Prof. Michael P. Harris, CCNA CCAI
ITNW 1454 – Implementing & Supporting Servers
Chapter 5
Networking Components
Implementing & Supporting Servers – Chapter 5
Networking Components
Chapter Overview
In this chapter, we discussed the selection and use of networking hardware. Here are some
of the key points.
Learning Objectives
Objective 1.6: Identify the purpose, features, and functions of the following network
components
Objective 3.3: Identify the main characteristics of VLANs
Lecture Notes
Hubs
Hubs are the most basic form of multistation access unit. They are used to connect devices,
such as computers and printers, in a network. They may be used to connect different
network segments together.
Passive Hubs
A passive hub takes the signal (data) that it receives from a device, copies it, and sends it
out the other ports in the hub to all the other networked devices. It does not manipulate or
view the data and it does nothing to amplify, clean up, or change the data signal. Passive
hubs extend only the length of the cable that is being used on the network.
Active Hubs
Active hubs have the ability to repair weak signals. They do this by regenerating or
amplifying the data signal. This regeneration consists of intercepting a week signal and
raising it back up to the original voltage. Once the signal is regenerated, it is sent back out
of the hub to all the other devices. An active hub can be used to add computers to a network
or to allow for increased distances between workstations and servers. It is also called a
repeater.
Managed, or Intelligent, Hubs
A managed, or intelligent, hub allows you to configure and monitor each individual port.
Ports can be enabled or disabled through a hub management utility that is normally provided
by the manufacturer. Hub management will also allow you to gather network parameters
such as the number of errors that have occurred, and the number of collisions taking place on
the network.
Jerry K. Ainsworth, Kristine A. Kriegel, SYSTEM ADMINISTRATION
EMCParadigm ©2004
Page 1 of 6
ISBN: 0-7638-1972-7
Prof. Michael P. Harris, CCNA CCAI
ITNW 1454 – Implementing & Supporting Servers
Chapter 5
Networking Components
Switches
Instead of just copying and sending data out to every device on the network, a switch has the
ability to learn the physical addresses of all of the devices on the network. Reducing network
Traffic also helps cut down on the number of data collisions that take place on the Ethernet
networks. Most switches have the ability to auto-sense network transmission speeds. Layer 3
switches incorporate features of both routers and switches.
Virtual Local Area Network (VLAN)
A VLAN is a group of network devices (workstations, servers, printers, ect.) that can be
grouped into a logical network, without regard for physical location. All of the devices act as
though they are connected to a single network segment, even though they may be physically
located in different buildings or even different states. The three basic VLAN models are
identified by how the VLAN is established:
1) Port-based: a network administrator assigns each port a switch to a VLAN.
2) MAC address-based: Membership on the VLAN is based on source and destination MAC
addresses of the devices that are attached to the switch.
3) Protocol-based: Protocol-based VLANs, also known as layer 3VLANs, are based on the
protocols being used (IP, IPX, ect.) and their respective Layer 3 (OSI Model Network
layer) addresses.
Bridges
The primary purpose of a bridge is to allow devices that are attached to separate LANs or LAN
segments to communicate as if they were all located on the same one. They are also able to
contain network traffic to the section of the network to which it belongs. It can also be
configured to deny or reject traffic on one segment from being transmitted to another
segment. Bridges decide which packets to pass between networks through the use of a
routing table. Bridges are typically classified as either local or remote.
 Local bridges exist when there is a direct connection between several LAN segments.
 Remote bridges use WAN connections, generally leased telephone lines, to connect
LAN segments.
The four basic types of bridging algorithms are transparent, source-route, translational, and
source-route transparent.
Transparent
The transparent bridge has the capability of automatically identifying all of the devices that
are connected to each segment of the network. It listens to traffic traveling on the network
and learns the addresses of devices that are located on the segments and stores the
information on a table within the bridge. Whenever the bridge receives a packet, it can
check its internal table to determine exactly where the destination device is located.
Source-Route
Source-route bridging is commonly found on Token Ring networks. To communicate on a
source-route network, a device first sends a broadcast across the network. When the
destination device hears the broadcast packet took to get to the destination device.
Jerry K. Ainsworth, Kristine A. Kriegel, SYSTEM ADMINISTRATION
EMCParadigm ©2004
Page 2 of 6
ISBN: 0-7638-1972-7
Prof. Michael P. Harris, CCNA CCAI
ITNW 1454 – Implementing & Supporting Servers
Chapter 5
Networking Components
Translational
Translational bridges are used to connect dissimilar networks together. For example, a
bridge could be used to connect to Ethernet network segment to a Token Ring network
segment. The conversion of the frames from one type to another is typically done through
encapsulation.
Source-Route Transparent
Source-route transparent bridges combine aspects of both source-route and translational
bridges in order to enable communication on networks with a mix of Ethernet and Token Ring
technologies.
Routers
A router is a device that connects multiple network segments together to form a larger
network, or large networks together to form an internetwork. Each CSU communicates with
another CSU that is located at the other end of the data line. The CSU has the ability to
monitor the data line and provides some error correction for the data line. A DSU provides a
terminal connection to a digital line. It operates essentially as a digital modem, converting
the digital data frame that is used on the LAN into a frame that con be transmitted over a
WAN and vice versa.
Network Interface Cards
The network interface card (NIC) is the piece of hardware installed inside a computer that
allows the computer to be connected to the network. It is plugged into an expansion slot on
the computer’s motherboard. Once physically installed, a network cable can be plugged into
a port on the back of the NIC. A piece of software known as a driver is then installed to allow
the computer’s operating system to interact with the NIC. The NIC and the driver work
together to support the Data Link layer protocol (Ethernet or Token Ring), the network access
method (CSMA/CD) or token passing), and other features.
Integrated Services Digital Network (ISDN) Adapters
Integrated Services Digital Network (ISDN) is a communications technology that allows
digital signals to pass through normal telephone lines, also referred to as plain old telephone
service (POTS) or public switched telephone networks (PSTN). ISDN allows you to combine
one or more communications channels to provide high data transfer speeds, generally in the
area of 128Kbps. A terminal adapter is used as the interface between the IADN line and your
computer. The adapter will support one of two interfaces, U interface or S/T interface:
 The U interface is used when transmitting the data signal over long distances, such as
from your home to a telephone switching station or the central telephone office.
 The S/T interface is used when transmitting data signal over short distances, such as
from a wall jack to your ISDN adapter.
 If your adapter has an S/T interface, you will need to purchase a network termination,
commonly referred to as an NT-1.
Jerry K. Ainsworth, Kristine A. Kriegel, SYSTEM ADMINISTRATION
EMCParadigm ©2004
Page 3 of 6
ISBN: 0-7638-1972-7
Prof. Michael P. Harris, CCNA CCAI
ITNW 1454 – Implementing & Supporting Servers
Chapter 5
Networking Components
Wireless Access Points (APs)
A wireless access point (AP) is the place a wireless network interface card communicates
with to connect to the network. A wireless network card acts like a hub on a wired network.
An access point can support a small group of users and generally has a range up to several
hundred feet.
Modems
A modem is a piece of hardware that transforms data from inside the computer into a
form that can be transmitted over some type of cable media. When using a modem for
data communication, the modem “modulates” which means it takes the digital signal
from your computer and changes it into analog signal that can be transmitted over the
cable media. When it receives data, the modem “demodulates,” meaning it takes the
analog signal from the cable and changes it into a digital signal that can be understood by
the computer. There are three basic categories of modems: traditional, Digital
Subscriber Line (DSL), and cable.
 Traditional: The traditional modem allows a computer to connect to a network using
a dial-up telephone line.
 Digital Subscriber Line (DSL): Modems also support data transfer over POTS or PSTN
networks; however, DSL uses higher frequencies than traditional modems.
 Cable: Cable modem service is another high-speed networking technology that uses
the same coaxial cable that powers cable television in most homes.
Troubleshooting Network Devices
 Check the lights over each port to see if they are glowing or flashing, depending on
the lighting configuration on the device.
 If the light on the port where the device is plugged in is not glowing or flashing, there
is a connectivity problem.
 Plug the cable into another port and see if that light comes on. If it does, a bad port
on the device is indicated.
 If the light does not come on, check the cable.
 If all the port lights are glowing instead of flashing, recycle the power on the device.
 If you are using a switch in a VLAN configuration, recheck the configuration of the
ports on the switch.
 Always check for recent configuration changes that may affect the performance of the
device, especially with managed hubs and switches.
Troubleshooting Bridges and Routers
Many of the same procedures outlined for hubs and switches apply to bridges as well.
Troubleshooting Gateways
Gateways present unique problems because they are a combination of hardware and
software. Troubleshooting gateway problems involves working at all layers, requiring a
through understanding of each component involved. The first step in the process is to
determine where in the chain the problem lies. Use standard troubleshooting tools such as
Jerry K. Ainsworth, Kristine A. Kriegel, SYSTEM ADMINISTRATION
EMCParadigm ©2004
Page 4 of 6
ISBN: 0-7638-1972-7
Prof. Michael P. Harris, CCNA CCAI
ITNW 1454 – Implementing & Supporting Servers
Chapter 5
Networking Components
error messages or event logs to narrow down where the problem is. Work on one concern at a
time. For example, if you suspect a hardware problem, do not start substituting new
hardware while someone else makes software configuration changes. If you determine that
the problem is hardware related, repair or replace the hardware. This includes the
associated cables. If the problem is software related, follow the manufacturer’s
recommendations for repairing the problem.
Troubleshooting Network Interface Cards and Other Adapters
 Check the Device Manager utility to ensure the adapter is installed and functioning
correctly.
 Check all cable connections to make sure they are secure and plugged into the correct
ports.
 Is the data line functioning? Try to make a phone call or turn on your cable television
to see if you have a signal.
 Use some of the TCP/IP utilities to check for problem areas, such as the default
gateway and DNS servers.
Troubleshooting Wireless Access Points
 Check the signal strength in the area around the access point.
 Check the wireless network device to see if it can associate with another access point.
 Check the configuration of the access point to see if only certain devices are allowed
to connect to it.
 Check the channel settings of both the access point and the wireless device.
Jerry K. Ainsworth, Kristine A. Kriegel, SYSTEM ADMINISTRATION
EMCParadigm ©2004
Page 5 of 6
ISBN: 0-7638-1972-7
Prof. Michael P. Harris, CCNA CCAI
ITNW 1454 – Implementing & Supporting Servers
Jerry K. Ainsworth, Kristine A. Kriegel, SYSTEM ADMINISTRATION
EMCParadigm ©2004
Chapter 5
Networking Components
Page 6 of 6
ISBN: 0-7638-1972-7