac.jp (Tokyo
International University). What command did you use?
2. Examine the output and find the point in the route when messages started jumping
across the ocean. By what percentage does the RTT increase after the jump
compared with before it? You can see an example in Figure 5-51.
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[[Insert Figure 5-51 here]]
To calculate the percentage for this jump, you would select a time from just after
the jump (229, for example) and divide it by a time from just before the jump
(such as 39), then multiply by 100 percent: 229 / 39 × 100 = 587. In this case, the
sample data would yield a 587 percent increase. It takes nearly six times as long
for a message to go round-trip across the Atlantic from the United States to
London, England (the location of this first European router) as it does for a
message to travel round trip between two servers that are both located on the U.S.
East Coast (this local computer, and the last U.S. router in the route).
3. Choose a website whose servers are on a continent even farther away from you.
For example, if you are in the United States, you could trace the route to the
University of Delhi in India at the address du.ac.in. What command did you use?
How many hops did it take until the route crossed an ocean? What other
anomalies do you notice about this global route?
4. Choose one more website as close to directly across the globe from you as
possible. U.S. locations might want to use the University of Western Australia at
uwa.edu.au. What command did you use? How many hops are in the route? Did
the route go east or west around the world from your location? How can you tell?
5. Scott Base in Antarctica runs several webcams from various research locations.
Run a trace to the Scott Base website at antarcticanz.govt.nz. What’s the closest
router to Scott Base’s web server that your trace reached? If you can’t tell from
the command output where the last response came from, go to iplocation.net in
your browser. Enter the final IP address to determine that router’s location.
6. Think about other locations around the world that might be reached through an
interesting route. Find a website hosted in that location and trace the route to it.
Which website did you target? Where is it located? What are some locations
along the route of your trace?
7. Try the ping command on several of these same IP addresses. Did it work? Why
do you think this is the case?
Project 5-4: Test a LAN’s Speed and Throughput
A variety of software and web-based tools are available to help you establish baseline
measurements—and later, detect fluctuations and problems—in the efficiency of your
network and Internet connections. This project walks you through two different tests you
TotuSoft’s LAN Speed Test is a simple, free program that only needs access to a shared
folder on the local area network in order to test throughput speeds on the network. The
Public Users folder on another workstation meets this requirement.
To test a wired network connection, make sure both your computer and the target
computer have a physical connection to the network (rather than a Wi–Fi connection), and
then complete the following steps:
1. Go to totusoft.com, download the latest version of LAN Speed Test (Lite), and
2. Find a shared folder on another workstation or a server on your network, as
shown in Figure 5-52. Select the folder as the target, accept the default settings,
and start the test.
3. Accept the default settings for the test, including file size and the option to delete