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EM TROUBLESHOOTING 4.0

UNIT 05_ Basics of Computer Networking and Setting up a Local Area Network (LAN)


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Introduction and Defnitions

In general, the Units have focused more on learning practical skills rather than learning the theory behind any

of the skills discussed. This trend will continue in this Unit. However, some background understanding of the

terminology used when working with networks will help telecentre managers to move forward through this

module smoothly. Therefore some of this basic information is covered through the denitions and abbrevia-

tions that are explained below.

Computer Network.A computer network is a group of computers connected for the purpose of communi-

cation or sharing information, software or hardware. They can be connected through a variety of means

including both wired and wireless.

The Internet.This is the largest computer network in the world! It is a constantly growing connection of

computers and networks around the world, and is used to communicate and share information in many

ways, some of which will be discussed later in this module.

ISP (Internet Service Provider).This is the organisation or company that connects an individual computer

or a computer network to the Internet, therefore allowing for communication and collaboration with mil-

lions of other computers and their users.

Firewall.A rewall is a tool that is designed to protect a computer or a network from security threats (such

as malware or unauthorized access) from the Internet. A rewall can be a piece of software found on an

individual computer, or a hardware device incorporated into a computer network.

IP Address.An Internet protocol (IP) address is a four part number, written with decimal points (full stops)

separating each part. An example IP address is 192.168.0.200. An IP address is rather like a phone

number for a computer or networking equipment. Computers on the Internet that know each others IP

addresses can communicate with each other. Networking equipment (such as routers and server comput-

ers) keeps track of these IP addresses as they facilitate connections between computers. Every computeron the Internet or on a network using TCP/IP (described below) must have its own IP address. Due to the

ever expanding numbers of computers connected to the Internet, a new system with six part IP addresses

(called IPv6) has been developed and will eventually become the standard on the Internet.

TCP/IP. TCP/IP is short for Transmission Control Protocol/Internet Protocol. These protocols (or rules) de-

ne how devices (such as computers and routers) communicate with each other. TCP/IP determines the

best path for information (data) to travel from one device to another. TCP/IP will break up data into small

packets that are sent separately and then reassembled upon arrival.

DHCP. The Dynamic Host Conguration Protocol (DHCP) is a set of rules used by a DHCP server (a

server computer, a rewall, a modem or a router) to allocate IP addresses to computers on a local net-

work or the Internet. Using DHCP is typically easier than having a telecentre manager or computer users

assign and keep track of IP addresses. In most small networks the router acts as the DHCP server.

MAC Address. The Media Access Control (MAC) address is also known as the physical address for any

device (such as a network interface card or a wireless network adapter) that connects a computer to a

network. Every network device has its own unique MAC address that (like a serial number) cannot be

changed and is useful for identifying that device when it is a part of a network.


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01_ Basics of Computer Networking

Computer networks come in a variety of types and designs, depending on the size and needs of an organiza-tion. Telecentre managers who are interested in understanding all of the options in detail are encouraged to

take a full course on computer networking.

For the purposes of this Unit, however, only the types and designs of networks that a telecentre manager is

most likely to encounter or use will be discussed. When networking the computers in a single room or building

(or perhaps a group of closely associated buildings), the network is called a local area network or LAN. Set-

ting up a LAN allows the computers in the network to communicate between each other internally (called an

intranet). This can be very useful for sharing information and resources (such as printers), even if the network

is not connected to the Internet.

If a LAN is comprised entirely of computers communicating wirelessly, it is referred to as a wireless local area

network or WLAN. There are several names used to describe networks that are geographically larger than a

LAN or WLAN. For example, a campus area network (CAN) describes a network that encompasses several

nearby buildings. The term metropolitan area network (MAN) is used to describe a network that connects

two or more LANs in the same city. A wide area network (WAN) describes a connection between two or more

distant LANS, such as two locations of the same company in different cities. The largest network of all is the

Internet. The Internet is the result of connections between computers and networks all over the world.

When connecting computers with wires to form a LAN, the pattern (called a network topology) is important to

consider. In the diagrams shown here (Figure 1) the dots represent computers or other devices connected to

a network. The lines represent cables connecting the devices.

When choosing a topology, it is important to consider what will happen if one of the cables fails. In ring, line

and bus topologies, a failure in a cable can cause many dependent computers to lose a connection. There-

fore, star topology is much more common and reliable in telecentres, even though it requires more cable. Thedot in the middle of the star is either a server or a router (both terms are explained later), sharing information

between the other computers shown. Tree and mesh topology are options to consider as well.



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02_ Networking Equipment

The equipment required to set up a computer network varies depending on the type, size and purpose of a

network. If a networks main purpose, for example, is to connect a group of computers to the Internet, then

equipment will be needed to receive the Internet signal from the ISP. This equipment varies widely and was

described briey in the previous section. Other common equipment is described here.

Router. A router is a device used to connect two different networks. In

most cases the two networks it connects are a LAN and the Internet (via a

modem or other device that receives an Internet signal). Routers can also

direct Internet trafc to various computers on the LAN. This allows many

small networks to operate without a server (described below). Routers

have varying numbers of ports that allow for connections to computers or

switches.

Wireless Routersare routers that also act as wireless access points (de-

scribed below).

Cable. Unless a network is entirely wireless, CAT-5 (category 5) cable (also

known as Ethernet cable) is required to connect all devices on the network.

CAT-5e (category 5 enhanced) and CAT-6 are recent improvements on

CAT-5.

Switch.A switch is a device used to connect several computers at one

point. This is useful for star, tree and mesh network topologies, and when

the router on a network does not contain enough ports to connect all of the

computers or other devices on the LAN. Switches also control network traf-

c by directing specic data only to the computer that requested it. Before

switches were developed networks used hubs to connect computers, but

these did not control network trafc.


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02_ Networking Equipment Continued

Wireless Access Points. Many computers contain wireless adapters that allowfor connections using radio signals instead of cables. In order to transmit and

receive these radio signals, a network needs either a wireless router or a wire-

less access point. A wireless access point performs the same role on a wireless

LAN (WLAN) as a switch does on a LAN. A WLAN that covers a wide area may

need multiple wireless access points in order to have all computers in signal

range. All wireless computer devices use the WLAN standard (called 802.11)

for transmitting and receiving. However, this standard has been rened and

improved over the years from 802.11b to 802.11a to 802.11 g. The newest stan-

dard (still in development in 2009) is 802.11n. New wireless equipment should

be compatible with the b, g and n standards.

Cards and Adapters.Each computer that participates in a LAN needs to havehardware that allows it to connect to the network. Most computers have a built

in network interface card (NIC, also called an Ethernet card) that allows it to

connect to CAT-5 cables via the Ethernet port. For wireless connections, a wire-

less adapter is needed. Most laptop computers have internal wireless adapters,

but some older laptop computers and many desk top computers do not. For

these situations, the easiest solution is to buy an external wireless adapter that

plugs into the computers USB port.

Server.A server computer is used on a network to share information and direct trafc to other (client) comput-

ers. Many small networks do not need servers.

Shared Hardware.One possible use of a LAN is to network peripheral hardware so that it can be shared

amongst all of the computers on the network. Printers are commonly networked and will be discussed later in

this Unit. Other hardware that can be networked includes scanners, webcams and hard drives (for backing up

data).

It is worth noting that all networking equipment has its own operating speed, which controls the maximum

speed of communication within a LAN. Replacing older and slower equipment can improve network speed.

due to the improper shut down.


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03_ Setting Up a Simple LAN

Imagine that an ISP has just set up an Internet connection for your telecentre. Whats next? Probably thetelecentre manager will want to set up a simple LAN and then use it to connect the computers to the Internet.

This is can be done simply, as explained below, and does not need to involve a server computer since the

router can direct Internet trafc.

The telecentre manager will need to determine in advance whether to make the network wired, wireless or a

combination of the two. Wireless networks are simpler to set up but more attention needs to be paid to secu-

rity with wireless networks. In addition, not all desktop computers come with wireless adapters.

Imagine that a broadband Internet connection has just been installed at your telecentre. Here are the steps for

setting up a small LAN to connect computers to the Internet.

Step 1: Install a router.This is as simple as plugging it into an electrical outlet, and then using a CAT-5 cable

to connect it to the Internet source. The Internet source will vary with the type of connection. For a WiMaxconnection, for example, you might be connecting directly to an antenna or to a modem connected to the

antenna.

Step 2: Connect wired computers to the router.If the router has enough ports on the back for all of the com-

puters on your network, you can attach them directly using CAT-5 cable. The router will act as the center of

a star network. If the router does not have enough ports, move on to step 3. You may also need to install

the software that came with the router onto one of the networked computers and use it to complete the

initial setup for the router.

Step 3: Connect a switch to the router. This should be done if the router does not have enough ports for all

the computers on your network, or if a group of computers is in another room. The switch connects to one

of the ports in the router via a CAT-5 cable, and also will require an electrical outlet. Computers then con-

nect to the switch, forming a star network.

Step 4: Connect wireless computers to the router. If you have a wireless router and computers with wireless

adapters, connect each computer individually to the router by using the tools in their operating systems for

network connections (for Windows computers these can be found in the control panel). If the router (or the

switch) is not wireless or if wireless access is needed in a different location, move on to step 5.

Step 5: Connect a wireless access point to the router. If additional wireless access is needed, scout out the

best location for this access (so that as many computers as possible are in range). Then connect the wire-

less access point to one of the ports in the router via a CAT-5 cable.


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03_ Setting Up a Simple LAN Continued

01_ Working with CAT-5 Cable

In the above section for setting up a simple LAN, CAT-5 (or the faster CAT-5e) cable plays a major role.

It is needed to make connections to and from the router as well as any switches, wireless access points

and wired computers in the LAN. While CAT-5e patch cables in various lengths can be purchased, it will

be more economical for a telecentre manager to buy a spool of CAT-5 cable and cut it into patch cables

of the desired length. The telecentre manager will need to attach RJ-45 connectors to each end of the

cables cut (a process called terminating). A crimping tool is required for this procedure. It is important to

note that CAT-5 cables should not be more than 100 meters in length, or the signals they carry become

degraded. In addition, a telecentre manager should be aware that after repeated handling some cables or

RJ-45 connectors will fail. The tip box here shows the steps for terminating a CAT-5 cable.

Tips for Terminating a Cable

1. Take a segment of CAT-5 (or CAT-5e) cable and cut it to the desired length. If you arent sure the length

you need always err on the side of extra length. You can shorten a cable later but you cant make it

longer again!

2. Gently cut around the outer plastic covering of the wire, 1.2 cm from one end of the wire. You can use

the cutting blade on the crimping tool to do this (see Figure 2). Make sure, however that you do not cut

the plastic coating on the inner wires. Strip away the end section of the outer plastic cover and inspect

the inner wires to make sure they are in good condition. If they are not, cut off the damaged section of

cable and start over.

3. Spread out the individual wires and order them according to colors as shown below (from left to right):

White/Orange, Orange, White/Green, Blue, White/Blue, Green, White/Brown, Brown

4. Once the wires are properly aligned, keep them neatly aligned and close together while you cut off the

uneven ends of the wires using the cutting blade on the crimping tool (see Figure 3).

5. While keeping the wires properly aligned, insert them into an RJ-45 connector. There are 8 small

canals in the connector and one wire will t into each canal. Make sure that wires are aligned with the

white/orange wire on the left and the golden pins of the RJ-45 connector on top. The plastic tab will be

on the bottom.

6. Insert the assembled connector into the crimping tool (there is only one way it ts) and then press down

rmly. This causes the pins to be pushed into the wires, making electrical connections.

7. Repeat steps 2 - 6 on the other end of the cable.

8. Test the cable. The easiest way to do this is to use it to connect a computer to the Internet. Use it to

replace a cable in a set-up that you know works perfectly.


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03_ Setting Up a Simple LAN Continued

02_ Working with IP AddressesFor most telecentre managers, the simple network set up should be plug and play. This means that after

the telecentre manager completes the physical set up, the network works automatically. The most impor-

tant factor that allows this to happen is that the router acts as a DHCP server. This means that the router

assigns IP addresses to the computers on the network, thus allowing these computers to share informa-

tion amongst themselves and with other computers on the Internet.

In most cases the IP addresses that the router assigns will be dynamic, which means that they change

after some time. The router leases out a particular IP address for a specic period of time, often 24 hours.

Since there are a limited number of IP addresses available for the router to use, this system prevents the

IP addresses from being used up by computers that are not often on the network. The telecentre manager

can view the IP address for a computer using a variety of methods, described in the tip box here.

Note that IP addresses for computers on a LAN will always begin with 192.168. This is the range of ad-

dresses allotted for use on private networks. When a computer on the LAN sends information out to the

internet, it passes through a rewall (usually part of the router) and the rewall attaches a different (public)

IP address to that information.

Tips for Finding a Computers IP Address

Several methods are shown below. Which you choose depends on your computers operating system.

Method A: On a Windows computer, choose Start Control Panel Network and Internet. On a Win-

dows XP computer then choose Network Connections and double click on the active Internet connec-

tion shown. On a Windows Vista computer then choose Network and Sharing Center and click view

status on the active Internet connection shown. Then click on Details to see the IP address.

Method B: Open up the Command Prompt window on your computer. Command Prompt is a way of

entering in commands directly (not through the typical graphic interface). On a Windows computer the

command prompt line can be found in Start All Programs Accessories Command Prompt. In

the Command Prompt window enter the text ipcong/all.

Method C: On an Ubuntu or Linux computer, open the Command Line by holding down the Ctrl and Alt

keys while pressing down the F1 key. Then enter your username and password if prompted to do so.

You can also access the Command Line by selecting Applications Accessories Terminal. Then

enter in the text ifcong.


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04_ Setting Up a Network or Shared Printer

As mentioned previously, one advantage of having a LAN is to allow for shared printers. Buying and network-ing a single printer for shared use is much more cost effective than buying printers for each computer (or

requiring users to transfer documents to the computer with the attached printer). It is also more efcient than

having a single non-networked printer and requiring all users to bring their documents (via ash drive, disk or

email) to the attached computer.

Equipment. There are several equipment options for setting up a networked printer. The simplest of these is

to buy a network printer. Network printers are available in both wired and wireless models. The wired net-

work printer would be connected via CAT-5 cable to the router or switch. If a network printer is not available

or affordable, a second option is to purchase a print server. This small device attaches to a printer and then

attaches to the network as above. Print servers are available in both wired and wireless models. Before pur-

chasing a print server, a telecentre manager should make sure that it has ports (such as USB or parallel) that

are compatible with the existing printer. A third option for networking a printer is to attach a printer to a com-

puter that is attached to the network. This computer then can share that printer on the network and managethe print queue for that printer. The methods for sharing a printer and printing to a shared printer depend on

the computer operating system in use. Information can be found by searching a computers help le for share

printer.

Communication. Once a computer has been attached to the LAN (via the rst or second options above), it

should automatically be assigned an IP address by the router. With this IP address, a computer user can print

directly to the printer from any computer on the LAN. Before printing the rst time, each computer will need

to add the printer to its list of available printers. For Windows computers this can be done through the Add

a Printer wizard. This tool can be found through Start Control Panel Hardware and Sound (or Print-

ers and Other Hardware) Printers. In most cases, this wizard will help the user nd the printer through

browsing. If the printer is not automatically found, however, the user may need to enter the IP address for the

printer. If this is necessary, the IP address can be found by printing a conguration page at the printer.


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05_ Troubleshooting a Network Failure

One of the more frustrating experiences for a telecentre user is to get set up to check email or search for

information on the Internet, only to discover that there is no Internet service. Network failures like this can

be external (due to a problem with the ISP or the connection to the ISP) or internal (due to a problem with

the LAN). A user can also experience network problems that are due to hardware or software issues with an

individual computer. Once it is determined whether the problem is with a particular computer (can other users

reach the network?) or network-wide, then troubleshooting can begin.

01_ Failures with a Particular Computer

If a particular computer cannot connect to a LAN or the Internet when other computers in the same area

can, the rst step is to determine if the specic location is the cause of the problem. For example, if the

computer is connecting wirelessly is the signal particularly weak there? Moving the computer to a differ-

ent location where another computer connected successfully would test this theory.

If connected by cables, the telecentre manager could try swapping patch cables with one that is known

to work. Once a problem with the patch cable has been eliminated, the next step would be to swap the

troubled computer with one that connected successfully in another location. If the new computer cannot

connect in this location, then the problem could be with connectors, switches or router ports that the com-

puter work station ultimately connects to. If the swapped computer can connect, however, the telecentre

manager has determined that the problem is with the individual computer and not with the location. In this

case the tip box here (above) gives some good troubleshooting suggestions.

Tips for Troubleshooting a Computer that Wont Connect to a Network

1. If the operating system has network diagnostic tools, run these to see if the computer can x the prob-

lem itself. For a Windows computer, follow the steps in the tip box above (Method A) to view a network

connection and then click on the Diagnose box. Also notice whether or not the computer is sending or

receiving any packets from the network. If the network diagram shows some packets being receivedgradually, then the connection is just working slowly.

2. Try getting a new IP address. For a Windows computer go to the command prompt line (see the tip

box above) and type and Enter ipcong/release and then ipcong/renew.

3. Restart the computer. This often will x temporary problems with hardware or software.

4. Use the Device Manager, which can found on many Windows computers (for Windows XP go to Start

Control Panel System Device Manager). If a network device has a (hardware) problem, a

warning symbol will be displayed next to it, and double clicking on that device would give details and

suggested remedies for the problem.


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05_ Troubleshooting a Network Failure Continued

02_ Failures with an Entire Network

In some situations, no computer on a LAN can access either the local intranet or the Internet. In these

cases, it is helpful to try and distinguish between the two problems.

For a Windows computer, the Network Connections or Network and Sharing Center (see the tip box)

shows the status of a connection, including whether it is local only or local and Internet. The lights on the

front of a router can also be used to indicate whether or not it is connected to the Internet. Another useful

diagnostic tool is to use a computer on the LAN to ping various devices on the LAN and see which ones

can be reached. Pinging means sending a packet of information and requesting a packet in reply. The tip

box here describes how to ping.

Tips for Pinging Networked Devices

Pinging is the process of sending a packet of information over a network and requesting a reply. Themain requirement for pinging is that you know the IP address (or web address) of the device you are

going to ping. Below are the steps to take when using pinging as a part of troubleshooting.

1. Open up the Command Prompt (or Command Line for Ubuntu) window on your computer.

2. To ping any device from a Windows computer you type ping then a space then the IP address for

that device. For computers with the Ubuntu operating system, you type ping -c 4 then a space

then the IP address for that device. The standard address (127.0.0.1) is used for a computer to re-

fer to itself. So you would type ping 127.0.0.1 or ping c 4 127.0.0.1 to ping your own computer.

Once you enter the command, the computer will send packets and report on whether replies were

received and how much time elapsed.

3. Next try to ping the router for your LAN using the procedure above. Usually the IP address for a

router is 192.168.0.1. If this is not correct, check your routers users manual.

4. Next try to ping the server computer or another computer on the LAN. Use the tip box in section3.1.3 to nd the IP addresses for these computers.

5. Finally try to ping an external website. You can use the IP address for that website if you know it, or

just enter the web address. For example: ping www.google.com or ping c 4 www.google.com.

Once it has been determined that the problem is not with the LAN but with the Internet or the Internet con-

nection to the router, the telecentre manager now has a narrower range of possibilities to address. The

rst step to take in these instances is to make sure the router is functioning properly.

The telecentre manager should reboot the router (turn it off or unplug electricity to the router, wait a few

seconds then turn it on again) rst to see if that solves the problem. If not, the lights on the front of the

router (along with the router users guide) can be used to indicate whether or not it is functioning properly.

The telecentre manager can also try rebooting the modem, WiFi receiver or any other devices used for

receiving the Internet signal. A telecentre manager may also have some software for diagnosing network

problems that is installed on the server or another computer.

If none of the above steps solve the problem, the next step is for the telecentre manager to contact the

ISP and ask for assistance. The customer support desk at an ISP should be able to diagnose some prob-

lems and help troubleshoot others. The tip box here includes some suggestions for a telecentre manager

to use when calling an ISP for support.


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Quick Summary

This Unit was mostly focusing on practical aspects of computer networking. The more you learn by doing

would increase your comfort level in computer networking. Some of the points discussed int this Unit are:

1. For the purpose of this Unit, setting-up a simple Local Area Network is discussed

2. Different networking equipments are needed to set-up a network. These are Router, Switch, CAT-5 cable,

etc.

3. A network printer can be shared with the entire network or a computer printer can be shared with other

computers in the network

4. Troubleshooting of a network failure was also discussed

Assignments

Draw a map of the computer network at your telecentre. Show all computers, switches, routers, servers and

network printers. Show how they connect to each other and to the Internet.

Add a network or shared printer to a computer in a computer network.

Practice using the help les on a computer or online searches to address network problems.


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07_ References

2G. (2010). In Wikipedia, The Free Encyclopedia. Retrieved March 23, 2010, from http://en.wikipedia.org/w/index.php?title=2G&oldid=351283538

Bradley, T. (2010). Introduction to Firewalls. (2010) In About.com: Internet/Network Security . Retrieved

February 17, 2010. http://netsecurity.about.com/od/hackertools/a/aa072004.htm

Brewer, D. (2009). Picture Yourself Networking Your Home or Small Ofce. Boston: Course Technology.

Camara (2009). Networking Course. Unpublished. For more information contact [email protected]

Computer Network. (2010, February 2). In Wikipedia, The Free Encyclopedia. Retrieved February 3, 2010,

from http://en.wikipedia.org/w/index.php?title=Computer_network&oldid=341486930

Dionys, D. (2008). How to Make a Network Cable. Unpublished. Produced for the VVOB Program in Zambia

2008-2013. For more information about VVOB see www.vvob.be.

General Packet Radio Service. (2010, February 2). In Wikipedia, The Free Encyclopedia. Re-

trieved February 10, 2010, from http://en.wikipedia.org/w/index.php?title=General_Packet_Radio_Service&oldid=341574212

High-Speed Downlink Packet Access. (2010). In Wikipedia, The Free Encyclopedia. Retrieved

March 23, 2010, from http://en.wikipedia.org/w/index.php?title=High-Speed_Downlink_Packet_

Access&oldid=350191690

Mitchell, B. (2010). Computer and Wireless Networking Basics. Retrieved March 1, 2010, from About.com:

http://compnetworking.about.com/od/basicneworkingconcepts/u/computer_networking_basics.htm

Mitchell, B. (2010). Introduction to Client Server Networks. Retrieved March 1, 2010, from About.com: http://

compnetworking.about.com/od/basicnetworkingfaqs/a/client-server.htm

Mitchell, B. (2010). Wireless Standards. Retrieved March 1, 2010, from About.com: http://compnetworking.

about.com/cs/wireless80211/a/aa80211standard.htm

Network. (n.d.). Dictionary.com Unabridged. Retrieved February 02, 2010, from Dictionary.com website:http://dictionary.reference.com/browse/network

Network topology. (2010, February 8). In Wikipedia, The Free Encyclopedia. Retrieved February 9, 2010,

from http://en.wikipedia.org/w/index.php?title=Network_topology&oldid=342762416

Proxy server. (2010, February 16). In Wikipedia, The Free Encyclopedia. Retrieved February 16, 2010, from

http://en.wikipedia.org/w/index.php?title=Proxy_server&oldid=344406104

Router. (2010, February 8). In Wikipedia, The Free Encyclopedia. Retrieved February 10, 2010, from http://

en.wikipedia.org/w/index.php?title=Router&oldid=342691135

WiDocs: Wireless Trouble Shooting Guide. (2009, November 25). In Ubuntu Documentation. Retrieved

February 16, 2010 from https://help.ubuntu.com/community/WiDocs/WirelessTroubleShootingGuide

08_ AcknowledgementsSpecial thanks to author Heidi Neff and Zambia Pacic Trust.

This curriculum has been developed by authors associated with the Telecentre.org Foundation and the Inter-

national Telecommunications Union.

Documents

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