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This is a Clilstore unit. You can link all words to dictionaries.



4t E.S.O




1.1 LANS. Local Area Network

1.2 Wide Area Lans (WAN)

1.3 Metropolitan Area Networks

1.4 Home Area Network (HAN)


















1.1 Local Area Networks

The most spread networks in organizations are LAN (Local area networks). A Local Area Network is limited to a small area, usually a building or a campus of maximum 200m.


Nowadays, most L.A.N.'s are Ethernet networks. These networks are characterized by using twisted pair and fiber optic cable as transmission media. Networks using Ethernet divide a stream of data into shorter pieces called frames. Each frame contains source and destination addresses and error-checking data so that damaged frames can be detected, discarded and re-transmitted. The Ethernet standards encompass several wiring and signaling variants. The original Ethernet used a coaxial cable similar to those of TV as a shared medium. Later the coaxial cables were replaced with twisted pair and fiber optic links in conjunction with hubs or switches.


Nowadays there are several forms of Ethernet networks. The most widespread are Fastethenet which allows a speed of 100Mb / s. Also Gigabit Ethernet networks are becoming common (up to 1000Mb/s)



Some L.A.N. examples:






1.2 Wide Area Networks


A wide area network is a set of local area networks that extend covering a large geographical area and which are interconnected by an infrastructure of high speed links. Usually they use optical fiber or Serial high performance wired connections in the backbone, allowing data transfers between the different LAN's



1.3 Metropolitan area network (MAN)

A metropolitan area network (MAN) is a network that interconnects users with computer resources in a geographic area or region larger than that covered by local area network (LAN) but smaller than the one covered by a wide area network (WAN).

1.4 Home Area Network (HAN)

A home network or home area network (HAN) is a type of local area network with the purpose to facilitate communication among digital devices in a home. The importance of this networks are steadily rising, due to the spread of digital household devices able to connect to Internet.

ACTIVITY 1 : Consider the following examples of networks, and keeping in mind the type of organization, the predictable number of computers on them, and their size, classify them in LAN, WAN, MAN and HAN. Solve the question in the first question in the quizz Research and discussion in Moodle



Within a network the devices can be classified by function as:






End devices

Computers,Printers,Tablets,Fax, SMART TV'S, Game Consoles, mobile phone's


Devices used to connect devices inside the LAN



Used to connect devices from DIFFERENT LAN's


Later you will find out why this classification is so important in order to achieve a feasible network simulation.





A Network card is a device that connects a computer to a computer network, usually a LAN. The Network card is also called a network adapter or NIC (Network Interface Card). There are different types of adapters depending on the type of wire used, (fiber optic, twisted pair), or the architecture used in the network (Ethernet, Fast Ethernet, Gigabit Ethernet, serial interfaces), but currently the most common is the FastEthernet using an RJ-45 connector and twisted pair cable.

Fast Ethernet Network Interface


Serial Network Interface




The MAC address ("media access control") is an identifier of 48 bits (6 bytes, each represented by two hexadecimal digits) that identifies uniquely a network card. It is also known as physical address. MAC addresses are globally unique, since they are written directly, in binary form, in the network card by the manufacturer. There aren't two NICs in the world with the same MAC address

example of MAC address








3.1 Twisted pair cable

This cable is made up of a variable number of copper wire pairs that are entangled each other to reduce the electromagnetic noise (interference).


This type of cable is used massively in most local area networks. The Ethernet lan's uses a four twisted pair cable ended in an RJ45 connector like the one shown int the bottom figure.

In Shielded Twisted pair cables (STP) there is a sheet of foil covering the twisted wire pairs to enhance their protection from external interference. This allows increased performance at the cost of a higher price. For this reason this cables are only used in special purposes. The Unshielded variant (known as UTP cable) is the conventional cable found in a typical LAN.





Twisted pair cable

RJ45 plug

Shielded Twisted Pair cable (STP)


Twisted pair cable can also be classified in categories (CAT-1, CAT-2.. and so on) by its quality level. The most widespread cable in today's networks are STP and UTP Category 5 (CAT 5) cable for both Fastethernet (100mb/s) and Gigabit networks (1000mb/s). Category 6 and 7 ( CAT 6 and CAT 7) cables are improved versions of higher quality and price use for special purposes.


There are two types of twisted pair connections. The difference is very important in order to carry out correctly the activities that we will perform in the following sessions:


The twisted pair:

Allows high transmission rates (up to 1 gigabit / s, ie 1024mb / s)
  1. it is cheap

  2. It can only be used over short distances (always less than 100m). This limits their use to Local Area Networks


ACTIVITY 3 In this activity we will connect two Pcs using a twisted pair cable









ACTIVITY 4. What's the cause of the problem set forth in the previous paragraph. Consider the following hypothesis and discuss about them. You must come up with a list of points supporting or discarding them. If you can not figure out the right answer, go ahead with the next activity, and come back to solve this later.
a) It's impossible to connect two computers by cable. It's necessary a wireless connection
b) We are using direct cable. we should use a crossover cable due to the devices level
c) We are using crossover cable. We should use a straight cable due to the devices level.
d) We should use a optical fiber cable due to the red dots







Now, we will explore the network card of the PC's in order to find out their physical address (MAC address)



Save the file and upload it to moodle, using the link UPLOAD ACTIVITY 5

3.3 Optical fiber


With optical fiber cable connectors

Optical fiber cable



ACTIVITY 6. Connecting two PCS through an optical fiber cable.

In this activity we will do the same we did in the previous session, but connecting the PCs with another type of cable: optical fiber. The computers now have a FastEthernet network card, which means they use twisted pair cable. So the first thing we have to do is to replace the network card by an optical fiber card.


Drag the card out of the PC by clicking on it and dragging the rectangle in the lower right corner out of the window






Save your activity and upload it to Moodle using the link UPLOAD ACTIVITY 6



Two PC's connected by a cable are not a computer network. What if we want to connect 10 computers instead of just 2? Do we need to install 10 Network cards in any PC in order to get them interconnected?? Obviously, that's not a good solution.

To connect multiple computers to the same network we must use a type of device called a SWITCH. A switch is a device with several integrated Ethernet ports, that allows the connection of multiple devices. The switch provides other services as signal regeneration, some security issues and specially, it offers tools for centralized management of the network.

Activity 7. Setting up a 4 computers network




Save the file and upload it to Moodle




A ring network is a network in which all computers are connected together forming a ring


The main drawback of ring networks is that in order to close the ring, each computer must be connected to two partners, and needs two network cards. In Packet Tracer a generic PC only can have a network card. For this reasons we will use a device called Generic Server

In the following picture, you can see the Generic Server highlighted with a yellow circle. If you click on the server, the configuration window will open. Select the physical tab. There is a free slot for a second network card (marked in the picture with a red circle).

Upload the Packet Tracer File to Moodle using the link Upload activity 8


Building a computer network is not as simple as to wire several computers. When a data packet is transmitted, it must be clear for all the participants who is the sender, and who must be the receiver. In the telephone network this problem is solved by the use of telephone numbers: when a call is made ​​the receiver's phone number must be dialed. In computers the solutions follow a similar but more complex pattern called routing.

We still know an addressing mechanism in networks: the physical addressing or Mac address used by the network cards. However this type of addressing, is not suitable for large networks by different reasons. One of the most important is that, the Mac address must be complex in order to allow one different address for any card in the world. But for a common user it's too difficult to dial a hexadecimal number of 8 digits as 0030A3AA570C


Internally, computers directly wired use physical addressing to communicate among them. However, both for small networks as for huge ones as the Internet,the addressing mechanism used is called IP address (IP stands for Internet Protocol). In a nutshell, this is how it works:


The IP address is made up of 4 digits ranging from 0 to 254 and separated by a dot. Examples of proper IP addresses would be:

E Examples of incorrect IP addresses would be:

258 .33.2.3- There's a digit over 255

0 .3.2.3 - The first digit can not be 0

255.255 .243.12- number 255 is reserved .22- are five digits instead of 4

ACTIVITY 9. Answer in Moodle the Research and discuss switch the question labeled as activity 9.


The IP address is divided in two parts



In the image above there are two networks. The network on the left has a network address. All computers in each of the networks share the same network address and differ by having a different host number. Therefore in the left network the computers are identified by the following IP addresses

192.168.18 . 99

192.168.18 .11

192.168.18 .22

192.168.18 .33


The network identifier of the image right network is The host numbers are 11,22 and 33:



A mask is used in order to distinguish which part of the IP address is the network address and the host address. The mask is a 4 digits among 0 and 255 and separated by points. Though in real networks there are many different masks, in this unit we will consider only three possible masks



The first digit is the network address, the rest are station addresses

The first and second digits are the network address, the rest are station addresses

The first, second and third digits are the network address, the rest are station addresses


IP Address


Network address

Host address







Pay attention to the following statement because it is very important.


In an IP network, two computers can only communicate with each other, if they have the same network address.

Obviously, they also must be connected by a cable. But even though correctely physically connected, the computers only will be able to communicate each other if  both have the same network address


ACTIVITY 10. Solve in Moodle the activity 10, IP ADDRESS DRILLING



Activity 11 Designing Ip addresses for a 8 hosts network.



Now all PCs seem to be connected. However they still can not send or receive anything because they have no IP addresses either no network masks


Just fill in the IP Configuration section with the following data





Configure the other computers with the following IP addresses and masks, following the explained procedure


IP Address










Notice that what we have done is to set up two different networks.




Remember the rule: although they are connected, only those computers who have the same network address can exchange data packets. We are going to check out whether this rule is true




As you can see when PC1 pings to a computer that is located in a different network address, there is no answer. All the frames are lost.

Save the file and upload it to Moodle


So far, we have learned that it is not possible to connect two computers that are not configured with an IP address belonging to the same network address. However this does not match at all with our everyday experience. When we connect to the internet, we are able to connect with millions of computers each of which is in a completely different network address. This is possible thanks to another kind of devices: the routers.

A router is a device that allows connection between networks with different network addresses. An example

In the network shown in the image there are two computer networks, both with the mask PCs from the top left network belong to the network address, and the bottom right computers are on the address network. Therefore they are not able to communicate each other.


The router is the round sampled device in the middle of the network. Notice it is linked with both networks. A router is a third level device, which two or more network interfaces in order to be connected to two or more networks. The function of the router is to allow communication between the computers on different networks


When H8 wants to send a data packet to H3 wich is a computer out of its own network, it sends it to the Router. The router looks into the destination address, and 'routes' the packet to the correct output (that is, it sends the packet for the network interface connected to the network where H3 is located)


Therefore the computers in a network, in order to be able to communicate with other networks, must be configured with the IP address and network mask of the router interface connected to them. This interface is called a GATEWAY.

ACTIVITY 12. Using CISCO Packet Tracer design the network shown in the figure above.


We must test if it is working. If all goes right, we will be able to ping from H3 to H8 and receive a "pong".


Save the activity as activity 6 and upload it to Moodle





So far, we are setting the IP addresses manually in every computer. In a network with many computers scattered throughout a large geographical area this brings about lots of work and serious problems. For instance: two different computers might get accidentally the same IP address, that's a serious problem. Or someone will have to change the IP address anytime a computer is changed of LAN. Thats a lot of work. There is a protocol called DHCP that provides a better solution. In DHCP, whenever a network computer boots up, it looks for a DHCP server on the network, and ask it an IP configuration. DHCP servers assigns correct IP addresses avoiding repeated configurations in the network











Let's try if our DHCP server is working.


Upload to Moodle the Activity 14


8. Domain Name System (DNS)



Domain Name System or DNS is a system for naming computers connected to the Internet or a private network . For most people it's difficult to memorize numbers as an IP addresses. Instead humans are good at memorizing words, so it is much easier for a human to remember something like than its equivalent IP address. This is the reason why the DNS system was developed: to translate (resolve) names intelligible to humans to IP addresses with the purpose of locating and routing equipment worldwide on the Internet.


DNS names are based on a hierarchy. All Internet names must have a primary domain name as com, org, net, UN, es, fr, it etc. These names are useful classifying Internet servers by its main function. Commercial companies take the .com domain. The nonprofit organizations often use .org. Another possibility is to identify the country where their server is located. In the case of Spanish organization and companies the primary domain is .es


Left to the primary domain, and separated by a dot, comes the domain name of the organization. This is the word used to identify that company on the Internet. Examples are,,,


Some organizations add a subdomain. For example the Valencian Goverment uses the domain But the Education Department, uses the domain


The last component of a DNS name is the name of the server within the domain. For example, the Antares computer, in the Education Department would use the following dns name:


By the way, when accessing any website with a name that begins with www, for instance: , we are connecting to a computer named www, which belongs to the specified domain, in this case . Organizations always puts his web servers the name www, to make predictable for user the name of their web site.

DNS servers

On Internet someone has to do the translation (resolution) of a name into an IP address and vice versa. The Internet consists of billions of computers, so it is impossible to put all them in a unique data base shared by all DNS servers. This Database would be too huge and it would be impossible to deal with all the constant updates. DNS is based on a distributed database in which there are multiple DNS servers each responsible for its own section of Internet and depending on a higher authority over them. For this reason has been established the following hierarchy of DNS servers


When a user puts in your browser the URL the resolution of this name goes as follows:




Finally the local DNS server answers the question asked for your browser, handing him in the IP address of

ACTIVITY 11. Your group must search on Internet information about the root servers on Internet, and then answer the following questions:

Upload your answers to moodle






  • PC0


  • PC1


  • PC2


  • PC3
























When the IP protocol was developed, it was thought that 32 bits (four numbers from 0 to254) would be enough to assign an IP address to every computer in the world, because there were 4.294.967.296 of them.


This number of IP addresses can seem enormous. But actually the world has nearly run out of them.




There are several solutions to this problem: the main solution is the IPV6 protocol. IPv6 addresses are made of 128 bits (32 hexadecimal digits), which results in 2138 IPv6 addresses. This means a staggering 6.7 trillion IPV6 addresses per square millimeter on the planet. It is foreseeable that there wont be any scarcity of IPv6 address over a long period of time.


But until IPv6 is fully introduced, the only way to save IP addresses is the world is the private and public system of IP's directions.




Using this trick we save many millions of public IP addresses. Before this system, an organization with 1000 computers needed 1000 public IP's. Now it only might need one Ip public address for its router. The other 999 computers would use private IP and when they would need to access the Internet, they will ask its router to do it for them. Private IP addresses can be reused again and again in computers belonging to differents LANs reducing drastically the number of public IP's the world needs.


At home for example, even if you have multiple network enabled devices, only the router has a public IP address provided by your ISP. Other devices on your local network are private IP addresses assigned by your router.


The following table shows the private IP addresses ranges


ACTIVITY 17. public IP addresses.


In order to do this activity you need to log in our Moodle and download the file simulación_internet.pka. In this file a cloud of routers simulates how the Internet works.







ACTIVITY 18 local network for a school.

In this activity we are going to build a local network for a school where there will be two classrooms equipped with 10 computers.




Save the file and upload it to moodle.


ACTIVITY 19. Local network with DHCP server

In the previous activity we have built a small local network with static IP addresses, that is, the network administrator (you) had to set up each computer IP individually. However, in a Linksys wireless router, we can enable the DHCP service so that the router could assign IP addresses dynamically.

Open the file Simulación_internet.pka and save it as activity16.

Follow the next steps:








Wireless communication (WIFI)

WIFI is a mechanism for connecting electronic devices wireless. In a wireless communication the medium used is shared (the cable is the air!!!), and this has many negative implications. However the advantages make it afford to get over the problems: the stations can be mobile and no cable is needed. That is the reason why WIFI networks are thriving



Wi-Fi: is a trademark of the Wi-Fi Alliance, this organization tests and certificates that the equipment meets the standards related to wireless local area networks.

802.11 : The 802.11 standards establish a series of requirements that must meet the network devices to be considered compatible.

The standards IEEE 802.11b , IEEE 802.11g and IEEE 802.11n operates in the band of 2.4 GHz with a speed of up to 11 Mbit / s , 54 Mbit / s and 300 Mbit / s, respectively.



In this activity we are going to recreate a home network for a family of three, Juan, Maria, and his son Juanito







Router as Fast Ethernet and Wireless SWITCH




The router as DHCP server

This type of router is designed to provide a home user everything he could need to set up a home network. The router integrates a DHCP server to provide private IP addresses to each of the connected devices. Just connect the computers to the router by wify or cable and it will get a full Ip configuration.



Let's check connectivity by pinging between the PC of John, Mary, Iphone and Xbox.





Connecting the Linksys to the router 110.




But in our simulation the router 160 is not a DHCP server and the IP address of the router Ethernet interface have to be set up manually.




Save the file and upload it to Moodle.




Short url: