COMPTIA A+
220-901
STUDY GUIDE
BY POWERCERT
Written by Scott Prieto
From the creator of PowerCert Animated Videos
on
Version 2.0
This ebook is designed to study for the
CompTIA A+ 220-901 exam.
Check out my youtube channel:
PowerCert Animated Videos
© PowerCert 2017. All rights reserved. No part of this document
may be reproduced nor transmitted in any form, by any means
(electronic, photocopying, recording, or otherwise) without the prior
written permission of the author.
TABLE OF CONTENTS
1 input Devices & Peripherals
Keyboards, mouse, digital cameras,
barcode scanners, scanners,
touchscreens, webcams, card
readers, docking stations, KVM
switches, smart TVs, biometric
devices, motion sensors, digitizers,
gamepads & joysticks.
12 Monitors
CRT, LCD, LED, TN vs IPS
backlighting, degauss, resolutions.
19 printers
Inkjet, laser, thermal, dot matrix,
printer issues, trouble shooting,
virtual printing.
31 storage devices
Hard drives, SSD, tape drives, CD,
DVD, Blu ray drives, discs, SD cards,
eMMC.
39 power supply
Power supply, connectors.
42 motherboard
Motherboard, form factors, ATX, AT,
Micro ATX, BTX, NLX, ITX.
46 motherboard i/o interfaces
PS/2, USB, serial, parallel, firewire,
NIC, video, sound, eSATA, eSATAp.
53 adapter / expansion cards
Video card, VGA, DVI, S-Video, HDMI,
DisplayPort, sound, USB, RAID,
eSATA, video capture, TV tuner, NIC,
wireless NIC,
62 ram (memory) slots
DIMM, SIMM, bit vs byte, data paths
64 ram
DRAM, SRAM, SDRAM, DDR,
bandwidth, dual channel, triple
channel, single-sided vs double
sided, ECC, SODIMM, buffered vs
unbuffered.
77 cooling
Case fans, passive vs active cooling,
heatsink, thermal compound, water
cooling.
83 cpu, socket, & chipset
ZIF, PGA, LGA, Intel & AMD socket
types & CPUs, CPU core, 32 vs 64-bit,
memory cache, northbridge,
southbridge, buses, hyper-threading.
98 bus slots
PCI, PCI express, PCI-X, mini PCI.
102 mobile issues - PHONES & LAPTOPS
Not responsive, apps not loading,
slow performance, GPS, no display,
dim display, inverter, flickering
monitor, keys sticking, ghost cursor,
overheating, battery not charging,
intermittent wireless connection.
111 bios/cmos
BIOS, CMOS, battery, settings, POST,
beep codes, UEFI, secure boot.
121 Front Panel Connector
Motherboard connector, front USB &
audio ports, power & reset buttons,
drive activity light.
123 RAID
RAID levels 0, 1, 5, 10.
128 networking cables & connectors
RJ-11, RJ-45, BNC, F-type, firewire,
USB, thunderbolt, RCA, LC, ST, SC,
plenum vs non plenum, powerline
network adapter, HDMI, wiring
standards.
139 firewall
Host-based firewall.
140 media types
Twisted pair cable categories, UTP,
STP, coaxial cable, single & multimode fiber.
144 network components
Cable modem, hub, switch, bridge,
router, PoE, wireless access point,
NIC, MAC address, modem card,
patch panel.
150 wireless technologies
Wireless standards, bluetooth.
151 ip address
IPv4, IPv6, subnet mask, public &
private IP addresses.
157 ip addressing methods
DHCP, dynamic, static, APIPA.
160 tcp/ip protocol suites
TCP, UDP, DNS, NAT, FTP, SFTP,
TFTP, SMTP, POP3, IMAP4, HTTP,
HTTPS, telnet, SSH, SNMP, ports.
170 ports
Port numbers and services.
171 internet access technologies
DSL, ADSL, SDSL, VDSL, broadband
cable, POTS/PSTN, ISDN, satellite,
mobile hotspot.
176 network types
PAN, LAN, MAN, WAN.
178 networkING TOOLS
Wire crimper, punch down tool,
media tester, cable stripper,
multimeter, tone generator,
182 soho routers, wifi encryption
DHCP, SSID, channels, WEP, WPA,
WPA2, WPS, MAC filter, DMZ.
193 Network Utilities
Ping, traceroute, nbtstat, netstat,
ipconfig, ifconfig, default gateway,
nslookup, dig.
Input Devices &
Peripherals
One of the most basic input devices on a computer is a
keyboard. A keyboard is a device that is used to input
commands to the computer. It has keys that are made
up of alphabets, numbers, and symbols that you can
press with your fingers. The most basic function of a
keyboard is to do things like word processing, write
letters, emails, visit web pages, and so on. Keyboards
come equipped with two different connector types.
There's the older 6 pin DIN connector, which has pretty
much become obsolete, and there is also the modern
USB connector. A lot of keyboards will have the ability to
use both connectors because a lot of times they will
come with a DIN to USB adapter which you can use with
any computer with either a DIN or USB connection.
Keyboard
A mouse is another basic input device that is used on a
computer. It's a pointing device that fits in the palm of
1
your hand and replicates the movement of the mouse
onto the computer screen.
Wireless mouse
Wired mouse
It’s used for things like starting applications, file and
folder management, surfing the internet, and so on. A
mouse will typically have one or two buttons. A
Macintosh mouse will have one button, while a Windows
mouse will have at least two buttons. A mouse can be
either wired or wireless.
A digital camera is a device that takes digital pictures
and videos. Unlike standard cameras, where the images
are stored on film, a digital camera stores the images on
its internal storage or SD card. Then once the images
are stored, they can be transferred to a computer by
using a USB cable or by the SD card. Then once they're
on the computer, the images can be viewed or printed.
Digital
camera with
an SD card.
2
A barcode reader is a device that is used for reading
barcodes. It uses light to scan barcodes and it's
typically used to detect point of sales and maintain
inventory. It can connect to a computer through a serial
port, USB port, or a wireless connection. Barcode
readers come in several forms, but the most popular is
the handheld trigger type.
Handheld trigger
type barcode reader
Now a scanner is a device that enables you to put a
digital copy of a physical copy, on your computer. So
for example, if you have a photo or a document and
you wanted to put a digital image of that photo or
document on your computer, well that's what a scanner
enables you to do. Scanners will typically have a
flatbed where you can place a photo or document, and
at the press of a button, it will scan it for you. Then
once it's done scanning, it will save the document or
photo to your computer. Scanners will typically come in
a combination with a printer, or you can also purchase
a scanner all by itself.
3
Flat bed scanner
A touchscreen is basically an LCD monitor with an
input detection system. It's a grid that senses the touch
by a finger.
Touchscreen monitor
It works the same way as if you were using a mouse, but
without the mouse itself because you are using your
finger instead. The touchscreen receives a touch in the
same way as if you were clicking a mouse button.
4
Typically one click of the mouse button equal one tap by
a finger, and two clicks of the mouse button equal two
taps by a finger. Touchscreens are commonly used in
all-in-one computers, and also in tablets, such as the
iPad. They're also used on certain phones with touch
screen technology.
Devices that use touchscreen technology.
All-in-one
computer
Webcam
iPad tablet
Smart
phone
A webcam is a device that is
used for capturing video and
images. Webcams are mainly
used for video conferencing and
video calling over the internet. So
any two people in the world can
visually communicate with each
other if they both have a webcam
and an internet connection.
5
Most webcams also have a built-in microphone to
capture audio. A webcam connects to a computer
through a USB cable and they are often used with
messaging applications such as Skype, for making visual
calls. Two of the biggest manufacturers of webcams are
Logitech and Microsoft.
Webcams used
during a video call.
A media card reader gives the computer the ability to
read memory cards from devices such as cameras. It's
a small device that usually has a USB cable that
connects to a computer and then the body of the reader
has slots to accommodate various sizes of memory
cards, for example, micro SD and mini SD cards. Then
once connected, the data from the memory cards can
be read and transferred to the computer.
Media card
reader
SD cards
6
A docking station is used for laptop computers. It's a
device that is used for basically turning your laptop into
virtually a desktop computer.
Docking station
We all know that laptops are generally smaller than
desktops. For example on the laptop, the monitor and
keyboard are generally small. So if you wanted to use
your laptop at your desk and you wanted to use a
bigger monitor and keyboard, you can simply set the
laptop in the docking station and it will automatically
connect to them and use them, depending on what is
already plugged into the docking station, whether it's a
monitor, keyboard, mouse, printer, etc.
Laptop in Docking
station
7
It eliminates the hassle of connecting all these devices
individually. You just simply attach the laptop into the
docking station and then start using the devices
instantly. But there's one thing to remember about
docking stations, and that is that they are specific to the
manufacturer of the laptop. So there is no such thing as
a one-size-fits-all docking station. You need to get the
specific one for the laptop.
KVM switch
A KVM switch allows you to control multiple computers
from a single monitor, keyboard, and mouse. A KVM is
typically a box with ports for a monitor, mouse, and
keyboard. Each computer has their own individual cable
connection to the KVM. Each KVM has buttons that you
can press so that you can switch to a different computer
that you want to control. KVMs also come in different
sizes, depending upon how many computers that KVM
can handle. A low-end KVM switch will have the ability to
control two computers, while a higher-end KVM can
control 8 computers. KVMs are handy when you want to
control multiple computers without the need for a
dedicated monitor, keyboard, and mouse, for each one.
This not only saves money, but it also saves space.
8
A smart TV is a television where you can not only
watch TV, but you can also connect to the internet. So
basically it's a television combined with a computer.
And when it's connected to the internet, you can go to
web pages, stream movies, and television shows. A
smart TV can also interact with other people across the
internet by using video messaging services such as
Skype because a lot of smart TVs will also have a builtin webcam and microphone.
One way to prove the identity of a person is by using a
smart card. A smart card is a good choice to prove
your identity because you always have to have it with
you when proving your identification. A smart card is
the same size as a credit card with an embedded
microprocessor chip.
Smart card reader
Smart card
9
There is also a smart card reader which is a device that
is used to accept and read smart cards.
Laptop with builtin fingerprint
scanner
A biometric device is used
to prove the identity of a
person by recognizing unique
physical characteristics, for
example, a fingerprint
scanner. Fingerprint
scanners are used to read a
user's fingerprint, to prove
authentication. These days a
lot of fingerprint scanners will
be built into a device such as
a laptop or a smartphone.
You just swipe your finger
across the fingerprint scanner
and the scanner what either
grant or deny you access
based on your fingerprint.
Another type of input device
is a motion sensor. A
motion sensor records your
hand movement in mid-air
without making any physical
contact with the device. A
motion sensor would also
typically connect to your
computer using a USB
cable.
Motion sensor
10
A digitizer is a device that is used to convert analog
movement, such as a hand drawing, and convert it into
a digital form on your computer. It's a tablet with a
stylus, and as you draw on the flat surface using a
stylus, it will record the image from the stylus and
process the drawing on your computer screen. A
digitizer typically connects to your computer using a
USB cable.
Digitizer
Other input devices include gamepads and
joysticks. These are controllers that would typically
be used for gaming systems, such as Xboxes and
PlayStations. But you can also use these for
computers, and if you're going to use these with a
computer, they would typically connect using a USB
connection.
Gamepad
Joystick
11
Monitors
The computer monitor is a primary output component
of a computer. It connects to the computer's video
adapter through a monitor cable and displays images on
the screen. A computer monitor may have a VGA, DVI,
HDMI, or a DisplayPort.
CRT Monitor
LCD Monitor
Now an older type of monitor is called CRT. CRT
stands for a cathode ray tube, which was the technology
first used in TV sets. These monitors are bulky and
heavy and take up a lot of space, and they are pretty
much non-existent in the marketplace today.
3 color electron guns
An image is produced
on a CRT by using 3
color electron guns.
These colors are red,
blue, and green.
Which, when you
combine them, can
produce any color on
the color spectrum.
12
These guns shoot beams of electrons on the screen
and create an image that we see. These beams
repeatedly sweep across the face of the monitor, many
times per second. So it's constantly redrawing the
image that we see on the screen.
This redrawing of the
image is known as the
refresh rate. The refresh
rate is measured in hertz.
So for example, if the
refresh rate is 60 hertz,
and that means that the
beams sweep across the
entire face of the monitor,
redrawing the image at
The refresh rate is the
number of times per
the rate of 60 times per
second that a monitor
second. Now to the
redraws the image.
naked eye, most people
cannot detect this
because it does it so fast.
But a lot of times, some people complain of discomfort
in their eyes because they are noticing this constant
refreshing of the image. But this problem is usually
solved by increasing the refresh rate, which makes the
refreshing of the image less noticeable, which reduces
the amount of eye discomfort.
13
Inside CRT monitors is a metal plate called a shadow
mask. This metal plate can pick up outside external
magnetic fields, which can cause discoloration on the
screen, and because of this, CRT monitors need to be
degaussed.
Before a degauss
After a degauss
Degaussing is the process of getting rid of the
unwanted magnetic fields. Most CRTs do an
automatic degauss when the monitor is turned on, or
the monitor may have a button that you can press to
do a degauss.
Another type of monitors are
LCD, which stands for liquid
crystal display. LCD monitors
produce an image on a flat
surface by using liquid crystals.
Light shines through these
crystals to produce an image
on the screen, and it uses
LCD monitor
14
filters to produce different colors. LCDs were first used
in laptop computers. And now have made their way to
the desktop marketplace and have completely
replaced CRT monitors. They are lighter, thinner, use
less power, and take up less space than CRTs. LCDs
are also known as flat panel displays.
Modern LCDs use a technology called TFT, which
stands for thin-film-transistor. And as its name
implies, this technology uses a thin-film-transistor to
create a higher quality image, when compared to a
standard LCD, because each single pixel on the
screen has its own transistor. All LCDs sold today
have TFT technology.
In order for LCD monitors
to show an image on the
screen, it needs to have a
light source, and there are
a couple of different types
of backlighting that an
LCD monitor uses. One
Monitor with fluorescent
type of lighting is by using
lamp backlighting
fluorescent lamps.
These fluorescent lamps are the circular, glass, straight
tubing types, similar to regular fluorescent lamps that
we're all used to seeing. These lamps emit ultraviolet
light that's created when the mercury vapor inside the
lamp is ionized.
15
Another type of backlighting
that LCD monitors use is
LED. LED monitors use
multiple light emitting
diodes that are arranged in a
pattern that displays the
images on the screen. Now
this is a more modern form of
backlighting compared to
fluorescent lamp backlighting.
Most, if not all new LCDs, use
LED backlighting.
Monitor with LED
backlighting
Now both of these monitors are considered LCD
monitors, but the LCD that uses the LED backlighting, is
considered an LED monitor. So an LED monitor is just
an LCD monitor that uses LED backlighting.
Now there are two different types of LCD monitors that
you’re going to need to know for the exam.
And one of them is called TN. TN stands for twisted
nematic. This type of LCD monitor works by liquid
crystals actually twisting the light as it comes through.
TN is an older and cheaper technology that’s been
around for several decades. The viewing angle and the
color reproduction on a TN monitor are not as good as a
more modern LCD monitor. A TN monitor is often used
with calculators, digital watches, and older LCD
monitors.
16
A newer and more modern type of LCD monitor is IPS.
IPS stands for in-plane switching. This type of monitor
works by instead of the liquid crystals twisting, like in a
TN monitor, the liquid crystals stay in place and are
aligned in parallel with the glass. IPS LCDs use more
transistors than a TN monitor, so as a result, it does
consume more power. IPS was developed because of
the limitations of TN monitors, so as a result, IPS
monitors have better color reproduction and better
viewing angles.
Viewing angle
comparison
IPS monitor has a
better viewing angle,
compared to the TN
monitor.
TN monitor
IPS monitor
Resolution is defined as the
number of pixels that are
used to display an image on
the screen. For example, if a
monitor is set to a resolution
of 1280 x 720, then this
means that there are 1280
horizontal pixels, by 720
vertical pixels.
17
Which means that there are 921,600 pixels that are
being used. The higher the resolution, the higher the
number of pixels will be used. Which means a clearer
and sharper image. Depending on the hardware and
software being used, resolutions can be set anywhere
from 640 x 480, all the way up to ultra-high definition at
3840 x 2160. LCDs produce their best quality image
whey they are set to their highest resolution, which is
called their native resolution.
18
Printers
Printers allow the
ability to print copies of
documents and photos,
onto paper from a
computer. There are
several different ways
that a computer can
physically connect to a
printer, but the most
common way is by
using a USB cable.
This is known as a local connection because the
printer is directly connected to the computer. But you
can also connect a printer to a network if the printer
has a network interface, such as an Ethernet port or a
wireless network card. These are known as network
printers. Network printers are convenient because
they can be placed almost anywhere in a home or
office, as long as it's connected to the network (wired
or wireless). Another method of connecting is through
a network share.
Printer being shared over a network.
19
For example, you can allow other computers that are
on your network, connect to your local printer by
sharing your printer over the network. So after the
network share is complete, the other computers can
now print to the printer that is connected to your
computer. So your computer basically acts as a
gateway for other computers to access your printer.
But the drawback is that your computer has to be on in
order for others to use your printer.
There are several different types of printers. There are
non-impact printers and impact printers. Nonimpact printers print without striking an ink ribbon onto
paper, these include laser, inkjet, and thermal printers.
Impact printers are dot matrix printers, which will talk
about shortly.
Inkjet printers are the
most common printers that
are used for home use.
An inkjet printer works by
the print head moving
back and forth across the
paper during printing.
During this process, the
print head places ink on
the paper in very tiny
dots. In fact these dots
are so tiny that they are
smaller in diameter than a
human hair.
20
As these dots are precisely placed, they form to create
an image on paper.
Lower-end inkjet printers
typically come with two ink
cartridges, one is for color
and the other is for black.
Higher-end inkjets may
come with four ink
cartridges.
Inkjet printers are more affordable than laser printers
and they can produce photo quality results, but one of
the drawbacks is that the ink from an inkjet printer may
smudge, while ink from a laser printer does not
smudge.
Laser printers come in different sizes, from small
personal ones to larger ones for businesses. Laser
printers provide the highest quality print available
today and they are the most expensive.
21
A laser printer basically works by first placing an
electric charge on a rotating drum.
Rotating drum
Then a laser discharges a lower electrical charge on
the drum.
Laser drawing
image on drum.
So basically the laser draws the image that is going to
be printed, on the drum itself.
22
Then the drum is coated with a fine black powder,
known as toner. And as the drum is being coated, the
toner only clings to the areas where the laser has
drawn.
Black toner coating
the drum.
Then as the paper goes through the printer, the toner
is placed on the paper. And the result is a high-quality
print that is second to none.
Toner being placed
on paper.
23
Another non-impact printer
is called a thermal printer.
Thermal printers print by
using heat. They use a
special paper called
thermal paper, and on this
paper is wax-based ink.
When heat is applied to this
Thermal printer
paper, it turns black. So in
a thermal printer, the only
thing the print head does is
apply heat to the areas
where the ink should be
placed. Then when the ink
is cooled it becomes
permanent. And because
Wax-based thermal paper
of this technology, thermal
printers are very quiet.
Thermal printers are commonly used for printing
labels and barcodes.
Dot matrix printer
Dot Matrix printers are
almost non-existent today.
They are an old
technology that produced
mediocre print quality
when compared to laser or
inkjet printers. They are
also very noisy.
24
Dot matrix printers are impact
printers. The print head in a
dot matrix printer moves
across the paper, and as it
moves, the pins on the print
head strike against a cloth ink
ribbon which then comes in
direct contact with the paper,
producing each character in
the form of dots.
Prints characters in the
form of dots.
But despite being and outdated technology, dot matrix
printers can print multi-copy documents, such as
carbon copies. They are also very durable and last a
long time.
Printer Issues
Several issues can
happen when you're
printing. For example, if
you're printing something
and you see streaks, then
this could be a problem
with the ink cartridges in
an inkjet printer.
A lot of times the software that comes with the printer
will have a list of tools that you can use to clean the
print head. However, if the streaks are real bad, you
25
may have to remove the ink cartridges from the print
head and manually clean them with a lint-free cloth.
Another problem that
could happen, is when you
try to print something and
the image is faded or it's
completely blank. This
could also be a problem
with dirty ink cartridges, or
it could be that you're low
on ink or out of ink.
Ghosting is a problem
that can happen with laser
printers. Ghosting is
when you see a faint
image of a page you
previously printed and you
see the same image on a
newly printed page.
This is usually caused by the drum or the fuser. The
drum on a laser printer has a lifespan after so many
prints and then you have to replace it. So you can try
replacing the drum, but if you still see the same
problem after you replace the drum, then the problem
could be the fuser. If the problem is the fuser then
depending on what printer you have, you might need
to take the printer to a professional to get it fixed if
you’re not familiar with changing the fuser.
26
Paper jams are
another problem that
can happen with
printers. So if you try
to print something and
the paper doesn't
come out, then you
could have a paper
jam.
Old and worn out pick up
rollers could cause paper
jams and creases.
Paper jam
Paper jams could be caused
by debris inside the printer,
and debris inside the printer
could also be the reason
why the paper is coming
out creased. Paper jams
could also be caused by
faulty pick up rollers. This
typically happens with older
printers. When rollers wear
out, they tend to have
difficulty grabbing the paper
and feeding it through. So
in these cases, you might
want to inspect the rollers to
see if they need replacing,
or open up the printer and
check for any debris inside
the printer.
27
Another issue that could
happen, is that when you're
printing something and the
color may not print
correctly. Then all this
could be, is that one of your
color ink cartridges are
faulty, or they are low on ink
or even out of ink.
Be sure printer is turn
on and plugged in.
Check LCD for
messages.
Check for
connections on
network printers.
A lot of times when you try
to print something, and
nothing happens! Well
this could be a
connectivity issue.
Connectivity issues are
extremely common
especially when you're
dealing with network
printers. But the first
things to check are the
obvious ones. For
example, make sure the
printer is turned on.
Check for any errors on
the printer's LCD (if it has
one). If it's a network
printer with a wired
connection, make sure
28
the network cable is connected. You should always
check the obvious things first before diving into the more
complicated issues, such as checking if the network
printer has an IP address.
Virtual Printing
Instead of printing a document unto physical paper. You
can also print your document and store it on your
computer in a digital form. This is called virtual
printing. Virtual printing is done for several reasons,
and one of those reasons is called print to file.
Printing a document to a file, saves the document in a
format that another printer can print. So for example, if
you wanted to print something and you don't have a
printer, you can use the print to file feature and it will
save the document in an uneditable digital form that can
be sent to another computer that has a printer, and then
that computer can print the file for you.
Another form of virtual printing is called print to PDF.
PDF stands for portable document format.
29
Printing a file to PDF prints a virtual document into a format
that's universally readable across all devices such as
computers, tablets, and smartphones.
Word document
converted
(printed) to a
PDF
Word document
PDF
This is because the PDF format is so common, that just
about every new device on the market will be able to
read a PDF file without adding any additional software.
But older devices may need additional software installed
in order to read a PDF document. The most common
PDF reader software is Adobe Acrobat Reader, which is
available free to download.
30
Storage Devices
A computer has basically two
types of memory: primary
memory and secondary
memory. Now primary
memory is temporary, which
we'll talk about later, but
secondary memory is
permanent, and this deals
with the hard disk drive. The
Hard drive
hard disk drive is a sealed
case that contains magnetic
disks. These disks is where the actual data is stored on.
These disks rotate at high speeds, and as they do, the
actuator arm will either write data to the disks or read data
from the disks, depending upon what the user wants to
do. These magnetic disks can rotate at speeds of either
5,400, 7,200, or 10,000 RPM. The typical hard drive
that's used today in a desktop operates at 7,200 RPM. A
cheaper desktop hard drive operates at the 5,400 RPM
range, which is also the speed of a typical laptop hard
drive. Higher-end hard drives would operate at the
10,000 RPM range. However, these higher-end hard
drives are not commonly used anymore, because of the
advanced speeds of solid state drives. And hard drives
are considered non-volatile because they can retain and
store data when not connected to a power source.
31
SATA cable
Hard drives today use the
Serial ATA interface. Now,
this is a newer standard that
is faster than the old parallel
ATA interface. Instead of
data traveling in a parallel
path, the data travels and a
serial path. Which means
that data travels one bit at a
time. SATA drives have
transfer speeds averaging 6
Gbit/s, which is considerably
faster than the old parallel
ATA. Other advantages of
SATA drives are that they are
hot-swappable, and the
cables are a lot smaller,
which makes cable
management a lot easier.
Another type of storage
device is an SSD or solid
state drive. These drives
have no moving parts. These
drives use flash memory
chips to store data, and since
it has no moving parts, the
data transfer is very fast.
SSD drive
32
There are also drives out there that combine the use of
magnetic disks and flash memory. These are called
hybrid drives. Hybrid drives take advantage of the
large capacity and the low cost of magnetic disks, with
the speed of an SSD. In a hybrid drive, the magnetic
disks will be used to store data, while the flash memory
would be used for the caching of the data. Hybrid drives
are primarily used where cost is an issue, because SSD
drives are considerably more expensive than magnetic
hard drives.
Hybrid drives use both magnetic disks
and flash memory.
Removable storage is both
convenient and portable
because these types of
storage are not stored
internally in a computer,
they are attached from the
outside. So for example a
tape drive.
33
A tape drive is an inexpensive way to backup data from
your hard drive. It attaches to a computer, usually with a
USB cable, and then the data is backed up sequentially
to tape. Which basically means that if you ever have to
restore the data, you have to restore the data in the
same order as you backed it up.
CD-ROM drives have become a standard component in
computers today (but not for long). It's a device that
reads data from a CD-ROM, which is a disc that stores
permanent data. CD-ROM stands for compact disc
read-only memory, which means that the data can only
be read and cannot be changed or written to.
CD-RW stands for
compact disc re-writable.
A CD-RW drive can
change or write data to a
CD. It has a moving laser
assembly that writes or
burns the data to a CD.
Now, there are two
different kinds of CDs that
can be written to: a CD-R,
which stands for a CD
recordable, or a CD-RW,
A laser from a CD-RW drive,
writing data to a CD.
34
which stands for a CD re-writable. A CD-R can only
be written once to, but a CD-RW allows data to be
rewritten multiple times. And CD-ROMs hold
approximately 700 megabytes of data.
DVD-ROM drive is a
device that reads DVD
discs. The DVD drive
has largely replaced
ordinary CD-ROM drives
because of the larger
storage capacity of DVD
discs. A DVD can store
approximately 4.7 GB of
data. And all DVD
drives today can read
both DVDs and CDROMs.
Just like a CD-RW drive,
there is also a DVD-RW
drive. A DVD-RW drive
can change or write data
onto a DVD. It can write
data onto DVD-R discs
and rewrite data onto
DVD-RW discs.
Some DVD burners have the capability of burning duallayer DVDs. These are called DVD-RW DL drives. Duallayer DVDs have two recordable layers. So they can
35
store twice the amount of data than a regular DVD. Duallayer DVDs can hold approximately 8.5 gigs of data.
A dual layer DVD can hold
twice the amount of data as a
standard DVD. Approx. 8.5
GB
Blu-ray drive
Blu-ray is the latest
optical drive to date that
was released in 2006.
Blu-ray will eventually
replace the DVD format
because of its high
capacity. Blu-ray uses a
shorter wavelength laser
compared to DVD, which
allows a Blu-ray disk to
store far more data than
a DVD. A standard Bluray disc can hold 25 GB
of data, which is 5 times
more than a DVD.
Blu-ray disc
Now just like CD and DVD recordable drives, Blu-ray also
has a recordable drive, and this is called a BD-R or Blue
Ray disc recordable drive.
36
A BD-R drive is where you can burn data to a Blu-ray
disc, one time. Or you can also erase data or overwrite
the data on a Blu-ray disc using a BD-RE or Blu-ray
recordable erasable drive. So as stated before
standard single-sided Blu-ray discs hold 25 gigabytes of
data, or there's also Blu-ray double sided discs which
hold 50 gigabytes of data.
An external hard drive is a
hard drive that's enclosed in a
case. It's a portable hard drive
that can be externally attached
to any computer typically using
a USB cable. External hard
drives are primarily used to
backup data from a computer's
internal hard drive, to prevent
data loss.
USB flash drive - also
known as a thumb drive.
External hard drive
Another type of removable
storage is what's known as a
solid state disk. Now, these
have no moving parts. This type
of memory uses memory chips
to store data. These include
USB flash drives. A USB flash
drive is a miniature storage
device with a USB interface.
These drives can store
anywhere from 250 MB - 128
GB, and their size is small
37
enough to fit on a keychain. They are a fast and
convenient way to store data on the go.
Secure digital or SD cards are a
popular type of flash memory. These
are primarily used in digital cameras
for storing photographs and videos.
Then, these photographs and videos
can then be easily transferred to a
computer using an SD card reader
interface. SD cards come in various
capacities, anywhere from 2 GB up to
512 GB.
Other types of SD cards include the mini SD and the
micro SD, and you can see the comparison of the
different sizes below. While the standard SD card is
used for storage in digital cameras, the micro SD card
is what’s commonly used in most smartphones for
adding extra storage.
SD
Mini SD
Micro SD
Another type of flash drive that is commonly used in a
lot of DSLR cameras is compact flash. Compact flash
cards provide quick and easy storage for pictures and
38
videos in DSLR cameras. And then, they can be easily
transferred to a computer using a card reader.
Compact flash card
Commonly used in
DSLR cameras.
A type of non-standard SD
card would be the older XD
picture card, where XD stands
for extreme digital. This was
a type that was proprietary in
Olympus and Fujifilm
cameras.
xD picture card
The kind of memory that you
would typically find inside
smartphones and tablets is
called eMMC. eMMC stands
for embedded multimedia controller. eMMC
consists of putting flash
memory and a flash memory
controller into one package.
So this is the tablet’s or
smartphone’s internal or
embedded memory, and not
external storage like an SD
card.
39
Power Supply
The power supply is a device
that supplies power to the
computer. It's a square metal
box with a bunch of wires
emerging from one end that
fits inside the computer case.
The power supply is usually
Power supply
located at the very top or the
bottom of a standard tower
case. The power supply converts 110 volt AC current
into the specific voltages that the computer needs.
The most common form factor that a power supply
comes in, is ATX.
A power supply is equipped
with different types of
connectors. One type is
called the P1 connector.
This is the main power
connector that connects
directly into the motherboard
and provides it with power.
The P1 connector has either
20 or 24 pins.
P1 connector will
have 20 or 24 pins.
Another type of connector is called the P4. This is a 4
pin connector that also connects into the motherboard.
40
The P4's purpose is to supply
power to the CPU. This connector
is used with modern motherboards.
P4 connector
Another type is called molex. The
molex connector is a 4 pin
connector that connects disk
drives, such as hard drives, and
CD and DVD-ROM drives.
SATA connector
There is also a SATA
connector. This is a 15 pin
connector, that is used to
connect disk and optical
drives that have a serial ATA
power connection.
Another connector is called the 4
pin BERG connector or mini
connector. This is a small
connector that is used to supply
power to the floppy drive.
6 pin connector
(also comes in 8 pin)
Molex
4 pin BERG
Finally, there's the 6 pin or 8
pin connector, and this is
used to supply power to
certain PCI-E video cards.
41
Motherboard
The motherboard is the main component of a
computer. It's basically a large circuit board where all
the computer components connect to, such as the CPU
socket. The CPU socket is where the CPU or central
processing unit is placed. There's also the memory
slots, and this is where the primary memory modules,
known as RAM, are inserted. There is also the bus
slots. The bus lots are used to install various
components to add more capabilities to a computer,
such as a video card, sound card, network card, and so
on.
CPU
socket
RAM
(memory)
slots
Bus
slots
Motherboard
42
Motherboards come in different shapes and sizes,
known as a form factor.
The most common form
factor motherboard that is
used in PCs today is ATX.
ATX stands for advanced
technology extended. It
was created in 1995 and is
now the de facto standard
form factor for PCs today.
A full-size ATX motherboard
is 12 x 9.6 inches.
Prior to the development of
ATX, was the AT form
factor. AT stands for
advanced technology.
This was used in the 1980s
that was developed by IBM.
AT motherboards are 12 x
13.8 inches in size, and
they're no longer in
development since the
succession of ATX.
Another version of the ATX
motherboard is the Micro
ATX. The micro ATX
motherboards are smaller
than ATX boards, as its
name suggests. Micro ATX
43
boards are 9.6 by 9.6 inches. It's a square design,
compared to the standard rectangular design of the ATX.
They're cheaper than ATX boards and were designed to
fit in smaller computer cases. They also have fewer
features and consume less power than a standard ATX
board.
The BTX form factor was
designed by Intel to make
further improvements from
the ATX form factor; such
as an improved board
design, which creates a
more inline air flow, which
improves cooling.
For example notice how the memory and bus lots are
horizontal, flowing with the direction of airflow, instead of
inhibiting it, compared to the ATX form factor. Another
improvement is the structure design, which is flexible
enough to work on both smaller cases and larger tower
cases.
Another form factor is the
NLX. NLX was created by
Intel, and it was designed
for low-end, low profile
computers. Instead of
expansion cards that plug
perpendicular into the
motherboard, the NLX
board use a riser card
NLX board with riser
card installed
44
for expansion cards, so they can plug in parallel with the
motherboard. You would typically find NLX boards in
slimline computer cases.
Even smaller than Micro ATX
and BTX motherboards, there
is the ITX form factor. The
ITX form factor came out in
2001, starting with the MiniITX. This was designed for
the ever-increasing demand
for smaller, space saving
computers.
Mini ITX
The ITX standard consumes less power, and because it
uses less power, they are often cooled only by using heat
sinks and not with fans. ITX was developed by VIA
Technologies, and there are currently four sizes that are
in the ITX form factor.
Nano-ITX
Pico-ITX
There's the Mini-ITX (above).
There is also the Nano-ITX
which came out in 2005, and
this was designed to be used in
devices such as digital video
recorders, media centers, and
cars. Then there's also the
Pico-ITX which came out in
2007. And in 2009, VIA
Technologies introduced the
45
6 cm
6 cm
Mobile-ITX
smallest x86 CPU module
specification in the industry,
with the release of the
mobile-ITX. The mobile-ITX
measures 6 cm x 6 cm and it
was designed to provide
developers with a
standardized and ultracompact specification for
building new computer based
products.
Motherboard
I/O INTERFACES
Motherboards come built with several input-output
interfaces these interfaces are largely located on the
rear input-output panel of the motherboard.
Motherboard I/O panel
For example, the PS/2 connector. The PS/2 connector
is a 6-pin, mini-DIN connector. A motherboard would
typically have one or two of these and are usually
located towards the top of the motherboard.
46
PS/2 connectors
One connector is for plugging in the mouse, this is the
green PS/2 connector. The other is for plugging in the
keyboard, which is the purple connector. But PS/2
connectors are an older technology and is slowly being
phased out in favor of a USB port.
USB ports
The most common interface on a motherboard is the
USB port. USB stands for universal serial bus, and
motherboards would typically have several USB ports
because there are so many different peripherals that
utilize the USB interface, such as keyboards, mice,
cameras, external drives, and printers. In addition to
connectivity, the USB port also supplies electric power
to that specific peripheral. Some USB ports are
mounted on the rear input-output panel and some are
located directly on the surface of the motherboard.
The first USB interface was USB 1.0 in 1996. The
transfer speed was 1.5 Mbit/s. USB 1.1 was
introduced in 1998, with a transfer speed of 12
Mbit/s. USB 2.0 came out in 2001, with a transfer
47
speed of 480 Mbit/s. The latest version is USB 3.0,
with data transfer speeds of up to 5 Gbit/s.
Serial port
Another interface that can be found in older
motherboards is the serial port. The term serial refers
to sending data one bit at a time. The serial port is an
older technology interface which is rarely seen on new
motherboards today. Back then, this was mainly used
for connecting terminals and modems to computers, but
now it has been widely replaced by the faster USB
interface. The most common interface of a serial port is
the RS-232 standard, which uses the common "D"
connector such as the DB-9.
Parallel port
The parallel port is another interface that could be
found on a motherboard's I/O panel. It was mainly
used for connecting printers, and like the serial port, it is
also being phased out (pretty much gone) and replaced
by the faster performance of the USB port. It uses a
wide D-sub connector known as the DB-25. And unlike
serial ports, that send data one bit at a time, a parallel
48
port sends data signals simultaneously over several
parallel channels.
Integrated video adapter
A video adapter is another interface that could appear
on the motherboard. Now, I say it could appear,
because some motherboards have a video adapter and
some don't. But the motherboards that do have a video
adapter, then this is known as integrated video,
because the video adapter and the motherboard are
essentially one unit. The video adapter is what
generates images from your computer to your monitor.
The most common kind of port on an integrated video
adapter is VGA, which stands for video graphics
array. The VGA port carries analog data. It has 15
pins divided into 3 rows and usually has a blue color.
VGA video adapter
Integrated video adapters are usually not very powerful.
They are good for normal everyday use with light
applications, but when used for extensive graphic
applications such as gaming, they can fall short.
49
That's why a lot of people will bypass the integrated
video and add an expansion video card that has
enough power to suit their needs.
Expansion video card
Firewire port
The IEEE 1394 connector is commonly known as
firewire. Firewire is recognized by its "D" shape, and is
commonly used to attach devices such as digital
cameras and printers. It's very similar to a USB port.
Firewire and USB are both used to attach peripherals
and they both have similar transfer speeds, but firewire
is not nearly as popular as USB. That's why on a
modern motherboard today, there might not be any
firewire ports, or if there are, you might find one or two.
Firewire has a transfer speed or 400 Mbit/s.
The NIC or network interface card is a port on the
motherboard that is used for networking purposes, such
as connecting to the internet and sharing data between
50
NIC port
computers. The port is designed
for an Ethernet cable with an
attached RJ-45 connector. A
NIC provides a computer with a
constant dedicated connection to
a network. Every NIC has its
own unique identifier, called a
MAC address. The transfer
speed ranges from 10 - 1000
Mbit/s.
RJ-45
connector
Integrated sound port
A sound card is another type of interface that could be
found on a motherboard. And just like integrated
video, if I motherboard has a sound card built-in, then
this is known as integrated sound. A sound card is
what processes audio through the computer's
speakers. A basic sound card has an audio output
port for attaching speakers, and an import port for a
51
microphone for recording purposes. More
sophisticated sound cards will have extra ports. For
example, for subwoofers, surround sound, and ports for
other digital audio equipment.
eSATA port
Some motherboards have a SATA port on the rear I/O
panel. This is known as eSATA or external SATA.
It's used for attaching an external SATA device to a
computer, such as an external SATA hard drive. It
functions similar to USB and firewire, but the transfer
speed is faster. The disadvantage it has compared to
USB and firewire, is that eSATA requires a separate
power plug to supply the drive with power. However,
there is a new SATA port called eSATAp, which is
power over eSATA. This port combines data transfer
and power in an all-in-one port, similar to USB and
firewire.
52
Adapter/ Expansion Cards
Adapter cards or expansion cards are circuit boards
that can be installed into the expansion slots on a
computer's motherboard. These adapter cards are
installed to increase the functionality of the computer.
Some examples of expansion cards are video cards,
audio cards, and storage cards.
Motherboard with 2 adapter
cards installed.
One of the most common adapter cards is a video
card. A video card is what generates images from your
computer to your monitor. A typical video card is a
printed circuit board that directly attaches to the
computer's motherboard. Video cards are also known
as graphics cards and graphics adapters.
Video card
53
A video card has several key components, such as a
graphics processor unit or GPU, memory chips, a bus
type, and video ports. The way video is transferred
from the video card to the monitor is through the video
GPU
ports.
Memory
Video ports
Bus type
There are several different types of video ports that are
used today. One port is called S-Video or separate
video or also known as super video. S-Video is an
analog transmitter. It transmits two signals over one
cable. One signal is for color and the other signal is for
brightness. The S-Video port is round and is usually a
black color.
S-Video
Another port is called VGA, which stands for video
graphics array. The VGA port is an older technology
that was developed in 1987. The VGA port has 15 pins
54
divided into three rows and usually has a blue color.
The VGA port carries analog data.
VGA port
Another video port is called a digital visual interface or
DVI. This is a newer technology designed to succeed
the older VGA port. It was developed in 1999 and it was
designed to provide uncompressed high-quality video to
LCD monitors.
DVI port
DVI-A
DVI-D (single link)
Now there are three different
versions of the DVI cable
standards. There's DVI-A, where
the A stands for analog. This is
used to send only analog signals.
There's DVI-D, where the D
stands for digital. This is used to
send only digital signals.
DVI-D (dual link)
55
DVI-I (single link)
There's also the DVI-I, where
the I stands for integrated. This
is used to send both analog and
digital signals.
DVI-I (dual link)
Now on the connectors that are able to send digital
signals, which would be the DVI-D and DVI-I, there are
two different options in the DVI standard. There is
single link and dual link. The difference is, that dual
link has six extra pins, and these pins are what allows
for a higher resolution than single link cables.
Another type of video port is called HDMI, which
stands for a high definition multimedia interface.
HDMI was developed in 2002 and it was designed for
transmitting uncompressed video and audio digital
data through a single cable. HDMI is one of the best
standards for high definition in consumer electronics,
delivering crystal clear video, as well as audio.
HDMI port
And there is also the DisplayPort. The DisplayPort
debuted in 2006 and it was developed by VESA, which
stands for the video electronics standard association.
56
The DisplayPort was primarily designed to be used for
video, but in addition to video, it can also be used to
carry USB and audio data as well. It's a highperformance interface that is meant to replace the
older VGA and DVI interfaces. And it can also connect
using adapters to the older DVI, VGA, and HDMI ports.
DisplayPort
The sound card is another type of adapter card that
processes audio through the computer speakers. A
sound card attaches into the computer's motherboard
through a bus slot. A basic sound card has an audio
output port for attaching speakers and an input port
for a microphone for recording purposes. More
sophisticated sound cards have extra ports for
example ports for subwoofers and surround sound.
Sound card
57
Some people have video capture cards installed on
their computer. These cards allow a user to capture
analog video, such as from a video camera. Then it will
convert it to a digital form and then it can be stored on
their computer's hard drive.
Video capture card
TV tuner cards allow signals from a television to be
picked up by a computer. So you can not only watch TV
from your computer, but you can also record TV
programs and then store them digitally in your
computer. In fact, a lot of TV tuner cards also act as a
video capture card.
TV tuner card
60
A wireless network card does the same thing that a
wired card does, except that a wireless card does not
use a cable. It instead uses a wireless connection. It
has a built-in antenna that is used to wirelessly connect
to a network. Now, this is very convenient for computers
and devices that have a wireless network card because
they can be placed anywhere in different locations in a
home or office without the hassle of messing with
cables.
Wireless
network card
61
RAM (memory) Slots
RAM or random access memory is temporary
storage memory that's installed on the motherboard in
the memory slots.
Memory slots
The motherboard can have a various number of
memory slots. The average motherboard will have
between two and four slots. Memory slots come in
different types depending upon what type of RAM it
accepts.
RAM DIMM
For example, most motherboards accept DIMMs
because it's the most common type to date. DIMM
stands for dual inline memory module. A DIMM has
168, 184, 240, or 288 pins. A DIMM is a dual inline
module because it has two independent rows of these
62
pins - one row on each side. DIMMs will also have a
64-bit data path (which we will discuss shortly).
There is also the SIMM, which stands for single inline
memory module. SIMMs are an older technology and
are not produced anymore. SIMMs with either have 32
or 72 pins, and they have a 32 bit data path.
SIMM
The term 32 or 64 bit data path, refers to the number of
bits of data that are transferred in one cycle. The more
bits that are transferred in one cycle, the faster the
computer will be. A single bit or one bit of data is the
smallest form of data that the computer reads.
Because in the computing world, a computer only
understands ones and zeros, which is represented by
a single bit of data.
Now there's also the term byte, and 8 bits = 1 byte.
So if a memory DIMM is rated to have a 64 bit data
path, then that means that it has an 8 byte wide data
path or bus, because 64 / 8 = 8. If a memory SIMM
that is rated to have a 32-bit data path, then that
means that it has a 4 byte wide bus, because 32 / 8 =
4. So that's why DIMMS are faster than SIMMS. Now
this information will be useful in an upcoming lesson on
how we determine the exact bandwidth (speed) of
memory modules.
63
RAM
In a previous section, we talked about secondary
memory, which is permanent storage. This dealt with
hard drives. Now we're going to talk about primary
memory or temporary storage, and this is called RAM.
RAM stands for random access memory. In order for
data or a program to run, it needs to be loaded into
RAM first.
So here is how it works. The data or program is stored
on the hard drive. Then from the hard drive, it is
loaded into RAM.
Data from the hard drive is
being loaded in to RAM.
Once the data is loaded into RAM, the CPU can now
access the data or run the program.
64
Once the data is in RAM,
the CPU can now access it.
Now a lot of times if the RAM (memory) is too low, it
might not be able to hold all the data that the CPU
needs. So when this happens, then some of the data
has to be kept on the slower hard drive to compensate
for low memory.
Fro
mR
AM
t
CPU o the
HD
e
th M
om RA
r
F
to
So instead of data going from RAM to the CPU, it has
to do extra work by going back to the hard drive, and
when this happens it slows down the computer. So to
65
solve this problem, all you need to do is increase the
amount of RAM on the computer. And by increasing
the memory, all the data can be loaded into RAM
without the need of constantly accessing the hard
drive. Therefore the result is a faster performing
computer.
RAM requires constant electrical power to store data
and if the power is turned off, then the data is erased.
RAM is stored on the motherboard in modules that are
called DIMMs, and these DIMMs come in different
memory sizes. Today they range anywhere from
128MB - 64GB of memory per DIMM.
RAM also comes in different types, such as dynamic
RAM or DRAM. DRAM is memory that contains
capacitors. A capacitor is like a small bucket that
stores electricity, and it's in
these capacitors that hold the
bit of information, such as a
one or a zero. Because that's
how computers read data,
which are ones or zeros. And
because DRAM has
capacitors, they have to be
refreshed with electricity
Capacitor
constantly, because capacitors
do not hold a charge for very
66
long, they constantly leak. And this refreshing of
electricity is where we get the name dynamic. The
capacitors have to be dynamically refreshed often
otherwise they will forget the information that they're
holding.
SRAM stands for static RAM. This memory uses
transistors instead of capacitors, so it does not have to
be refreshed unlike DRAM. Therefore it is much faster
than DRAM, but it's also very expensive. An example
SRAM would be the memory cache levels that are
used by the CPU.
Another type of memory is called SDRAM, which
stands for synchronous DRAM. This type of memory
is what is used today in RAM DIMMs. The difference
between SDRAM and DRAM, is basically speed. The
older DRAM technology operates asynchronously with
the system clock, which basically means that it runs
slower than the system clock, because its signals are
not coordinated with it. However SDRAM runs in sync
with the system clock, which is why it is faster than
DRAM. All the signals are tied to the system clock for
a better controlled timing.
DRAM - Dynamic RAM - Operates
asynchronously with the system clock.
SDRAM - Synchronous DRAM - Operates
synchronously with the system clock.
67
SDRAM is rated at different speeds. For example, a
stick of old SDRAM, way back in the 1990's, could be
labeled PC-100. The 100 equals the speed at which it
operates, which is 100 MHz. And since SDRAM only
comes in 64 bit modules, it has an 8 byte wide bus,
because 64 / 8 = 8. So to figure out the total
bandwidth (speed) of PC-100, you multiply 100 MHz x
8 bytes which equals 800 MB/s. So the total
bandwidth of PC-100 = 800 MB/s.
PC-100
100 MHz = The speed at which it operates.
8 byte wide bus.
100 MHz x 8 bytes = 800 MB/s
So an SDRAM module labeled PC-133, you multiply
133 x 8 which equals 1066. So the total bandwidth for
PC-133 = 1066 MB/s.
68
As technology increased and processor and bus
speeds have gotten faster. A new RAM technology
was developed to keep up with a faster speeds of
computers. This newer technology is called DDR,
which stands for double data rate; and that's basically
what DDR does. DDR sends double the amount of
data on each clock signal, when compared to non DDR
RAM. Non DDR, or single data rate RAM, uses only
the rising edge of the signal to transfer data. However
DDR uses both the rising and falling edges of the clock
signal to send data. Which makes DDR twice as fast.
non DDR
DDR
DDR uses both the rising and falling edges of the
clock signal to send data.
DDR is also labeled differently than non DDR RAM.
Instead of including the clock speed in its name, like PC133, where 133 equals the clock speed, DDR uses the
total bandwidth instead. For example a DDR DIMM
labeled PC-2700, the 2700 is not the clock speed, but it's
the actual total bandwidth. The clock speed for PC-2700
69
is 333 MHz. So 333 MHz x 8 bytes is rounded off to
2700 MB/s, which is where we get the name PC-2700.
DDR uses the total bandwidth in its name.
PC-2700
333 MHz = the speed at which it operates.
8 byte wide bus.
333 MHz x 8 bytes = 2700 MB/s
Another example is PC-3200. PC-3200 has a clock
speed of 400 MHz. So 400 MHz x 8 bytes = 3200 MB/s,
which is where we get the name PC-3200.
A new technology that has succeeded DDR is DDR2.
DDR2 is faster than DDR because it allows for higher
bus speeds, and it also uses less power than DDR. A
DDR2 DIMM has 240 pins, compared to 184 pins on
DDR. Some examples of DDR2 are PC2-3200 and
PC2-4200.
DDR2 DIMM
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An even newer technology is called DDR3. DDR3 is
twice as fast as DDR2, with a bandwidth of over 12800
MB/s. Like DDR, a DDR3 DIMM also has 240 pins, but
the notches in the DIMMs are in different places. So
you can't put a DDR3 DIMM in a RAM slot made for
DDR2. Motherboards are made to support a certain
type of memory, so you can't mix DDR, DDR2, or DDR3
on the same motherboard. Some examples of DDR3
are PC3-8500 and PC3-12800.
DDR3 DIMM
To meet the higher demands of faster processors and
memory controllers, a new technology was developed
called dual channel mode.
Dual channel mode
requires a pair of
identical DIMMs
installed on the
motherboard,
which allows the
Dual channel memory slots
memory controller
the ability to communicate with 2 DIMMs
simultaneously. Therefore increasing the speed of
accessing the memory. In order for dual channel
mode to work, the motherboard must be equipped to
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work with dual channel mode. The memory DIMMs
must also be identical to each other in speed, size, and
features. Then the DIMMs must be inserted into the
motherboard in a specific slot configuration in order to
enable dual channel mode. Typically the memory slots
will be color-coded to help assist in identifying where
they should be inserted. For example, above we have
some dual channel memory slots. So in order for dual
channel mode to work, you need to install a pair of
identical DIMMs in the slots of the same color. In this
case we put a pair of DIMMs in the yellow slots.
2 DIMMs installed in the yellow slots. Dual channel mode
is now enabled.
There is also a triple channel mode. Triple channel
mode is not very common and very few motherboards
offer this feature. Triple channel mode allows the
memory controller the ability to communicate with 3
DIMMs at the same time. In modern computers,
motherboards have a 64-bit architecture. So in single
channel mode, it can transfer 64 bits of data at a time.
In dual channel mode, that is doubled to 128 bits at a
time. In triple channel mode, it's tripled to 192 bits at a
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time. So as stated before, triple channel mode is only
available on a few motherboards and only certain Intel
Core i7 processors support triple channel mode. So
here is an example of a
triple channel capable
motherboard. On this
motherboard there are
six memory slots with
two different colors. So
if you're going to install
three DIMMs on this
motherboard, you must
put the DIMMs in the
same color-coded slots
in order to utilize triple
Triple channel equipped
channel mode. Those
memory slots.
DIMMs must also be
identical to each other.
The term single sided or double sided RAM doesn't
necessarily refer to the physical location of the memory
chips that are on the sides of the memory module.
Top view of DIMMs showing memory chips.
It instead refers to the groups of memory chips that a
memory controller accesses. So for example, double
sided RAM has two groups of memory chips. Now, this
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doesn't mean that the memory chips are physically
located on both sides of the memory module. Now,
they can be on both sides of the memory module, or
they can only be on just one side. But that's not what
double sided means. Double sided means that the
memory controller sees these two groups of memory
chips separately, and it can only access them one
group at a time.
Single sided RAM has one group of memory chips.
These chips can be physically located either on one
side or both sides of the memory module, but that's not
the point. The point is, that because it's single sided
RAM, the memory controller can access it as one
group. Therefore since it's one sided, or one group,
the memory controller can access it as one group,
which makes single sided RAM faster than double
sided RAM.
Some RAM modules have ECC, which stands for
error correcting code. ECC detects if the data was
correctly processed by the memory module, and
makes a correction if it needs to. You can tell if a
RAM module has ECC by counting the number of
memory chips on the module.
non ECC
8 chips
ECC
9 chips
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In a standard non ECC DIMM, it will have eight
memory chips, but in an ECC module, it will have nine
memory chips. Most RAM modules today are non
ECC, and this is because of the advancing technology
that has minimize memory errors and has made non
ECC RAM more stable. Typically today, ECC memory
is mostly used in servers, because servers need to be
up and running at all times, and using ECC memory is
just an extra precaution to guard against any memory
errors.
There is also buffered and unbuffered RAM. Now
buffered RAM, which is also called registered RAM, is
made to add stability to RAM. Buffered RAM adds an
extra register between the RAM and the memory
controller. The extra register stores data, or buffers the
data, before it gets sent to the CPU. This is what adds
stability and reliability in computer systems that have a
lot of memory modules installed. So it's basically used
to lessen the electrical load on the memory controller,
that’s produced when a computer uses a lot of memory
modules, for example in servers.
The kind of RAM that is used in smaller devices, such
as laptops, is called SODIMM. SODIMM stands for
small outline dual inline memory module.
SODIMM
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SODIMMs are roughly half the size of regular DIMMs,
and like DIMMs, that are used in desktops, SODIMMs
also come in different types, such as DDR and DDR2
and DDR3. So if you plan on adding RAM to your
laptop, you need to make sure you install the correct
kind, because the different levels of DDR in SODIMMs
are not compatible with each other.
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Cooling
Cooling is very important to a
computer. Computers
generate a lot of heat and if
the components of the
computer are not adequately
cooled, the computer will
overheat. If the computer
overheats, the computer could
run slow, lock up, or shut
down. It will also eventually shorten the life of the
computer because heat is an enemy to a computer's
longevity. Two of the biggest heat generators come
from the CPU and the video card.
So the main way to adequately cool the computer is
with case fans.
Exhaust
fan
Intake
fan
Case fans inside a tower computer case.
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Case fans are mounted inside the computer case. A
basic case fan setup will include at least two fans. The
fan that is mounted in the front of the computer case,
is the intake fan. The intake fan is for drawing cool air
from outside the case, to inside the case. The other
fan is the exhaust fan, which is located in the back of
the case. The exhaust fan is designed to push warm
air outside the case. Once these fans are in place,
they are designed to work with each other to create a
constant flow of cool air coming into the computer, to
cool the computer components.
Warm air
Cool air
Case fans creating a constant flow of cool air.
So the cool air comes in and cools the computer
components. Then as the air makes contact with the
hot components, the air naturally gets warmer, and is
then drawn outside the case. Then the cycle starts all
over again to create a constant circulation. This type of
cooling is known as active cooling.
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The biggest heat
generator in the computer
is the CPU. The CPU is
the brain of the computer,
and it produces an
enormous amount of heat
in a very short amount of
time. In fact, if the CPU
were to run by itself
The CPU is the biggest
without
any
extra
cooling
heat generator.
components, the CPU
would likely fry itself within 10 seconds (trust me, I
tried it). So to remedy this problem, a CPU needs a
heat sink to help dissipate the heat. A heat sink is
basically an aluminum block with fins that directly
makes contact with the CPU.
The heat sink's purpose is
to increase the surface
area of the CPU so that it
can make more air contact
for cooling. The larger the
heat sink, the larger the
surface area will be,
therefore increasing the
Heat sink
cooling ability.
The fins on the heat sink are designed to further
increase the surface area for air circulation. Once the
heat sink makes contact with the CPU, the heat will
transfer from the CPU to the heat sink, where the air
can cool the heat sink, which will cool the CPU. This
type of cooling is known as passive cooling.
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The heat sink fins are designed to further increase the
surface area for air circulation.
It's important that the heat sink and the
CPU make the most contact with each
other so that adequate cooling can
take place. So that's why it's important
to apply thermal compound on the
CPU before attaching the heat sink.
Thermal
compound
being applied
on a CPU.
Thermal compound is used to fill in the microscopic air
gaps between the heat sink and the CPU, to make up
for the imperfections of the flat surfaces. The surface
areas between the CPU and heat sink are flat, but
they are not perfectly flat when examined with a
microscope.
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Magnified
Microscope reveals air gaps. The surfaces
are not perfectly flat.
Thermal compound is designed to fill in the
microscopic air gaps so the most contact can be made
between the heat sink and CPU.
Magnified
After thermal paste is applied. It fills in the
microscopic air gaps.
Another type of cooling is water cooling. Instead of
using air, this type of cooling uses water to cool the
computer components. For example, here is a water
cooling unit for the CPU. There is a pump, hosing,
and a radiator.
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Hosing
Radiator
Pump
CPU water cooler
Inside this unit is water. The unit is placed directly on
top of the CPU just like a traditional heat sink and the
pump inside constantly circulates the water throughout
the entire unit to keep the CPU cool. Once the water
reaches the radiator, the water is air cooled by a
radiator mounted fan that draws air into the radiator
and cools the water. Then the cycle is repeated, so a
constant flow of cool water makes contact with the
CPU. So as a result, water cooling units, cool
components far better than air cooling. They are also
much quieter, but at the same time, water coolers are
more expensive.
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CPU, Socket, &
Chipset
The CPU socket is the place on the motherboard
where the CPU is placed. The socket is a square
plastic or metal holder with multiple holes to
accommodate the pins on the bottom of the CPU.
CPU
Socket
As these holes and pins make contact, they provide
physical and electrical contact between the
motherboard and the CPU.
A modern CPU socket is called a ZIF, which stands
for zero insertion force, which basically means that
the CPU is installed in the socket with no force.
The CPU just drops in the
socket easily. There are
different types of CPU socket
designs called packages.
One of the most common
types of these packages is
ZIF socket
the PGA or pin grid array.
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The PGA package is a typical square design with
holes and a lock down lever.
LGA socket
The latest in socket design
packages is called LGA, which
stands for land grid array.
The LGA socket is a metal
casing with a door that closes
over the CPU, and locks down
with a lever. Unlike previous
socket versions, which have
holes, the LGA has pins that
make contact with the bottom
of the processor. LGA
processors don't have pins,
instead they have pads that
rest on the LGA socket pins.
For the CompTIA A+ exam, you're going to need to
know certain characteristics of several socket types.
These socket types are categorized by two different
brands. These brands are Intel and AMD.
So starting with the Intel sockets,
which use the LGA package.
The first one that we're going to
talk about is the LGA 775 socket.
This is also known as socket T. It
was released in 2004, and it has
775 pins as its name states. The
LGA 775 socket
LGA 775 was the successor to
socket 478 and it was designed for the Pentium 4
and Pentium dual core processors.
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LGA 1366 socket
Next is the LGA 1366. This, as
its name states, has 1366 pins
and is also known as socket B.
It was released in 2008 and has
succeeded the LGA 775. The
LGA 1366 uses the Intel Core i7
and Xeon processors.
The LGA 1156 is also known as
socket H or socket H1. This was
released in 2009 and has 1156
pins. This was the first socket to
be used by the Intel core i3 and i5
processors.
LGA 1156 socket
The LGA 1155 is also known as
socket H2. This was designed to
replace the LGA 1156 and has
1155 pins, which is 1 less than
the LGA 1156. But the CPUs
designed for the LGA 1155 and
LGA 1156 are not compatible
LGA 1155 socket
because the notches in the
sockets are different. It was
released in 2011, and these were designed for Intel
CPUs that use the Sandy Bridge and Ivy Bridge
architecture.
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The LGA 1150 is also known as
socket H3. This has 1150 pins
and was released in 2013. The
LGA 1150 supports Haswell and
Broadwell based microprocessors
and has succeeded the LGA
1155.
LGA 2011 socket
LGA 1150 socket
The last of the Intel sockets is the
LGA 2011, which is also known
as socket R. The LGA 2011 has
2011 pins and was released in
2011. It has succeeded the LGA
1366 and was designed for high
performance CPUs that are
based on Sandy Bridge and Ivy
Bridge processors.
The next group of sockets is the
AMD sockets, which utilize the PGA
package. So the first socket is the
AM3. Socket AM3 was released in
2009 and is the successor to the
AM2+. The AM3 has 941 pins.
AM3 socket
Next is socket AM3+, which is the
successor and a modification of the
AM3. It has 942 pins and was
released in 2011. The AM3+ does
retain some compatibility with AM3.
AM3+ socket
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So CPUs designed for AM3 will work in AM3+ sockets.
The next socket is FM1. This
was released in 2011 and has
905 pins. These were designed
for AMD APU processors. APU
stands for accelerated processing
unit. These were designed to act
as a CPU and a graphics
accelerator, on a single chip.
FM1 socket
Next is FM2. This has 904 pins and was released in
2012. There is also FM2+. This was released in
2014. FM2+ has 906 pins and was a new revision to
the FM2.
FM2 socket
FM2+ socket
The central processing unit or CPU
is the main component on the
motherboard. It's the brain of the
computer where all the data
processing takes place. It's in
charge of executing program
instructions and logical calculations.
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The CPU is the largest component on the
motherboard. It's a square chip that is inserted into
the motherboard, in a plastic or metal holder called a
CPU socket. Directly on top of the CPU is the heat
sink and fan, and these are used to keep the CPU
from overheating.
Fan
Heat sink
CPU
CPU socket
The speed of the CPU is measured in megahertz
(MHz). For example, 1 MHz equals 1 million cycles
per second. 500 MHz equals 500 million cycles per
second. 1 gigahertz (GHz) equals 1 billion cycles per
second. Today's high-end processors average a
speed of over 3 GHz per second.
Inside the processor is the
core. The core is where the
reading and execution of
instructions take place. A
processor that has a single
core, processes instructions
one at a time. However, today's
higher-end processors will
Single core processor
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have multiple cores. These are called multi-core
processors, and they can process more instructions
than a single core processor. Which gives a multi-core
the ability to multitask and have a greater overall
performance. Some examples of multi-core processors
are, dual core processors which has two cores. Another
example is a quad core processor, which has four cores.
Dual core processor
Quad core processor
Two of the biggest manufacturers of processors are
Intel and AMD. Intel is the largest manufacturer of
processors and was founded in the late 1960s and has
since dominated the CPU market for a number of years,
until the rise of AMD started to become its chief
competitor. Some of the Intel processors are known as
the 286, 386, 486, Celeron, Pentium, and Xeon
processors.
Intel CPU
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Advanced Micro Devices or AMD, is the second largest
manufacturer of processors, and it was also founded in
the late 1960s. However, AMD didn't really start to
compete with Intel in the CPU market until the mid1990s. Some of the AMD processors are known as the
K5, K6, Athlon, Duran, Sempron, Athlon 64, Opteron,
Phenom, FX, and Ryzen.
AMD CPU
CPUs can come in 32 or 64-bit versions. The difference
between a 32-bit and 64-bit is the way that it handles
memory. The bit size of the CPU refers to the memory it
can address. A 32-bit CPU can reference 2³² bytes of
memory, which equals about 4 GB (gigabytes).
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However, a 64-bit CPU can reference 2 bytes of
memory, which equals to about 16 exabytes, which is 4
billion times more memory than a 32-bit.
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Now that number is so huge that it's a virtually unlimited
because we will never need to use that amount of
memory.
So going back to what we stated before. In order for
data or a program to run, it needs to be loaded into RAM
first. So the data is stored on the hard drive, and then
from the hard drive, it's loaded into RAM. Then once it's
loaded into RAM, the CPU you can now access the data
or run the program. Now in a 32-bit system, since a
maximum amount of memory it can support is 4 GB, it
may not be enough to hold all the data that the CPU
needs to make the computer run as fast as possible. So
when this happens, then some of the data has to be
kept on the hard drive to compensate for the low
memory.
Fr
om
Fr
om
RA
CP M t
U o th
e
Fr
om
th
RA e HD
M
to
RA
CP M t
U o th
e
32 Bit
64 Bit
So instead of data going from RAM to the CPU, it
has to do extra work by going back to the slower
hard drive. When this happens, it slows down the
computer.
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However, on a 64-bit system, it's able to store a lot more
memory than 4 GB. Which means that more data can
be loaded into the faster RAM, than on the slower hard
drive; and because it can store more data on the faster
RAM than on the slower hard drive, the computer is able
to run a lot faster. So in a nutshell, this is why a 64-bit
system is faster than a 32-bit system.
There's also what's called memory cache (CPU cache).
The memory cache uses SRAM or static RAM, which is
very fast memory when compared to regular DRAM that
is used for primary memory. The memory cache is the
CPU's internal memory and its job is to hold data and
instructions waiting to be used by the CPU.
The memory cache rapidly assists in feeding the CPU
data, because RAM is still not fast enough for the CPU.
So basically what cache does, is that it holds common
data that it thinks the CPU is going to access, over and
over again. When the CPU needs to access certain
data, it always checks the faster memory cache first to
see if the data it needs is there, and if it's not, then the
CPU will have to go back to the slower primary memory
or RAM, to find the data it needs. So that's why memory
cache is so important, because if the CPU can access
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what it needs on the faster memory cache, then the
faster the computer will perform.
The memory cache comes in different levels. For
example, there's level 1 cache, which is also called
primary cache. Level 1 cache is located on the CPU
itself. So it runs at the same speed as the processor.
So it's very fast and is the fastest memory cache on the
computer. There was also level 2 cache, which is also
called external cache. Level 2 cache is used to catch
recent data accesses from the processor that were not
caught by the level 1 cache. So in a nutshell, if the CPU
can't find the data it needs on the level 1 cache, it then
searches the level 2 cache for the data. Then if level 2
doesn't have it, then the CPU has to go to the next level,
which is level 3 cache. Level 3 cache is used to catch
recent data accesses from the processor that were not
caught by the level 2 cache. Then if level 3 doesn't
have it, then the CPU has to go back to RAM to find the
data it needs.
Level 3 cache is
located on the
processor.
In modern CPUs,
level 2 cache is
located on the
processor.
Shared between all
the cores in the
CPU.
Level 1, 2, & 3 cache inside the CPU.
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Level 2 cache is generally located on a separate chip on
the motherboard, or in modern CPUs, it would also be
located on the processor. Level 2 cache is larger than
level 1 cache, but it's not as fast as level 1 cache. Level
3 cache is also located on the processor. Level 3 is
larger than level 2, but it's not as fast as level 2 cache.
Level 3 is often referred to as shared cache, because its
memory is shared between all the cores on the CPU,
whereas level 1 and level 2 cache are dedicated to their
own CPU core.
One of the main and one of the most important
components you'll find on the motherboard is the
chipset. Older motherboards were designed with a lot
of different chips, scattered all over the motherboard.
There were chips for
different things, like chips for
bus controllers, memory
controllers, keyboard
controllers, and so on. So
they had a lot of different
chips controlling different
functions on the
motherboard. So as
technology progressed,
Older motherboard with
computer engineers decided
chips scattered all over.
to reduce the number of
chips and have them more
in a centralized location. So instead of having these
different chips scattered all over the motherboard,
controlling different functions; they reduced the number
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Modern motherboard
with a chipset.
of chips to do the same job and
condensed them to only a few
chips, or what's now called a
chipset. And that's what a
chipset is, a chipset is a smaller
set of chips that has replaced a
larger amount of chips. The
chipset's job is to control data
flow between the CPU, the
peripherals, bus lots, and
memory. So all of the different
parts of the motherboard,
communicate with the CPU
through the chipset.
The chipset basically consists of two chips, one is
called the northbridge and the other is called the
southbridge. The northbridge is located in the upper
or northern part of the
motherboard, providing
you're looking at the
motherboard in the upright
position. It's located near
the CPU and is directly
connected to the CPU. It's
also directly connected to
the memory, and the
AGP(outdated) and PCI
express slots. So in order
for the CPU to communicate with the memory, and the
AGP or PCI express bus, it has to go through the north95
bridge first. So the northbridge acts like a
communication middleman between a CPU, AGP, or
PCI express, and memory.
The other chip is called the southbridge. The southbridge is located at the bottom or southern portion of
the motherboard, near the PCI bus slots. The southbridge connects to the PCI bus slots, SATA and IDE
connectors, and USB ports. So the southbridge is
responsible for the lower portion of the motherboard,
while the northbridge is responsible for the upper
portion. There is no direct connection between the
CPU and the lower portion of the motherboard. So if
the PCI slots, USB, IDE, or SATA ports needed to
communicate with the CPU, the information has to go
through the southbridge, then up through the northbridge, and then to the CPU.
Northbridge is
responsible for the
upper portion of the
motherboard.
Southbridge is
responsible for the
lower portion of the
motherboard.
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The northbridge is faster than the southbridge. This is
because the CPU, PCI-E, and memory are the most
used and most important components of the
motherboard. So they need to operate at the highest
speed possible. The slower southbridge communicates
with a PCI bus, SATA and IDE connectors, and USB
ports, and these don't need to be as fast as the other
components. So basically the higher speed
components are connected to the northbridge and the
slower components are connected to the southbridge.
Now both the north and southbridge make these
connections to various parts of the motherboard using
pathways called a bus. A bus as simply a set of
pathways that allows data and signals to travel
between the components
on the motherboard.
The motherboard
contains several kinds of
buses that vary in speed
and bandwidth. So for
example, if a bus speed
is said to operate at 66
MHz, then that means
that particular bus can
send data at 66 million
cycles per second. The
Motherboard buses.
higher the bus speed,
the faster the computer
can send data, which
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improves the performance of the computer. A
motherboard's bus speed generally refers to the speed
of the front side bus. The front side bus is the
connection between the CPU and the northbridge
chipset.
Hyper-threading
Hyper-threading is a technology developed by Intel
that increases the performance of the CPU cores. It
enables multiple threads, which are sequences of
instructions, to be run by each core to make the CPU
run more efficiently. And by doing this, the CPU can
perform more tasks in the same amount of time. So in
a nutshell, you can run a lot of applications at the same
time while maintaining the performance of your
computer when you have a hyper threaded CPU. In
other words your computer is not going to slow down.
Bus Slots
All motherboards are equipped with input/output bus
slots. These are typically located on the bottom rear of
the motherboard. These bus slots are also called
expansion slots because these slots are used to
expand the capability of the computer.
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Motherboard bus
(expansion) slots
For example, if the motherboard doesn't already have a
built-in sound card, then you can add a sound card by
inserting one into one of these bus slots, which gives
your computer the ability to produce sound. Or let's say
the motherboard doesn't have enough USB ports to suit
your needs, well then you can add a USB expansion
card in one of the bus lots to add more USB ports.
A common bus type today is
called PCI, which stands for
peripheral component
interconnect. PCI has
been around since 1993 and
was a standard bus slot for
modern motherboards until
PCI-express came out,
which we'll talk about
shortly. PCI slots are much
faster when compared to the
very old ISA slots, with a
PCI
data path of 32 or 64 bits,
and speeds ranging from
133 to 533 MB/s. They are
also about half the physical length of an ISA slot.
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PCI Express is the latest
version of bus slots. It's
faster than its
predecessor, with speeds
up to 4 GB/s. Unlike
standard PCI, which
transfers data in parallel,
PCI Express transfers data
in serial. Transferring data
in serial is much faster
PCI Express
than parallel because
serial data is transferred in
packets.
PCI Express was designed to succeed all other PCI bus
slots and the older AGP. However, it is not backward
compatible with standard PCI, because the architecture
is very different.
There are four different
slot sizes in PCI Express.
There is PCI Express 1,
4, 8, and 16. PCIe x1 has
one lane for data. A lane
has 4 wires. Two are for
sending, and two are for
receiving. PCIe x4 has
four lanes. PCIe x8 has
8 lanes. And the fastest
slot is PCIe x16, which
has 16 lanes and has
also succeeded the AGP
slot for the video card.
PCIe x16
PCIe x8
PCIe x4
PCIe x1
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There is also the PCI-X
slot, where the X stands for
it extended. The PCI-X slot
is basically an extension of
the old standard PCI slot
and it's almost twice the
length. The PCI-X is a 64bit bus, and it's backwards
compatible with the
standard PCI slot.
PCI-X
It was mainly designed to work with servers and highspeed computers.
There is also the mini PCI
slot and this is what is used
in laptops. It's approximately
one quarter the length of a
standard PCI slot. The mini
PCI slot is a subset of the
standard PCI bus, but it's a
lot smaller. Now you can
insert a regular PCI card into
a mini PCI slot, but you
would have to use a mini
PCI to PCI converter. The
mini PCI is a 32-bit, 33 MHz
bus.
Mini PCI slot
Mini PCI card
101
Mobile Issues
Phones & Laptops
You may come across some
issues when you're dealing with
mobile devices, such cell phones.
And two of the biggest cell phone
operating systems are Apple and
Android. A lot of cell phones
today are touchscreen, and one of
the common problems that you
may encounter with touchscreens
is that sometimes they are not
Touchscreen cell
responsive. You touch the
phone
screen, and nothing happens. So
when this happens, the best thing to do is to power off
the phone and then turn it back on, and a lot of times
this fixes the problem. Or if you still have the issue,
you can try and eject your
SIM card and then reinsert
it. If that doesn’t work, you
may have to do a hard
reset on your cell phone.
Phone SIM card
And you can refer to the
manufacturer's documents for specifics on how to do a
hard reset for your specific device.
Sometimes you may have issues when you touch an
app and the app won't load, or you may have an
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issue with the performance of
your device and you find it to be
running very slow. A lot of this
could be caused by having too
many apps open already, and
those apps are eating up
memory and CPU resources
and slowing the performance of
the device or even freezing it.
So the first thing you should try
is to kill any apps that you have
Phone with a lot
open and see if that fixes the
of apps open.
issue. For example on an
Apple device, the way to kill apps, is to double click
the home button and swipe up each app that’s open,
and it will close that app.
Also with cell phones, you may encounter issues
where your GPS is not working. Certain applications
on your phone require your GPS. So if a certain app
is not working, it could be that your GPS is turned off.
So the first and most obvious
thing to do is to go into the
settings on the phone and
make sure that the GPS is
turned on. Or if your GPS is
turned on, and you're still
having issues, you have to
remember, that your GPS uses
satellites for communication.
So for example, if there's a
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cloudy day, then that could interfere with satellite
communication.
As far as troubleshooting
issues with laptops; one of
the main problems is that
sometimes when you turn on
the power, but your screen is
blank. Nothing shows up on
the screen. You may hear
the fans running, you may
No display (blank
see the LEDs turn on, but
screen) on a laptop.
your screen is still blank.
This is called a no display
issue. Now, this could happen for a few reasons. But
the best thing to do right from the start is if you have an
external monitor, go ahead and connect an external
monitor to your laptop and see if an image shows up on
an external monitor. Now if an image does show up on
your external monitor, then that means your LCD
monitor on your laptop is bad, and it needs to be
replaced.
Laptop connected to external monitor
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Another problem is that
when you turn on the
laptop, you see an image
that's very faint. The
display is very dim.
In this case, most likely
you would have to replace
the inverter. The inverter
is a small circuit board
Dim display
that supplies power to the
LCD monitor. It converts
DC current to AC current.
The inverter is usually
Inverter
mounted inside the
display panel, just below
the screen.
If you press the power button on your laptop and let's
say that nothing happens. In other words, you don't
see any power LEDs, your screen is blank, and you
don't hear any fans turning. One of the first things to
check is making sure your battery charger is plugged
into the wall and to your laptop. Once you verify that,
and still nothing happens? Well then most likely your
laptop’s motherboard is dead and needs to be
replaced.
Laptop plugged into
a wall outlet
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A flickering monitor can also be related to a bad LCD
or inverter, especially if the failure is related to
movement; in other words, if the flickering happens
when you physically move the laptop. So most likely it
is a hardware failure.
Problems with keys sticking is
another issue that can happen
with laptops. One thing you'll
notice is that laptop keyboards
are not as durable as regular
desktop keyboards. So they are
more susceptible to wear and
tear, and tend to wear out a lot faster. So if you're
going to repair a laptop keyboard or replace the
keyboard, you need to be extra careful.
Another issue on laptops, is sometimes people
complain that as their typing on the keyboard, the
mouse cursor moves all by itself. This is known as
ghost cursor.
Palms of hands or
sleeves on a shirt,
touching the
touchpad, could
cause a ghost cursor.
The main reason (especially in my personal
experience in dealing with my customers) is that when
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a person types on the laptop keyboard, a lot of times
they don't realize that the palms of their hands or the
sleeves on their shirt are touching the touchpad.
Which will move the cursor. So the best way to solve
this problem is to go into the software touchpad
settings on the laptop and disable the tap
feature. Another issue that could cause a ghost
cursor could be improper touchpad drivers. So the
best thing to do is to go to the manufacturer's website
and download the correct and latest drivers for the
touchpad.
A very common issue that
happens with laptops is
overheating. A lot of
people complain that as
they are working on their
laptop, the laptop shuts
down or freezes. Which is a
very common symptom of
overheating. Laptops have
air vents either on the side
or on the bottom of a laptop,
along with fans. And air
passes through these vents and fans to help cool the
laptop. But if these vents are blocked, for example
with dust, it will hinder the laptop’s cooling ability. So
the best way to fix this problem is to get a can of
compressed air and blow out the vents and fans and
free them from any dust or debris.
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Use a can of compressed air to free the laptop's
fans and vents from dust and debris.
But another issue that causes a laptop to overheat is
a lot of times people use their laptops, and they're not
placing them on a flat hard surface. For example,
they're using them on soft surfaces like their couch or
on their bed. When this happens, a lot of times the
vents and fans will get blocked and will hinder air
circulation, especially if the fans and vents are on the
bottom of the laptop.
Hard surface
GOOD
Soft surface
BAD
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You may also encounter an issue with your laptop
where the battery is not being charged. Your battery
is in the laptop and a battery charger is plugged in,
but you'll notice that there was an indicator informing
you that the battery is not charging.
Now most likely this could be a problem with the
battery itself, and it needs to be replaced. Or it could
also be a problem with the laptop's motherboard. Or
in another scenario, let's say your battery is fully
charged, but the battery only lasts a few minutes
before it discharges. Now, this is a very common
issue with older laptops. Often times when laptops
reach around 5 years old, the battery will only last a
few minutes on a full charge, for example, they may
only last about 10 minutes. And this happens
because batteries lose their capacity to hold a charge
as they get older. So all you have to do is replace the
battery for the laptop.
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All laptops have the capability of wireless networking.
And a lot of times you may have a situation where you
have an intermittent wireless connection. This could
be due to a problem where there is interference
between your laptop and your wireless router, or it
could be that you might be out of range of your
wireless router.
Out of range or interference issues could cause
intermittent wireless problems.
Another intermittent wireless issue could be that you
would need to update your wireless network card
drivers. Especially when there's a new operating
system that's been released. In fact, I have personally
found this issue to be common with the release of
Microsoft Windows 10, where a common fix for
an internment wireless issue, is to go to the laptop
manufacturer's website and update your wireless
network card drivers.
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BIOS / CMOS
BIOS stands for basic input
output system. The BIOS
is software that is built into
the motherboard that
initializes the computer’s
peripherals as the computer
is being booted. Some of
these peripherals include the
keyboard, mouse, video
card, optical drives, and so
on. After it initializes the
BIOS initializing the
peripherals, it then searches
computer at startup.
for a boot device, like an
optical drive, USB drive, or a hard drive, to boot software
or an operating system.
The BIOS software is stored on the BIOS chip on the
motherboard. The BIOS chip is non-volatile, which
means that the software and settings are retained even
after the power is turned off.
BIOS chip stores the BIOS
software (firmware).
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Some popular vendors of BIOS software are American
Megatrends and Phoenix Technologies.
After a computer is turned off, and if the power cable is
unplugged, the computer needs to maintain certain
settings. Such as the date, time, and hardware
settings. And these setting are stored on the
motherboard in a special chip called a CMOS chip.
CMOS stands for complementary metallic oxide
semiconductor. And in order for the CMOS chip to
maintain these settings, it needs a battery. This battery
is called the CMOS battery.
CMOS battery
The CMOS battery is a small button cell battery, which
can be seen on the surface of the motherboard. It's
usually located on the bottom right-hand corner. The
CMOS battery is basically the same type that is typically
used in wrist watches.
When you turn on a computer, the computer does
what’s called a power on self test or POST, which is
run by the BIOS. It tests the computer to make sure all
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the requirements are met and the hardware is working
correctly before continuing.
BIOS doing a POST (power on self test).
So after POST has passed, and as stated before, the
BIOS searches for something to boot from such as an
operating system, which is typically loaded on the hard
drive. But the computer doesn’t necessarily have to
boot to an operating system.
Hard drive
Optical drive
USB
FLOPPY
Boot priority screen in CMOS setup.
It can also boot from other things such as an optical
drive or a USB drive, just as long as those drives
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have the necessary boot files on them. And how the
BIOS determines which device to boot from, depends
on the boot priority in the CMOS settings. The boot
priority screen is where you can make changes in the
boot order.
So for example, If the optical drive is set as the first
boot device, then the BIOS will check that first and look
for booting software and if it doesn’t find anything, it will
move on to the 2nd device on the list and check that
next. Then it will continue down the list until it finds
something to boot from. But, you can change the boot
priority in the CMOS setup and put in any order you
choose. Then once you make the change, you just
save the settings and the next time you reboot the
computer, the settings will take effect.
The BIOS will go down the list of boot
devices, based on the order, to find a drive
that has boot software on it.
Now there are certain things you can do while you're in
the BIOS. For example, you can set the date and
time.
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The data and time should be accurate because the
operating system does reference it.
Setting the date and time in the BIOS.
Other things you can do in the BIOS, is enable or
disable certain devices. For example, if your
motherboard has a built-in video, network, or sound
card, you can disable these devices to save resources
if you're not using them. But that's only if you already
have separate adapter cards installed on the
motherboard that already gives you these capabilities.
The BIOS also allows you to modify the CPU clock
speed by either increasing the clock speed to make the
computer run faster, (which will increase the
temperature) or by reducing the clock speed which will
make the computer run slower (which will lower the
temperature). Reducing the clock speed can be
especially useful if your computer is having overheating
issues. And speaking of temperature, the BIOS can
also monitor the temperature of the CPU.
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The BIOS has a built-in safety
mechanism, that if the CPU
reaches a certain temperature
threshold, it will automatically
shut down the computer. Or if
it detects that the CPU fan is
not spinning, it will shut down
the computer to prevent
damage to the CPU from
overheating.
You can change the clock speeds in the BIOS.
But these temperature thresholds can be modified in
the BIOS if you want to, by either increasing or
decreasing the temperature threshold. And you can
also modify the fan speeds of the computer.
You can also enable or disable virtualization in the
BIOS. Virtualization is a technology that enables your
computer to run multiple operating systems in different
partitions. The operating systems are not actual, but
they are virtual. So if your computer is preventing you
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from installing or running virtualization software, it
could be that virtualization is disabled in the BIOS.
One way to protect your computer from unauthorized
users is by using password protection in the BIOS.
Using a BIOS password not only prevents changes to
the settings, but it also protects the system from
booting. A user cannot boot up the computer or make
any changes in BIOS without the password.
Password protection in the BIOS.
Another BIOS security measure is drive lock. Drive
lock prevents the hard drive from being accessed by
using password protection. When drive lock is
enabled in the BIOS, a user cannot access the drive
without the password. The password is stored on the
hard drive, but it cannot be read or removed.
Some BIOS systems have an intrusion detection
feature. This feature detects if the computer case has
been opened and alerts the user.
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ALERT! COVER HAS BEEN OPENED.
Intrusion detection system alerts you if the
computer case has been opened.
And some computers,
especially laptops, can be
equipped with LoJack, which
is a service that can locate
your computer if it has been
stolen.
THIEF!
When you turn on a computer, the computer does
what’s called a power on self test, or POST. It tests
the computer to make sure
all the requirements are met
and if the hardware is
working correctly before
starting the operating
system. If the computer
passes the test, the internal
speaker will make a short
A single beep indicates a
single beep, which indicates
successful POST
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the computer has passed the test and is booting up
normally. However, if there are no beeps or multiple
beeps, then that means
that the computer failed
the test and something is
wrong, and the computer
needs further trouble
shooting to find out what
the problem is.
Whether there are no
beeps or multiple beeps,
Multiple beeps indicates a
the computer will generate
problem.
a beep code to help you
pinpoint the problem. For example, if the computer
generates 3 long beeps, then that could indicate a
keyboard error. Or if the computer generates a
continuous short beep, then that could indicate a
problem with a RAM module. Whatever BIOS is
installed on your computer’s motherboard, you can
refer to the manufacturer’s documentation to find a list
of beep codes and what they mean.
A new type of BIOS is called UEFI. UEFI stands for
unified extensible firmware interface. Now most, if
not all new motherboards, are shipped with his newer
type of BIOS. UEFI has several advantages over the
old BIOS. And the first and most obvious, just by
looking at it, is that it has a user-friendly graphical user
interface that supports different colors and even
animations. Whereas the old BIOS has your typical
blue screen that resembles the Windows blue screen of
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BIOS (OLD)
UEFI (NEW)
death. UEFI can also recognize larger hard drives, and
you can even use a mouse in the UEFI interface, as
compared to the old BIOS, where mouse support was
not even available and you had to use your keyboard
only. UEFI also has a built-in feature called secure
boot. Secure boot stops any digitally unsigned drivers
from loading and it helps to stop malicious software
such as rootkits.
Larger view of a UEFI
interface
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Front Panel Connector
Typically located at the bottom right-hand corner of the
motherboard, you'll find what's called the front panel
connector. And this is where you would plug and wires
that connect to items that are in the front bezel of the
computer case. So for example, there is a power button
connector, and this turns a computer on or off. There's
also the power LED, which indicates when the computer
is on or off, or in standby mode. There is also the hard
drive LED, which indicates when there is hard drive
activity. There is also the reset switch, which restarts
the computer by doing a hard boot. And there is also a
speaker connector, which is used to plug in the internal
speaker of the computer. Often times the front panel
connector will be color-coded to help identify where the
wires connect to, which makes knowing where to
connect the wires a lot easier.
Color-coded, front panel
connector on a
motherboard.
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Most computers today will have certain common
connections on the front panel of the computer case, for
easy access. For example, you may find some USB
ports. You may also find some audio ports, one for
headphones or speakers, and another one for a
microphone. You will also find on the front panel, the
power button, which is used for turning on or off the
computer. You will also see a reset button, which is
used for doing a hard reboot. And there is also the hard
drive activity light. And when this light blinks, it means
that there is activity in the computer. In other words, the
hard drive is being accessed.
Easy access connections, and LEDs on
the front panel of the computer case.
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RAID
Storage is another very important part of fault
tolerance. If something were to happen to a company's
data, such as a disk failure that results in data loss,
then that is going to have a serious impact on how a
company performs. That's why we need to make sure
that if a disk does fail, that
no data loss will occur. So
one of the best ways to
prevent data loss is RAID.
RAID stands for redundant
array of independent
disks. In a RAID set up, the
data is copied on multiple
disks. So that in the event of
a disk failure, no data will be lost. Now there are 4
common levels of RAID. There is RAID 0, RAID 1,
RAID 5, and RAID 10.
Now RAID 0 is not fault tolerant. In fact, RAID 0
shouldn't even be called RAID, because not only does
it not provide fault tolerance, but it actually increases a
chance for data loss. Because in a RAID 0, the data is
not duplicated, but it's actually spread or striped across
two separate disks. So if just one of these disks fails,
then all the data will be lost. So the only reason why
you would want to use Raid 0, is speed. Because
when you have two disks controllers working instead of
one, then accessing data is much faster.
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Spread or
striped,
over two
disks.
DISK 1
DISK 2
RAID 0 is not fault tolerant.
It's only for speed.
Now RAID 1 is fault tolerant. In a RAID 1 setup, the
data is copied to more than one disk. So disk 2 would
have the exact same copy of the data, as disk 1. So in
the event of a single disk failure, no data loss would
happen, because the other disk has a duplicate copy.
There are also two different setups in RAID 1,
mirroring and duplexing. Mirroring is when all the
disks use the same controller. But duplexing is when
each disk has their own controller. So duplexing is
more fault tolerant of the two setups, because it would
still continue to function if a controller goes down.
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Each disk
has the
same
data.
DISK 1
DISK 2
RAID 1 - the data is copied on
more than 1 disk.
Now RAID 1 is fault tolerant. In a RAID 1 setup, the
data is copied to more than one disk. So disk 2 would
have the exact same copy of the data, as disk 1. So in
the event of a single disk failure, no data loss
would happen, because the other disk has a duplicate
copy. There are also two different setups in RAID 1,
mirroring and duplexing. Mirroring is when all the
disks use the same controller. But duplexing is when
each disk has their own controller. So duplexing is
more fault tolerant of the two setups, because it would
still continue to function if a controller goes down.
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Next, we'll talk about RAID 5. In order to use RAID 5,
you need to have 3 or more disks. RAID 5 is probably
the most common setup that is used, because it's fast
and it can store a large amount of data. In a RAID 5
setup, the data is not duplicated, but it's striped or
spread across multiple disks. And in addition to the
data, there was another very important piece of
information that is being evenly spread across all the
disks. This information is called parity. And parity is
used to rebuild the data in the event of a disk failure.
But there is a downside to RAID 5, because since the
equivalent of an entire disk is used to store parity, it
reduces the collective amount of data that can be
stored in this array. So for example, if all four of these
disks (see graphic below) were 1 TB each, then that
totals 4 TB. But in a RAID 5 setup, the total amount
that would be used for data storage would be 3 TB,
because the equivalent of 1 entire disk (1 TB) would be
used to store parity.
DISK 1
DISK 2
DISK 3
DISK 4
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RAID 5 - the data is spread or striped across
multiple disks. In addition to parity.
Finally, there is RAID 10. RAID 10 is basically what
the name says. It's combining RAID 1 and RAID 0
together, and you need to use a minimum of four disks.
So in a RAID 10 setup, a set of 2 disks are mirrored
using a RAID 1 setup. Then both sets of the two disks
are striped using RAID 0. So RAID 10 benefits from
the fault tolerance of RAID 1, and the speed of RAID 0.
But the downside in a RAID 10, is that you can only
use 50% of the capacity for data storage. So if you are
using 4 disks in a RAID 10 setup, you can only use two
of them for actual storage.
DISK 1
DISK 2
DISK 3
DISK 4
RAID 10 - combines RAID 1 & RAID 0. In RAID 10, a set of
2 disks are mirrored using RAID 1. Then both sets of the
2 disks are striped using RAID 0.
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Networking Cables
& Connectors
This is the RJ-11 connector. RJ
stands for registered jack. This is
a 4 wire connector, used mainly to
connect telephone equipment. But
as far as networking, the RJ-11 is
used to connect computers to local
RJ-11
area networks through the
computer's modem. The RJ-11
locks itself and to place by a single locking tab, and it
resembles an RJ-45, but it's a little bit smaller.
RJ-45
Now the RJ-45 is by far the
most common network
connector. This is an 8 wire
connector, used to connect
computers to local area
networks. And like the RJ11, it also locks itself into
place by a single locking
tab, and it also resembles
or RJ-11, but it's a little bit
larger.
The BNC connector is a common type of RF connector
that is used on coaxial cable. BNC stands for bayonet
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neill concelman. And the
BNC is used for both analog
and digital video
transmissions, as well as
audio.
BNC
F-type
This connector is called the Ftype. Now, this is a threaded
connector, typically used on
coaxial cables. These are
primarily used by cable
providers to attach to cable
modems. The F-type hand
tightens by an attached nut.
This is the IEEE 1394
connector, and this is also
known as firewire. Firewire
is recognized by its D shape.
This type of connection is
becoming less popular on
desktops and laptops. It's
Firewire
commonly associated with
attaching peripheral devices
such as digital cameras and printers, rather than being
used as network connections.
This is the USB connector. The USB is very common
on desktops and laptops. Just about every kind of
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peripheral connects to a computer, using the USB
connector. There are also several different types of
USB connectors. There is the type A, type B, the mini
USB, and the micro USB.
TYPE A
TYPE B
MINI
MICRO
A newer type of interface for attaching external
peripherals is called Thunderbolt. Thunderbolt is a
high-speed technology
interface that outputs one
serial signal from a
combination of PCI express
and the DisplayPort.
Thunderbolt was released in
Thunderbolt
2011, and was mainly used in
Apple products. And now it has become available to
PCs. There are three different versions of
Thunderbolt. Versions 1 and 2, use the same
connector as the mini DisplayPort. And version 3,
uses a USB type C connector.
Version 1 & 2
Version 3
Another type of connector is called RCA. The RCA is
an older type connector that was produced in the
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1940s. These were
primarily used to carry
video and audio signals. A
lot of times you may see
RCA connectors in a group
of 3, a yellow, a white, and
a red. The white and red
are used for audio, such as
a left and right speaker.
And the yellow would be
used for video.
LC
This fiber optic connector
is called the ST or straight
tip. This uses a half-twist
bayonet type of lock and is
commonly used with single
mode fiber optic cable.
RCA connectors
Our next connector is
called the LC or local
connector. And this is a
fiber optic connector. It
uses a jack similar to the
RJ-45. This type of
connector is commonly
used between floors in a
building.
ST
Our last fiber optic connector is called the SC or
standard connector. And this uses a push-pull
connector similar to audio and video plugs. And like
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the LC connector, this is also commonly used
between floors in a building.
SC
The term plenum refers to a space in a building where
there is open airflow circulation. And this is usually
between the drop ceiling and the structural ceiling.
Buildings that don't have plenum spaces have air ducts
encapsulating the airflow. So as a result, buildings that
have plenum spaces, where there is adequate open
airflow, are more prone to fires than buildings that don't
have plenum spaces.
Plenum
Open air flow (dangerous)
Non Plenum
Encapsulated air flow (safer)
And because of this, cables that run through plenum
spaces must meet certain requirements. First, they
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must be more fire-resistant. And secondly, they must
not produce any toxic fumes if they are burned.
Sometimes there might be cases in your home or office,
where you wanted a certain computer in a certain part of
the building, to be able to access the internet or to be
networked. And for whatever reason, network cabling
or Wi-Fi just wasn't an option in that part of the building.
Maybe because of difficulties in the structure of the
building, interference, or whatever. So a new
technology gave the ability to network using the existing
electrical system of the building. Ethernet over
powerline gives the ability of Ethernet networking over
power.
Powerline
network adapter
So, for example, let's say you needed a computer to be
able to access the internet. But for some reason, you
can't get any network cables or any Wi-Fi signal to
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reach that computer. So, in this case, we're going to
use Ethernet over power. So we're going to need a
couple of powerline adapters. These powerline
adapters plug directly into a power outlet and they have
a built-in Ethernet port for an RJ-45 connector.
Computer plugged into a powerline
network adapter.
So one adapter plugs into a power outlet next to the
computer that you want to have internet access
(above). Then you would connect a network cable from
the adapter to the computer. Then the other adapter
plugs into the power outlet next to the modem or router
(below) and then connected with a network cable.
Modem plugged into a
powerline network adapter.
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So now Ethernet data will use the building's electrical
wiring to deliver networking data to the other
powerline adapter so that the computer can access
the internet.
Another standard is called
Ethernet over HDMI. The
HDMI 1.4 specification adds
another channel to an HDMI
cable for data, which will
have the capability of
network communication. So
HDMI cable
the connected devices that
use this feature will have the
ability to send and receive data at 100 Mb/s Ethernet.
So, in addition to video and audio on a single cable, the
HDMI cable will have another ability of Ethernet
networking.
Wiring Standards
The terms 568A and 568B, refer to a set of wiring
standards developed by TIA / EIA, which is also known
as the Telecommunications
Industry Association. And
these terms define the
rules on how twisted pair
cables should be wired to
RJ-45 connectors.
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The 568A standard is wired in this order: White/green,
then green, white/orange, blue, white/blue, orange,
white/brown, and brown.
White - Green
Green
White - Orange
Blue
White - Blue
Orange
White - Brown
Brown
568A wiring standard
And the 568B standard is wired in the following order:
white/orange, then orange, white/green, blue,
white/blue, green, white/brown, and brown.
White - Orange
Orange
White - Green
Blue
White - Blue
Green
White - Brown
Brown
568B wiring standard
There is no difference in the functionality as to which
standard is used.
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Whether you choose to use the A or B wiring standard,
if both ends of the cable are wired using the same
standard, then this is known as a straight cable. For
example, this cable is wired on both ends using the
568A standard.
Straight cable
A straight cable allows signals to pass straight through
from end to end. This is the most common type of
cable and it's used to connect computers to hubs,
switches, or modems.
Another type of cable is called a crossover. A
crossover cable is created when both ends of the cable
are wired using the two different standards. For
example, one end is wired using the A standard, and
the other end is wired it using the B standard.
Crossover cable
Crossover cables are used to connect two similar
devices together. For example, you can use a
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crossover cable to connect two computers directly to
each other without using a hub or switch. They are also
used to connect hubs or switches to each other.
A rollover cable is created when both ends are wired
completely opposite of each other. These are used to
connect a computer or a terminal, to a router’s console
port.
Both ends are wired
completely opposite
from each other.
Rollover cable
A loopback cable is used for testing purposes. It’s to
make a computer think that it's connected to a network.
To make a loopback cable, you connect pin 1 to pin 3
and pin 2 to pin 6.
Loopback cable
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Firewalls
A firewall can be either software or hardware. It's a
system that is designed to prevent unauthorized access
from entering a private network, by filtering the
information that comes in from the internet. It blocks
unwanted traffic and permits wanted traffic. So
basically it filters the incoming network data packets
and determines by its access rules if it is allowed to
enter the network. In today's high tech world, a firewall
is essential to every business to keep their network
safe.
Firewall in a private network.
Firewalls come in different types. One type is called a
host-based firewall. A host-based firewall is a
software firewall. This is the kind of firewall that is
installed on a computer and it protects that computer
only and nothing else. For example, later versions of
Microsoft operating systems come pre-packaged with a
host-based firewall. You can turn a host-based firewall
on or off, and you can also create exceptions to the
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firewall based on the application name on the
exceptions tab (see below). And of course, you can
always purchase a third-party firewall and install it on
your computer.
Host-based Firewall on
Microsoft Windows.
Exceptions tab on a hostbased firewall.
Media Types
Today there are several different categories of twisted
pair cables that you're going to need to know for the
exam. The difference between these is the maximum
speed that can handle without having any crosstalk
(interference). The numbers of these categories
represent the tightness of the twists that are applied to
the wires. And you can see an illustration below of the
categories and speeds of different twisted pair cables.
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CATEGORY
SPEED
10 Mbps
100 Mbps
1,000 Mbps
e = enhanced
1,000 Mbps
10,000 Mbps (cable
length under 100 meters)
10,000 Mbps
10,000 Mbps
a = augmented
Added shielding to the
wires.
Unshielded twisted pair (UTP) is by far the most
common type of table that is used today. It consists of
4 pairs of unshielded wires twisted around each other.
The wires are twisted to prevent electromagnetic
interference or crosstalk. This type of cabling is mainly
used on local area networks.
Unshielded twisted pair (UTP) cable
Now shielded twisted pair (STP) is very similar to
unshielded twisted pair, except that it has a foil shield
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that covers the wires. This shielding adds a layer of
protection against electromagnetic interference,
leaking into and out of a cable.
Shielded twisted pair (STP) cable adds a
foil shield that covers the wires.
This is a coaxial cable. This
is used today primarily by
cable providers to provide a
computer with broadband
internet connection. Early on
it was used as a backbone
for networks, such as a bus
Coaxial cable
network. There are also
two common types of
coaxial cable. The first type is RG-6. RG-6 is made for
long distances and is commonly used for cable
television and internet connection. The second type is
RG-59, and this is made for short distances and is
commonly used for high definition and high quality
video.
Now we're getting into fiber optic cables. Below, are
cutaway views of fiber optic cables and a light source.
Fiber optic cable uses pulses of light to send data, and
as a result, it is very fast and it can span for great
distances.
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Now there were two different modes in fiber optics:
Single-mode fiber and multi-mode fiber. Single-mode
fiber is a fiber optic cable that allows light to enter only at
a single angle. So when this type of transmission of light
enters at this angle, it can span for long distances.
Single-mode fiber - Light enters at a single
angle. Made for long distances.
Below is multi-mode fiber. The difference between
multi-mode and single-mode, is that in multi-mode, light
travels in multiple beams that reflect off the walls of the
cable. And unlike single-mode fiber, multi-mode fiber is
made for short distances.
Multi-mode fiber - Light reflects off the walls of
the cable. Made for short distances.
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Network
Components
Cable modem
Those of you who have
broadband cable internet will
recognize this device. And yes,
this is your typical DOCSIS
cable modem. DOCSIS stands
for data over cable service
interface specifications. The
DOCSIS 3.1 specification
supports speeds of 10 gigabit
downstream and 1 gigabit
upstream. The DOCSIS modem
handles both incoming and
outgoing data signals, including
internet, video, and voice.
A hub is a device that has
multiple ports that accepts
Ethernet connections from
network devices. A hub is
considered not to be
intelligent because it does
Hub
not filter any data or has any
intelligence as to where
data is supposed to be sent. When a data packet
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arrives at one of the ports, it is copied to all other ports,
so all the devices on that hub sees that data packet.
So this not only creates security concerns, but it also
creates unnecessary traffic on the network.
Now a switch is very similar to a hub. It's also a device
that has multiple ports that accepts Ethernet
connections from network devices. But unlike a hub, a
switch is intelligent. A switch can actually learn the
physical addresses of the
devices that are connected
to it, and it stores these
addresses in a table. So
when a data packet is sent
to a switch, it’s directed
only to the intended
Switch
destination port. That's the
major difference between
a hub and a switch. So
as a result, switches are far more preferred over hubs,
because they reduce any unnecessary traffic on the
network.
A bridge is used to divide a network into separate
collision domains. For example, if you have a network
that is segmented into two by a couple of hubs, then all
the broadcast traffic from the two segments are seen by
all the computers. And this causes unnecessary traffic.
So that is where a bridge can be helpful. If you add a
bridge to this network, it will reduce any unnecessary
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traffic between the two segments by filtering the data
based on their MAC address. The bridge only allows
data to crossover if it meets the required MAC address
of the destination, because a bridge keeps a record of
all the MAC addresses of the NICs that are connected
to it. And it will also block all data from crossing over if
it fails to meet this requirement.
Bridge
Segment 1
Segment 2
Bridges reduce unnecessary traffic on a network by
allowing or blocking data based on their MAC address.
A segment is part of a network that is separated
from the rest of the network by a device, such as a
hub, switch, bridge, or router.
Now a router does exactly what its name implies. A
router is a device that routes or forwards data from one
network to another based on their IP address. When a
data packet is received from the router, the router
inspects the packet and determines if the packet was
meant for its own network or if it's meant for another
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network. If the router determines that the data packet
is meant for its own network, it receives it. But if it's
not meant for its own network, it sends it off to another
network. So a router is essentially the gateway for
network.
Router
Networking devices need electrical power to function,
and that's why they have a separate power cable. But
some networking devices don't have a power cable.
It’s not that they don't need electrical power, it's just
that they get their power and data from the same
cable, which is through the Ethernet cable. And this
technology is known as PoE, which stands for power
over Ethernet.
Here is a switch and a hub that receive power from
the network Ethernet cable, instead of a separate
power cable.
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A wireless access point is basically a wireless hub
that is used by wireless devices. It connects to a wired
network and relays data between the wired network
and the wireless device for communication purposes.
In the illustration below, you see a wireless access
point that's wired to a network so that the wireless
laptop can communicate with the network.
Wireless access
point (WAP)
A network interface card or NIC, is used to connect a
computer to a network. It is basically a circuit board
with a network adapter that is installed on your
computer. Its job is to convert
incoming serial data into parallel
data, so that the computer can
understand it. A NIC provides a
constant dedicated connection to a
network. And every NIC has its
own unique identifier, called a
NIC
MAC address.
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A modem card is a device that allows a computer to
transmit data over normal telephone lines. The data
coming in from the telephone lines is analog, however,
the data in a computer is all digital. So when the
analog data comes in from the telephone lines, the
modem's job is to convert into a digital form so the
computer can understand it. So that's basically what a
modem does, it converts analog data into digital data.
And the maximum speed of most modems today is 56
kbit/s.
Modem card
A patch panel is a panel that has multiple cable
connections that connect incoming and outgoing patch
cables in a local area network. It allows network
administrators the convenience of arranging or
rearranging circuits if necessary. For example, here we
have a patch panel that has several UTP patch cables
attached.
Patch panel
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Wireless Technologies
The IEEE is an international organization for the
advancement of technology related to electricity. And
they are responsible for a set of standards for a project
called the 802 project. One of these standards is the
802.11 standard, which is wireless. Wireless
technology is becoming more and more popular, and
today there are five wireless standards. There are the
A, B, G, N, and AC standards. And below is a chart of
the speed, frequencies, and release year for each one.
So starting with the first wireless standard, which is 802.
11a, which came out in 1999, and the latest standard is
the 802.11ac standard, which was released in 2014.
Bluetooth is a short-range radio that provides a way to
connect and exchange information between devices
such as laptops, cell phones, and tablets. It operates at
2.4 Ghz and is capable of transmitting both voice
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and data. The latest standard of the bluetooth has a
transfer speed of 24 Mbit/s and has a maximum range
of approximately 100 meters.
Bluetooth is used in devices
such as laptops, tablets, and
cell phones.
IP Address
An IP address is a numeric address. It's an identifier
for a computer or device on a network. Every device
has to have an IP address for communication purposes.
The IP address consists of two parts, the first part is the
network address, and the second part is the host
address. There are also two versions of IP addresses.
The first one is the most common one, it's called IP
version 4 (IPv4). And the second type is IP version 6
(IPv6).
66 . 94 . 234 . 13
IPv4 address
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IPv4 is the current version (but not for long) of IP
addresses. It's a 32-bit numeric address, written as
four numbers, separated by periods. Each group of
numbers that are separated by periods is called an
octet.
Octet
66 . 94 . 234 . 13
IPv4 address
The number range in each octet is 0 - 255. This
address version can produce over 4 billion unique
addresses.
When the internet was first developed, programmers
didn't realize how big it would become. They thought
that IPv4, which produced over four billion addresses,
would be enough, but they were wrong. IPv6 is the
next generation of IP addresses. The main difference
between IPv4 and IPv6 is the length of the address.
The IPv4 address is a 32-bit numeric address, whereas
IPv6 is a 128-bit hexadecimal address.
76DC:4F59:34CF:71CD:9DC6:89CD:45D6:67A2
IPv6 address
Hexadecimal uses both numbers and alphabets in the
address. So with this type of address, IPv6 can produce
an unbelievable 340 undecillion IP addresses!
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That's the number 340 with 36 digits after it. So as you
might have guessed, IPv6 is more than enough for the
foreseeable future.
As stated previously, an IP address has two parts, one
part is designated for the network, and the remaining is
designated for the host. So the way to tell which portion
belongs to either the network or the host is where the
subnet mask comes in. A subnet mask is a number
that resembles an IP address. It reveals how many bits
in the IP address are used for the network, by masking
the network portion of the IP address.
IP address
173 . 16 . 0 . 0
Subnet mask
255 . 255 . 0 . 0
So in this subnet mask, the first two octets are 255. So
if we were to look at this subnet mask in binary form,
the first two octets would be all 1s, because when you
count all the numbers in an octet, it will equal 255.
Subnet mask
255 . 255 . 0 . 0
11111111 . 11111111 . 00000000 . 00000000
Subnet mask in binary form.
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IP address in binary form.
10101101 . 0 0 0 1 0 0 0 . 0 0 0 0 0 0 0 0 . 0 0 0 0 0 0 0 0
11111111 . 11111111 . 0 0 0 0 0 0 0 0 . 0 0 0 0 0 0 0 0
Subnet mask in binary form.
So above, we have our IP address and subnet mask in
binary form. So the way to tell which portion of this
IP address is the network portion is when the subnet
mask binary digit is a 1, it will indicate the position of the
IP address that defines the network. So we'll cross out
(below) all the digits in the IP address that line up with
the 1s in the subnet mask. And when you do this, it will
reveal that the first two octets are the network portion,
and the remaining is the host portion.
10101101 . 0 0 0 1 0 0 0 . 0 0 0 0 0 0 0 0 . 0 0 0 0 0 0 0 0
11111111 . 11111111 . 0 0 0 0 0 0 0 0 . 0 0 0 0 0 0 0 0
1 7 3
.
1 6
Network portion
.
0
.
0
Host portion
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Below is a chart of the default subnet masks for class
A, B, and C, IP addresses. Noticed the change of the
locations of the network and host portions between
them. You should memorize these default subnet
mask classes.
Class
Subnet Mask
A
255.0.0.0
B
255.255.0.0
C
255.255.255.0
. hhhhhhhh . hhhhhhhh . hhhhhhhh
NNNNNNNN . NNNNNNNN . hhhhhhhh . hhhhhhhh
NNNNNNNN . NNNNNNNN . NNNNNNNN . hhhhhhhh
NNNNNNNN
N = NETWORK
h = HOST
Chart for the default subnet mask for the different classes.
IP addresses are assigned to different organizations in
blocks. And these blocks are divided into five classes.
But for the exam, you only need to know 3 of them (see
below). They are class A, class B, and class C. You
can tell by the number in the first octet which class an
IP address belongs to.
Default Subnet Mask
Class
First Octet Address
A
1-126
255.0.0.0
B
128-191
255.255.0.0
C
192-223
255.255.255.0
NOTE: 127 is reserved for loopback testing.
Public IP addresses are publicly registered on the
internet. Which basically means that if you have a public
IP address, you have access to the internet. But private
IP addresses are different. A private IP is not publicly
registered, so you can't directly access the internet
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with a private IP. So, for example, let's say you have a
small business and you need 10 public IP addresses so
your employees can access the internet. Now you could
contact your ISP and ask them for these additional IP
addresses, but that would be very expensive and
unnecessary.
10 public IP addresses being used.
So that's where private IP addressing comes in. In
private IP addressing, you can create these ten private
IP addresses and just have one publicly registered IP
address from your ISP (see below). These ten private
IPs would then be translated into the one public IP, so
your employees can have access to the internet. This
not only saves money, but it also helps prevent having a
shortage of public IP addresses.
1 public IP address being used.
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IP Addressing
Methods
Every computer on the network has an IP address for
communication purposes. There are two ways that a
computer can be assigned an IP address. It could be
done either by using a dynamic IP, or a static IP. A
dynamic IP is where a computer gets an IP address
automatically from a DHCP server. DHCP stands for
dynamic host configuration protocol. A DHCP server
automatically assigns a computer with an IP address,
and in addition to an IP address, it can also assign a
subnet mask, default gateway, and a DNS server.
10.0.0.1
DHCP server
Computer
DHCP server assigning an IP address to a
computer.
Below, we have the TCP/IP properties window open for
the network interface card on a Windows machine. And
as you can see, this computer is set to obtain an IP
address automatically. So when you choose this option,
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the computer will send out
a request for an IP
address. Then the DHCP
server will assign an IP
address from its pool and
deliver it to the computer.
Dynamic IP addressing is
the best choice because it
makes managing a
network a lot easier.
TCP/IP properties window for a
Windows computer.
You can also assign a computer with an IP address
manually, and this is called a static IP. A static IP is
where a user manually
assigns an IP address
for the computer. So
there is no need for a
DHCP server. This kind
of IP addressing is also
known as permanent,
because unlike dynamic
addressing, where the IP
address can change
automatically, a static IP
only changes if a user
decides to.
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When a computer is set to automatically obtain a
dynamic IP address, it gets the IP from a DHCP server.
But what happens if this computer cannot reach a
DHCP server? For instance, what happens if a DHCP
server goes down or if the connection to the server is
lost. If this happens then the computers that are
running Microsoft Windows 98 or later, the computer
itself will assign its own IP address.
DHCP server
169.254.0.0
Connection lost to the DHCP server. Windows
assigns itself with an IP address (APIPA).
This IP address will be in the 169.254.0.0 network. And
this type of self-assigned addressing is called APIPA,
which stands for automatic private IP address
assignment. Computers running Microsoft Windows
98 or later, do this so they can still be able to
communicate with other computers on the same
network that also have self-assigned IP addresses. If a
DHCP server later becomes available, the computer
changes its IP address to one that's obtained from a
DHCP server.
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TCP/IP Protocol
Suites
TCP (transmission control protocol) is one of the
main protocols used in a TCP/IP network. Now, this is
a connection oriented protocol, which basically means
that it must first acknowledge a session between two
computers that are communicating. And it does this by
using a three-way handshake. The first step is that a
computer will send a message called a SYN. Then the
receiving computer will send back an acknowledgment
message telling the sender that it has received the
message. And finally, the sender computer sends
another acknowledgment message back to the
receiver.
1. SYN
2. SYN ACK
3. ACK RECEIVED
TCP 3-way Handshake
Once this has taken place, data can be delivered.
Another important thing to remember about TCP is that
it guarantees the delivery of the data. So if a data
packet goes astray and doesn't arrive, then TCP will
resend it.
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Now, UDP (user datagram protocol) is very similar to
TCP. UDP is also for sending and receiving data, but
the main difference is that UDP is connectionless.
Which means that it does not establish a session and
does not guarantee data delivery. So when a computer
sends their data, it doesn't really care if the data is
received at the other end. And that's why UDP is
known as the 'fire and forget' protocol because it sends
data and it doesn't really care what happens to it.
Let me know if
you're missing
any of my data.
No problem, I
will.
TCP
Guarantees data delivery.
No, but this is
fun, please send
more!
Are you getting
all my data?
UDP
Does not guarantee data delivery.
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DNS stands for domain name system. Now this
resolves domain names to IP addresses. In the world
of networking, computers don't go by names like
humans do, they go by numbers. So if you type in a
web address in your web browser, DNS will transform
the name into a number, because all computers know
are numbers. So for example, when you type in
yahoo.com in your web browser, the DNS server will
search through its database to find a matching IP
address for that domain name. And when it finds the
IP, it will transform that domain name to the IP address
of a yahoo web server. So DNS basically works like a
phone book. When you want to find a phone number,
you don't look up the number first, you look up the
name first, and then it will give you the number.
yahoo.com
74.125.44.25
The DNS server will transform the domain name:
yahoo.com, into an IP address.
Network address translation or NAT is a service that
is typically used in routers, and this is used to translate
a set of IP addresses to another set of IP addresses.
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So for example, below we have a private network, and
it's using a set of private IP addresses internally. In the
middle we have the router with its public IP address,
and this router is running the NAT service. If a
computer in this network wanted to communicate over
the internet, it needs to translate its private IP address
to the internet’s public IP address. And this goes both
ways. If your computer on the internet wants to
communicate with a computer on this private network,
then the public IP address needs to be translated to the
private IP address for that computer.
10.0.0.1
10.0.0.2
67.158.212.121
10.0.0.3
A private network with computers using private
IP addresses, along with the router with its
public IP address.
FTP stands for file transfer protocol, and this is the
standard protocol that is used by web users to upload
and download files between computers through the
internet. So if a user wanted to make their files
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available to download to other users, all they would
have to do is simply upload their files to an FTP server
and then a user can simply download them. Now there
are a few ways to transfer files using FTP. You can use
your standard internet browser or you can use special
FTP software. It is also important to note that FTP is a
connection oriented protocol that uses TCP for file
transfer.
FTP server
A computer downloading files using FTP.
Now Secure FTP is just like FTP, except that it adds a
layer of security. The data using Secure FTP is actually
encrypted using secure shell during data transfer. So
no sensitive data, like passwords, are sent in clear
text.
SFTP server
A computer downloading files using SFTP.
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TFTP stands for the trivial file transfer protocol. And
this is a very simple transfer protocol. It is not used to
transfer files over the internet like FTP does. It's mainly
used for transferring files within the same network and it
does not provide any security during the transfer. And
unlike FTP, that uses the TCP protocol for file transfer,
TFTP is a connectionless protocol that uses UDP as its
transfer protocol.
TFTP server
A computer downloading files within a local area
network (not over the internet) using TFTP.
SMTP stands for simple mail transfer protocol. Now
this, as you might have guessed, is the protocol that is
used to send email. A good way to remember this is by
looking at the acronym SMTP, and translating that to:
‘sending mail to people’. SMTP uses the TCP protocol,
and as you know by now, it is connection oriented. So if
an email you send does not reach its destination, you'll
get that familiar mail delivery error in your mailbox,
informing that the email you sent, failed.
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SMTP is the protocol
for sending email.
Sending
Mail
To
People
A quick way to remember
what SMTP does.
Where SMTP is used for sending email, POP3 is the
protocol that is used for receiving email. Whenever an
email arrives at your mail server, you can retrieve it
using the POP3 protocol and download it to your
computer. The main characteristic about POP3, is that
all it does is grab the email from the mail server and
downloads the email to your computer. It does not sync
any email or folders from the mail server unlike IMAP4,
which we’ll talk about next. POP3 strictly downloads the
email. And typically when your email application using
POP3 retrieves the email from the mail server, no copy
of the email is left on the mail server, unless you specify
in your email application to keep a copy on the mail
server. POP3 is commonly used with email applications
such as Microsoft Outlook.
IMAP4 is another protocol that is used for receiving
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email. IMAP4 is similar to POP3 because they are both
used for retrieving email from a mail server, but IMAP4
has better features. With IMAP4 you can access and
manage your email on the server from your local
computer. So if you wanted to read your email and
keep a copy of it on the server, IMAP4 will allow you to
do just that. And unlike POP3, IMAP4 syncs your email
and your email folders from the mail server with all your
devices. And IMAP4 is also commonly used with
Microsoft Outlook.
POP3
Mail server
POP3 only downloads the email. Does not keep a
copy of the email on the mail server.
IMAP4
Mail server
IMAP4 syncs email and folders with all your
devices. Keeps a copy of the email on the
mail server.
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HTTP stands for hypertext transfer protocol. Now
this is probably the most widely used protocol in the
world today. HTTP is the protocol that is used for
viewing web pages on the internet. So when you type
in a web address, for example, google.com, you'll notice
that HTTP is automatically added at the beginning of the
address. And this indicates that you are now using
HTTP to retrieve this web page.
http://google.com
HTTP being used to retrieve the google.com webpage.
In standard HTTP, all information is sent in clear text.
Now, normally this would be okay if you were just
browsing regular web sites. But if you were at a website
where you had to enter sensitive data, such as
passwords or credit card information, then this would be
a problem as far as security. HTTPS stands for secure
hypertext transfer protocol, and this is HTTP with a
security feature. HTTPS encrypts the data that is being
retrieved by HTTP. So for example, if you wanted to go
to your bank's website to check your account, you
would notice that an ‘S’ will be added to the HTTP in the
web URL.
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https://bank.com
An 'S' has been added to http. This indicates
that secure HTTP is being used.
And this indicates that you are now using HTTPS and
have entered a secure website where sensitive data is
going to be passed, and that data needs to be protected.
Some other examples where HTTPS is used, would be
email servers and e-commerce (shopping) websites.
Telnet a terminal emulation program that is used to
access remote servers. It's a simple tool that runs on
your computer and it will allow you to send commands
remotely. And because it only sends commands and not
graphics, it's very fast. But the drawback is that it's not
secure. All commands are sent in clear text. So today,
telnet is mainly used to access devices within a local
network and not over the internet.
Now SSH or secure shell is a better alternative to
telnet. Secure shell protects the data from being
attacked or stolen as it's being transferred over a
network. So for example, if you were sending sensitive,
like a login or password, a potential hacker could be
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listening and steal the data. And that’s the reason for
secure shell. Secure shell acts like a secure tunnel that
forms around the data transfer and protects it from
potential threats.
SSH secure tunnel
Hacker
SSH acts like a secure tunnel, protecting the data from
being stolen.
SNMP or simple network management protocol is
used for network management. It's basically used
network devices such as routers, printers, and servers.
Ports
Now a port is a logical connection that is used by
programs to exchange information. And these ports
have a unique number that identifies them. The number
ranges from 0 to 65535, but for the exam you only need
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to know a few of them. So below is a chart of the ports
that you need to know for the exam. Some of these
ports are very common and are used every single day,
such as port 80, which is used for bringing up web
pages on the internet. Another one is port 443, which is
used for logging into secure web pages that require a
login and password. And another common one is port
25, and this is used for sending email from an email
application such as Microsoft Outlook.
Port numbers with their associated service.
Internet Access
Technologies
DSL stands for digital subscriber line. And this is a
popular technology that is used by homes and
businesses to access broadband data over the internet.
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DSL can carry both voice and data at the same time. It
has a DSL modem that uses common telephone lines to
carry its data. It’s a high-speed connection that is much
faster than your regular dial-up modems.
DSL carries voice and data over normal telephone lines.
There are a few different forms of DSL, and one is called
ADSL, which stands for asymmetric digital subscriber
line. This is called asymmetric because the download
speed is considerably faster than the upload speed.
This type of DSL is typically used in homes and is the
cheapest form of DSL.
SDSL stands for symmetric digital subscriber line.
And as the name implies, the download and upload
speeds are the same. This type is typically used in
businesses.
VDSL stands for very high bit DSL, and this is a very
fast form of DSL. It has download speeds of over 50
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Mbit/s over a copper wire. But because it uses copper
wire, it's only made for short distances. For long
distances, it can also use fiber optic cable.
Another popular technology that is used to access the
internet is broadband cable. Cable is by far
becoming the technology of choice by many homes to
access the internet. It uses a cable modem with an
attached coaxial cable, which provides a link to the
internet service provider. Like DSL, cable is very fast,
with speeds of over 50 Mbit/s. Broadband cable is
typically provided by the same provider that provides
cable television to their customers.
Cable modem
Coaxial cable
POTS/PSTN stands for plain old telephone service
and public switched telephone network. And these
are just your plain old telephone lines. And these are
slowly becoming obsolete by people who use the
internet because of their slow speeds. So if you have
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ever used a high-speed internet such as broadband,
you will never go back to using a slow speeds of 56 K,
which is the speed of a standard dial-up modem.
However telephone lines do have an advantage, and
that is that they are basically everywhere and they are
fairly cheap to use.
Plain old telephone lines
ISDN stands for integrated services digital network.
This is an international standard for digital transmission
over ordinary telephone lines. In order to use ISDN,
users had to install ISDN modems. This was a
significant improvement in speed over the standard
modem, because a standard modem sends data at a
maximum speed of 56 Kbps, but ISDN sends data at
128 Kbps. However ISDN never really caught on,
because of the faster speeds of DSL and cable.
Satellite communication is pretty expensive and it's
mainly used where no other services are provided, like
phones, cable, or DSL. But because of the increasing
availability of these other options, satellite is rarely
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used. The speed of satellite has increased throughout
the years, with speeds maxing out around 15 Mbit/s,
with only a fraction of that in upload speeds.
Another method of connecting to the internet is by
using mobile hotspots. Mobile hotspots are portable
devices that use cellular networks to connect wireless
devices to the internet. So if there are wireless
devices within 30 ft. of a mobile hotspot, they can join
it and have access to the internet. Mobile hotspots
come in two forms, they will either be a free-standing
device like you see below, or they can come as a
feature built into a smartphone. And mobile hotspots
are available through cell phone carriers such as
Verizon, AT&T, T-Mobile, and Sprint.
Mobile hotspot
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Network Types
PAN stands for personal area network. And this is a
type of network that is used on a personal level. It's a
small network that is basically used for connecting
things like mobile phones, PDAs, and laptops to each
other using bluetooth. PANs are generally used for
transferring small files, such as music, photos, calendar
appointments, and so on.
Example of a PAN
(personal area network)
LAN stands for local area network. A local area
network is a group of devices such as computers,
servers, and printers, which are basically located in the
same building. In other words, in close proximity to each
other. The most common type of LAN is an Ethernet
LAN, where two or more computers are connected to
CAT5 Ethernet cables using a switch.
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Example of a LAN (local area network)
MAN stands for metropolitan area network. This is a
larger network than a LAN. It's a network that spans
over several buildings in a city or town. MAN's are
typically connected using a high-speed connection such
as fiber optic cable.
Example of a MAN (metropolitan area network)
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Finally, there is the wide area network or WAN. A
WAN it when is the largest type of network. It's a
network that spans over a large geographical area, such
as a country, continent, or even the entire globe. A good
example of a wide area network is the internet.
Example of a WAN (wide area network)
Networking Tools
If you're already a network administrator, then the most
common tool that you've probably used is the wire
crimper. This tool is used to make custom length
network cables. It crimps adapters, such as the RJ-45,
to twisted pair cables. So after you have attached your
RJ-45 adapter to your cable, you just place it into the
crimper, give it a squeeze, and the cable is done.
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Wire crimper
A punch down tool is a tool that resembles a
screwdriver. And this is simply used to connect or
punch wires into a punch down block.
Punch down tool
Another network tool is a media
tester. So after making a custom
length cable using your wire
crimper, it's a good idea to test the
cable to make sure it's wired
correctly. So you would just
connect both ends of the cable
into the tester, and then the tool
will check the cable for you.
Media tester
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The plastic shielding around a network cable must
be removed in order to crimp a connector. This is
done by using a cable stripper. The cable is then
inserted into the tool and then the outer plastic
shielding is removed.
Cable stripper
A multimeter is a device
that is used to test electrical
circuits. It's a popular tool
that is used for many
different trades. It can
measure voltage,
resistance, current, and
continuity, just to name a
few. And it comes in both
analog and digital versions.
Multimeter
A tone generator is also known as a Fox and
Hound. It's a tool that is used for locating cables from
one end to the other. So for example, if you suspect
that you have a bad cable that was grouped with a lot
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of other cables, and that group was stretched over a
long distance, it would be very difficult to isolate one
end of the cable from the other. So that's where a tone
generator comes in. So you just connected the tool at
one end of the cable, and then it would generate a tone
through the cable, where the other part of the tool
would detect the sound and pinpoint the cable.
Tone generator generating a tone through a
cable to pinpoint it at the other end.
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SOHO Routers,
WIFI Encryption
Next, we're going to talk about SOHO routers, which
stands for a small office home office router. And
these are your
common inexpensive
routers that are used in
homes and small
businesses. These are
fairly easy to set up,
but if you don't
configure the router
correctly, you will not
have access to your
SOHO router
network or the internet.
To set up and configure your SOHO router, you need
to go to the router's built-in configuration web page. So
you would just open up a web browser and in the
address field, you would type in the router's IP
address. So, for example, our router has an IP
address of 192. 168. 2. 1. And once you type that
in, you press enter on your keyboard and now you're
in.
192.168.2.1
Router's IP address
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So here is an example of
the configuration page for a
Cisco SOHO router. And
this is where you would set
up the router with custom
settings to make it work for
your particular network. So
for example, like most
SOHO routers, this one has
a DHCP server built into it.
And as you recall, a DHCP
Router's configuration
server automatically assigns
page
an IP address to each
computer on your network,
because all computers need an IP address to function
on a network. So by default, the DHCP server is
enabled but if you want to, you can disable the DHCP
server by clicking 'Disabled' and then just save your
settings.
DHCP settings for the router.
Also in a router's web page, there are the wireless
settings. Now in here you can configure the wireless
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settings for your network. So for example, you can set
the SSID which stands for service set identifier,
which is basically the name of your wireless network.
The SSID is shared among all wireless devices and it's
customizable, so you can name it whatever you want.
And as you can see below, this SSID is called 'My
Wireless'.
Wireless settings for the router.
So as an example, when a laptop scans for a wireless
network to join. And if the laptop is in the vicinity of this
router, the laptop will see the router's SSID broadcast,
called 'My Wireless', and if it has the proper credentials,
it can join the network.
My Wireless
My Wireless
My Wireless
My Wireless
My Wireless
Router broadcasting its SSID
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You can also set the channel for your wireless network.
Channels are used to avoid interference with other
wireless networks nearby, or even wireless devices
such as cordless phones. So if you are experiencing
any connectivity issues to your wireless router, there
might be interference with another nearby wireless
network or device, that's operating on the same channel
as yours. So, in this case, you can try changing to a
different channel and see if it solves your problem.
Wireless channel settings page
If you click on the wireless security section, you can
configure the security of your wireless network (graphic
below). So here, you can choose to disable security
and have your wireless network wide open. Or you can
password protect your wireless network with one of
these security modes. And as you can see, this router
supports the following security options, such as WEP,
WPA, and WPA2.
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Wireless security options for the router
WEP or wired equivalent privacy, is one of the
security protocols that are used for wireless networks.
And as its name implies, it's meant to supply the same
security to wireless networks, as it did for wired
networks. But this turned out not to be the case. After
a time, it was found out that the 40-bit encryption key
that WEP used, was not secure and it was easily
hackable. So a better security protocol was needed for
wireless.
WEP wireless security
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WPA or Wi-Fi protected access, is another wireless
security protocol that was developed to solve the
security problems of WEP. WPA is far better than WEP
in two ways. First, it uses a stronger encryption method
using TKIP, which stands for temporal key integrity
protocol, which dynamically changes his keys as it's
being used. This ensures data integrity. And secondly,
WPA uses EAP which verifies authorized network
users.
WPA wireless security
Building on the security of WPA. WPA2 was developed
to provide even stronger security than WPA. And it
does this by requiring the use of a stronger wireless
encryption method. While WPA uses temporal key
Integrity protocol for encryption, which is known to have
some limitations, WPA2 uses CCMP (counter Mode
cipher block chaining message authentication code
protocol) for encryption. And CCMP is more secure
because it uses an enhanced data cryptographic
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encapsulation mechanism. And since 2006, WPA2 is
available on all certified wi-fi hardware.
WPA on steroids.
WPA2 wireless security
Another wireless security protocol is WPS. WPS stands
for wi-fi protected setup. WPS was designed for
users who know little about wireless networks, to make
it as easy as possible for them to join a secure wireless
network. So here's the WPS configuration page for our
router.
WPS wireless security settings
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And as you can see, there are three different WPS
methods that you can use to join this wireless network.
So you could use method 1 if your client has a wi-fi
protected setup button. You would just press that
button on your device, then within two minutes you
would press the WPS button here on this page, or you
can just press that physical WPS button on the router
itself, and then you'll be connected.
Method 1 of WPS wireless security settings
You can also use method 2 if your client has a WPS pin
number. You would just enter that number in the field
below, and then press register.
Method 2 of WPS wireless security settings
And finally, you can use method 3 if your client asks for
the router's pin number. So you would just enter the
router's pin number that's displayed on this page, and
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enter it into your device, and then you'll be connected.
Method 3 of WPS wireless security settings
So as stated before, WPS is the easiest way to join a
wireless network. And a lot of manufacturers are
building their wireless products with WPS, to make it as
simple as possible for their customers to join their
device to a wireless network.
Another wireless security feature is the MAC filter.
Every wireless adapter has a MAC address. A MAC
address is a hexadecimal number that uniquely
identifies each device on a network. And with the
wireless MAC filter, you can either prevent or permit
access by using the device's MAC address.
Wireless MAC filter settings (devices prevented)
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So in the example above, once we enable the MAC
filter, we can choose the option to prevent devices that
are listed above from accessing the wireless network.
So all of these devices listed above are now blocked
from joining the network.
Or the other option, we can choose the permit option.
And this will allow only the devices listed below access
to the network.
Wireless MAC filter settings (devices permitted)
There's also what's called the DMZ, which stands for
demilitarized zone. The DMZ allows a designated
computer on your network to be fully exposed to the
internet. And it does this by the router forwarding all
ports at the same time to the designated DMZ computer.
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Protected
computers
DMZ
computer
So while some computers here on our network are
protected inside the firewall, the DMZ computer is
outside the firewall and is not protected. The DMZ is
typically used for testing purposes. So if you just set up
a computer that you want to be accessed from the
internet, and if you're having a problem configuring a
firewall and applications so that it can be accessed from
the internet, you can simply bypass all firewall security
and put the computer in the DMZ temporarily to make
sure everything is working until you can pinpoint the
problem you are having. For instance, you could be
having a problem with a firewall setting. It's also
important to note, that the DMZ computer should be
assigned a static IP address and not automatically from
a DHCP server.
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Network Utilities
The ping command is the most widely used of all
network utilities. It's a tool that is used to test issues
such as network connectivity and name resolution. So,
for example, to ping a host IP address, you would open
up a command prompt and you would type the word
'ping', along with an IP address, and then press enter.
Then the ping utility will send out four data packets to
the destination IP address you chose.
Successful ping. 4 packets sent and 4
packets received.
Then the destination will send the data packets back to
us, as a reply. These replies are called echo reply
requests. These replies inform you about what's
happening with the destination host we pinged. For
example, if we received a reply then that means that
there is general network connectivity between us and
the destination. But if we did not get a reply, then that
means that there is no reply from the host and it could
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mean that there is no network connectivity between
your computer and the IP address that you're trying to
ping.
Unsuccessful ping. 4 packets sent and 0
packets received.
But if we pinged the host and we got a message that
says 'request timed out', then that could mean that the
host is down, or that it's blocking all ping requests. Or
after we pinged, and we get a message that says
'destination host unreachable', then that message is
coming from a router and it means that a route to the
destination cannot be found.
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Destination host unreachable means that the
route could not be found.
The ping command can also be used to test a DNS
name resolution issues. For example, before we used
the ping command with an IP address, but we could also
use it with a domain name. For example, we could type
'ping' then the domain name 'yahoo.com'. So if by
pinging the domain name and if we got the same
successful result by typing the IP address, then this
would indicate that the name resolution by DNS is
working fine. But let's just suppose that pinging the
domain name failed. The next step will be typing the IP
address instead. So if by typing the IP address, and if
the ping was successful this time, then we now know
that we are having a problem with DNS.
Pinging domain names instead of IP
addresses are used to test DNS issues.
The ping command can also be combined with other sub
commands called switches. And switches are used to
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alter the parameters of the ping utility. You can view a
full list of these switches by typing ping /?
The ping sub commands
Our next utility is called tracert which stands for a
traceroute. And this is used to find out the exact path a
data packet is taking on its way to the destination. So
for example, let's go ahead and trace the route from our
computer to another computer.
Traceroute example
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So at a command prompt, we would type 'tracert' space
and then the IP address and press enter. Then the data
packet will find its way to the destination, and each time
it reaches a router on its path, it will report back
information about that router, such as the IP address
and the time it took between each hop. So the tracert
utility is a great tool that can be used to pinpoint where a
problem lies on a network if the data packet cannot
reach the destination.
The nbtstat utility is used to resolve NetBIOS names to
IP addresses. So at a command prompt, just type in
'nbtstat' with a -s switch, and below is an example of the
result. The nbtstat utility is probably the least common
utility that you would ever use.
Nbtstat utility used with a -s switch
Our next utility is called netstat. Netstat is a very useful
tool and it's used to display current network connections
to your computer. So in our example here, we can
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visually see that our computer is currently
communicating with an FTP server, and two HTTP
web servers.
64.86.142.153 http
FTP
Our computer
199.181.132.250 http
Netstat utility showing 3 current connections
to our computer.
And we can verify this by using the netstat utility. So at
a command prompt, we type 'netstat', and in this case,
we're going to use a -a switch, and then press enter.
Now in our display above, we can see the two http
servers and the FTP connection. So even if you're not
sure what connections your computer currently has, you
can use the netstat utility to find out. And in addition to
connections, it also displays which ports are open and
listening for a connection.
The ipconfig utility is very common. This utility is a
powerful tool that's used to display the network
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configuration for our computer. And this information can
be used for problem-solving. So for example, if we open
up a command prompt and type in 'ipconfig /all', this
will display the full TCP/IP configuration for our
computer. Such as our computer name, MAC address,
IP address, default gateway - which is the router, DNS
servers, and so on.
The Ipconfig utility can be used to display the
full TCP/IP configuration for a computer.
By using this information we can find solutions if we are
experiencing problems. For example, if we had a
problem with our IP address, we can see from this
information that DHCP is enabled, which means that this
computer is getting its IP address from a DHCP server.
It also tells us the IP address of the DHCP server. It
also tells us the IP address of the DNS server. So if we
are experiencing any problems browsing the internet
with domain names, then there might be a problem with
the DNS server itself.
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Using the ipconfig utility by itself displays the IP address,
subnet mask, and default gateway. But using this utility
when combined with subcommands, called switches,
changes the output slightly. So for example, when we
use ipconfig /all, which we just used in our previous
illustration, displays the full TCP/IP configuration for our
computer. When we use ipconfig /renew, this releases
and renews the lease of the IP address given to us from
the DHCP server. And ipconfig /release, releases the
IP address, but does not renew it.
To see a complete list of all the switches that can be
used with ipconfig or any command utility, just type the
name of the utility along with a /? - and that'll show you
all the switches that are available for that specific utility.
Ipconfig /?
Example of a utility using a subcommand to display all
switches that are available.
Similar to the ipconfig utility that used in Windows, there
is also the ifconfig utility. The ifconfig utility is a
command that's used in Unix and Linux operating
systems. It displays configuration information from the
network interface card, such as the IP address, subnet
mask, how many packets it has received and sent, any
errors, and so on. And like ipconfig, it can also be
combined with switches to alter the output.
And our last utility is called nslookup. This name is
short for name server look up. And this utility is used to
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look up DNS information. So for example, at a
command prompt, if you type in nslookup, along with a
domain name such as yahoo.com, the result will give
you the information for the Yahoo domain. And the dig
command is the Unix version of nslookup. It does the
same thing.
Example of the nslookup utility
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