LAB 3
DKT 224
PPK KOMPUTER & PERHUBUNGAN
Universiti Malaysia Perlis
DKT224 DATA COMMUNICATION & NETWORK
LAB3
NETWORK SET-UP
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Lab 3: Network Set-up
Objectives
1. To learn basics of Local Area Network (LAN)
2. To learn procedure to make Unshielded Twisted-Pair (UTP) cable
3. To learn the configuration and setting-up Ethernet Network Interface Card (NIC)
4. To learn the configuration of IP addresses, gateway and subnet mask
5. To learn the procedure to test and verify network connectivity using ping, ssh and ftp.
Background
What Is a LAN?
A LAN is a high-speed data network that covers a relatively small geographic area. It
typically connects workstations, personal computers, printers, servers, and other devices.
LANs offer computer users many advantages, including shared access to devices and
applications, file exchange between connected users, and communication between users
via electronic mail and other applications.
LAN Protocols and the OSI Reference Model
LAN protocols function at the lowest two layers of the OSI reference model i.e. between
the physical layer and the data link layer. Figure 1 illustrates how several popular LAN
protocols map to the OSI reference model.
Figure 1: Popular LAN Protocols Mapped to the OSI Reference Model
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Network Topologies
Some of the most common topologies in use today include:
Bus - Each node is daisy-chained (connected one right after the other) along the same
backbone, similar to Christmas lights. Information sent from a node travels along the
backbone until it reaches its destination node. Each end of a bus network must be
terminated with a resistor to keep the signal that is sent by a node across the network
from bouncing back when it reaches the end of the cable.
Figure 2: Bus network topology
Ring - Like a bus network, rings have the nodes daisy-chained. The difference is that
the end of the network comes back around to the first node, creating a complete circuit. In
a ring network, each node takes a turn sending and receiving information through the use
of a token. The token, along with any data, is sent from the first node to the second node,
which extracts the data addressed to it and adds any data it wishes to send. Then, the
second node passes the token and data to the third node, and so on until it comes back
around to the first node again. Only the node with the token is allowed to send data. All
other nodes must wait for the token to come to them.
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Figure 3: Ring network topology
Star - In a star network, each node is connected to a central device called a hub. The
hub takes a signal that comes from any node and passes it along to all the other nodes in
the network. A hub does not perform any type of filtering or routing of the data. It is
simply a junction that joins all the different nodes together.
Star bus - Probably the most common network topology in use today, star bus
combines elements of the star and bus topologies to create a versatile network
environment. Nodes in particular areas are connected to hubs (creating stars), and the
hubs are connected together along the network backbone (like a bus network). Quite
often, stars are nested within stars, as seen in the example in the next page.
Figure 4: Star network topology
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LAN Transmission Methods
LAN data transmissions fall into three classifications: unicast, multicast, and broadcast.
In each type of transmission, a single packet is sent to one or more nodes. In a unicast
transmission, a single packet is sent from the source to a destination on a network. First,
the source node addresses the packet by using the address of the destination node. The
package is then sent onto the network, and finally, the network passes the packet to its
destination. A multicast transmission consists of a single data packet that is copied and
sent to a specific subset of nodes on the network. First, the source node addresses the
packet by using a multicast address. The packet is then sent into the network, which
makes copies of the packet and sends a copy to each node that is part of the multicast
address.
A broadcast transmission consists of a single data packet that is copied and sent to all
nodes on the network. In these types of transmissions, the source node addresses the
packet by using the broadcast address. The packet is then sent on to the network, which
makes copies of the packet and sends a copy to every node on the network.
LAN Switch
Switches are data link layer devices that, like bridges, enable multiple physical LAN
segments to be interconnected into a single larger network. Similar to bridges, switches
forward and flood traffic based on MAC addresses. Any network device will create some
latency. Switches can use different forwarding techniques—two of these are store-andforward switching and cut-through switching. In store-and-forward switching, an entire
frame must be received before it is forwarded. This means that the latency through the
switch is relative to the frame size—the larger the frame size, the longer the delay
through the switch.
Cut-through switching allows the switch to begin forwarding the frame when enough of
the frame is received to make a forwarding decision. This reduces the latency through the
switch. Store-and-forward switching gives the switch
the opportunity to evaluate the frame for errors before forwarding it. This capability to
not forward frames containing errors is one of the advantages of switches over hubs. Cutthrough switching does not offer this advantage, so the switch might forward frames
containing errors. Many types of switches exist, including ATM switches, LAN switches,
and various types of WAN switches.
LAN switches are used to interconnect multiple LAN segments. LAN switching provides
dedicated, collision-free communication between network devices, with support for
multiple simultaneous conversations. LAN switches are designed to switch data frames at
high speeds.
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Ethernet Basics
Ethernet is a local area technology, with networks traditionally operating within a single
building, connecting devices in close proximity. At most, Ethernet devices could have
only a few hundred meters of cable between them, making it impractical to connect
geographically dispersed locations. Modern advancements have increased these distances
considerably, allowing Ethernet networks to span tens of kilometers.
Ethernet Terminology
Ethernet follows a simple set of rules that govern its basic operation. To better understand
these rules, it is important to understand the basics of Ethernet terminology.
Medium - Ethernet devices attach to a common medium that provides a path
along which the electronic signals will travel. Historically, this medium has been
coaxial copper cable, but today it is more commonly a twisted pair or fiber optic
cabling.
Segment - We refer to a single shared medium as an Ethernet segment.
Node - Devices that attach to that segment are stations or nodes.
Frame - The nodes communicate in short messages called frames, which are
variably sized chunks of information.
The Ethernet protocol specifies a set of rules for constructing frames. There are explicit
minimum and maximum lengths for frames, and a set of required pieces of information
that must appear in the frame. Each frame must include, for example, both a destination
address and a source address, which identify the recipient and the sender of the message.
The address uniquely identifies the node, just as a name identifies a particular person. No
two Ethernet devices should ever have the same address.
Ethernet Medium
Since a signal on the Ethernet medium reaches every attached node, the destination
address is critical to identify the intended recipient of the frame.
Figure 5: A small ethernet network
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For example, in the figure above, when computer B transmits to printer C, computers
A and D will still receive and examine the frame. However, when a station first receives a
frame, it checks the destination address to see if the frame is intended for itself. If it is
not, the station discards the frame without even examining its contents.
CSMA/CD
The acronym CSMA/CD signifies carrier-sense multiple access with collision detection
and describes how the Ethernet protocol regulates communication among nodes. Ethernet
uses a process called CSMA/CD to communicate across the network.
Under CSMA/CD, a node will not send out a packet unless the network is clear of traffic.
If two nodes send out packets at the same time, a collision occurs and the packets are lost.
Then both nodes wait a random amount of time and retransmit the packets. Any part of
the network where there is a possibility that packets from two or more nodes will
interfere with each other is considered to be part of the same collision domain. A network
with a large number of nodes on the same segment will often have a lot of collisions and
therefore a large collision domain.
UTP Cable
EIA/TIA wiring standards were first published in 1991 and has been evolving ever since.
The EIA/TIA-568 standard defines the specification of the cable to be used as well as
some installation rules. The latest version of the EIA/TIA standard is 568B, which
contains some minor enhancements to the original 1991 standard. The most popular is
Category 5, the highest-quality UTP cable. It is tested at 100 MHz, allowing it to run
high-speed protocols such as 100 Mbps Fast Ethernet and FDDI. Category 5 cable also
uses either 22 or 24 AWG unshielded twisted pair wires with impedance of 100 ohms.
The IEEE demands rigid compliance of how the cable is installed with RJ-45 connector.
Otherwise, you will have high-speed data transmission problem - NEXT. NEXT is the
coupling of signals from one twisted pair to another. NEXT is undesired because it
represents unwanted spillover from one pair to other. The result is corrupted data or no
connection at all.
Even you are using Cat 5 cable with 4 twisted pair wires, it doesn't mean that the cable is
100% compliant with EIA/TIA standard if it is not connected to RJ- 45 in the way it
should be. The Straight-through cable ("Patch cable") connection should be like
shown in figure 6:
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Figure 6: Straight through cable connection
Here is the pin-out for Crossover cable ("Uplink cable"):
Figure 7: Crossover cable
There is also another wiring standard - EIA/TIA-568A. Technically, there is no different
between 568A and 568B in Ethernet applications. However, if Ethernet system combined
with phone system is being used, most of the people will prefer 568A standard due to the
fact that 568B may have backward compatibility problem with standard Universal
Service Order Codes (USOC) hardware, which are commonly used in the telephone
infrastructure.
Figure 8: 568A and 568B Pin-out
Straight through cables - make both ends exactly the same, use only one of the two
color codes above for both ends of the cable.
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Crossover cables - make both ends different, one end with 568A and the other with
586B. Crossover cables have different ends, since they have the send and receive pairs
switched.
In the most general sense, crossover cables are used to connect like equipment, such as
two computers, or two hubs directly to each other. Straight through cables, on the
other hand are used to connect a computer to a hub, router or a cable modem. An
uplink port on a network device, such as switch or a router acts as a crossover. In other
words, a straight through cable connected to an uplink port is the same as a crossover
cable connected to a regular port.
To further confuse consumers, some modern hubs/switches can automatically detect and
switch ports to accommodate either crossover or straight-through cables. Although there
are 8 wires in an UTP cable, Ethernet only uses 4 of them (one pair for sending and one
pair for receiving information), the other 4 wires are actually wasted (or can be used for
another run, or other wiring wonders)
Practical work
Component and equipment:Item
1) Modular Plug Crimp Tool
2) UTP Category 5 Cable (6 feet)
3) RJ 45 Connector
4) Cable Tester & Battery
5) Switch (5 Ports)
6) Cutter
7) PC
Qty
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Project Details
In this lab session, students are required to set-up a Local Area Network
(LAN) consists of 3 PC’s by following the procedures as in 5. This project
must be done in group.
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Task
1. Ethernet Unshielded Twisted Pair (UTP) Cable Preparations
2 types of UTP cables:
• Straight-Through cables – T-586A standard (2 units)
– T-586B standard (2 units)
• Crossed cables – (1 unit)
References: Appendix A- Patch Cable Assembly Instructions
2. Configuration and Setting-up Ethernet Network Interface Card (NIC)
Reference: Appendix B- Network Configuration
3. Configuration of IP addresses, gateway and subnet mask.
Reference: Appendix B- Network Configuration
4. Connecting and testing connection between 2 PC’s using Crossed cable.
Connecting PC’s with switches.
5. Testing and verify network connectivity using ‘ping’ command.
6. Configure 1 PC as Server and the other PC’s as Client
Reference: Appendix C- Services Configuration Tools
7. Configuration and testing of server PC to activate ssh and ftp.
Reference: Appendix C- Services Configuration Tools
8. Configure Server PC to add new users (2 users)
9. Testing and verify connection using ssh and ftp command.
Upon the completion of your project,
i. Each group must present your LAN to the lab instructor.
ii. Lab Discussion:Write down a simple and brief discussion of what you have learnt from this
lab session.
Complete all the tasks in the given project.
Submit your report to your INSTRUCTOR. Do not copy other students work.
Make your own report.
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APPENDIX A: Patch Cable Assembly Instructions
Patch Cable Assembly Instructions
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APPENDIX B: Network Configuration
To communicate with other computers, computers need a network connection. This is
accomplished by having the operating system recognize an interface card (such as
Ethernet, ISDN modem, or token ring) and configuring the interface to connect to the
network.
To use the Network Administration Tool, you must have root privileges. To start the
application, go to the Main Menu Button (on the Panel) => System Settings =>
Network, or type the command redhat-config-network at a shell prompt. If you type the
command, the graphical version is displayed if X is running; otherwise, the text-based
version is displayed. To force the text-based version to run, use the redhat-confignetwork-tui command.
Figure 9: Network Administration Tool
To configure a network connection with the Network Administration Tool, perform the
following steps:
1. Add the physical hardware device to the hardware list.
2. Add a network device associated with the physical hardware device.
3. Configure the hostname and DNS settings.
4. Configure any hosts that cannot be looked up through DNS.
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Establishing an Ethernet Connection
To establish an Ethernet connection, you need a network interface card (NIC), a network
cable (usually a CAT5 cable), and a network to connect to. Different networks are
configured to use different network speeds; make sure your NIC is compatible with the
network to which you want to connect.
To add an Ethernet connection, follow these steps:
1. Click the Devices tab.
2. Click the New button on the toolbar.
3. Select Ethernet connection from the Device Type list, and click Forward.
4. If you have already added the network interface card to the hardware list, select it from
the Ethernet card list. Otherwise, select Other Ethernet Card to add the hardware
device.
5. If you selected Other Ethernet Card, the Select Ethernet Adapter window appears.
Select the manufacturer and model of the Ethernet card. Select the device name. If this is
the system's first Ethernet card, select eth0 as the device name; if this is the second
Ethernet card, select eth1 (and so on). The Network Administration Tool also allows
you to configure the resources for the NIC. Click Forward to continue.
6. In the Configure Network Settings window as shown in figure 10, choose between
DHCP and a static IP address.
7. Click Apply on the Create Ethernet Device page.
Figure 10: Ethernet Settings
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After configuring the Ethernet device, it appears in the device list as shown in Figure 11.
Figure 11: Ethernet Device
Be sure to select File => Save to save the changes.
After adding the Ethernet device, you can edit its configuration by selecting the device
from the device list and clicking Edit. For example, when the device is added, it is
configured to start at boot time by default. To change this setting, select to edit the
device, modify the Activate device when computer starts value, and save the changes.
When the device is added, it is not activated immediately, as seen by its Inactive status.
To activate the device, select it from the device list, and click the Activate button. This
step does not have to be performed again, if the system is configured to activate the
device when the computer starts (the default). If you associate more than one device with
an Ethernet card, the subsequent devices are device aliases. A device alias allows you to
setup multiple virtual devices for one physical device, thus giving the one physical device
more than one IP address. For example, you can configure an eth1 device and an eth1:1
device.
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APPENDIX C: Services Configuration Tools
Services Configuration Tool is a graphical application developed by Red Hat to
configure which SysV services in /etc/rc.d/init.d are started at boot time (for runlevels 3,
4, and 5) and which xinetd services are enabled. It also allows you to start, stop, and
restart SysV services as well as restart xinetd.
To start Services Configuration Tool from the desktop, go to the Main Menu Button
(on the Panel) => Server Settings => Services or type the command redhat-configservices at a shell prompt.
Figure 12: Service configuration
Services Configuration Tool displays the current runlevel as well as which runlevel you
are currently editing.
Services Configuration Tool lists the services from /etc/rc.d/init.d as well as the services
controlled by xinetd. Click on a service to display a brief description of that service at the
bottom of the window.
To start, stop, or restart a service immediately, select the service and choose the action
from the Actions pulldown menu. You can also select the service and click the start, stop,
or restart button on the toolbar.
If you select an xinetd service such as telnet, the Start, Stop, and Restart buttons will
not be active. If you change the Start at Boot value of an xinetd service, you must click
the Save Changes button to restart xinetd and disable/enable the xinetd services that you
changed.
To enable a service at boot time for the currently selected runlevel, check the checkbox
beside the name of the service under the Start at Boot column. After configuring the
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runlevel, you must apply the changes. Select File => Save Changes from the pull down
menu or click the Save Changes button.
To test the ssh function you need to create your own account on the server PC. After you
have created your own account try to login to the server PC from any computer that
attached on the same network with the server. At the command prompt type:
ssh [email protected]
(xxx.xxx.xxx.xxx is the IP address of the server)
Then the system will request for password that you had set earlier when you created the
account.
Warning
When you save changes to xinetd services, xinetd is restarted. When you save changes to
other services, the runlevel is reconfigured, but the changes do not take effect
immediately.
Summary
1) From GNOME Menu, select Server Settings then Services, followed by Service
Configuration.
2) To activate the ssh and ftp you must check all 3 services as listed below.
a.
sshd ------- Open SSH Server daemon
b.
vsftpd --------The vsftpd FTP server serves FTP connections. It uses
normal, unencrypted usernames and passwords for authentication. You
must enable xinetd to use this service.
c.
xinetd --------xinetd is a powerful replacement for inetd. xinetd has access
control mechanisms, extensive logging capabilities, the ability to make
services available based on time, and can place limits on the number of
servers that can be started, among other things
3) Restart
4) Restart PC.
Reference:
i. www.redhat.com
ii. www.linuxsupport.com
iii. www.makeitsimple.com
iv. www.computer.howstuffworks.com
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