Network+ Guide to Networks
Third Edition
Chapter 5:
Networking Hardware
Objectives
Identify the functions of LAN connectivity
hardware
Install and configure a network adapter
(network interface card)
Identify problems associated with
connectivity hardware
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Objectives (continued)
Describe the factors involved in choosing
a network adapter, hub, switch, or router
Discuss the functions of repeaters, hubs,
bridges, switches, routers, and gateways,
and the OSI Model layers at which they
operate
Describe the uses and types of routing
protocols
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Network Adapters
• Also called network interface cards, NICs, or
network cards
• Connectivity devices that enable a workstation,
server, printer, or other node to receive and
transmit data over the network media
• NICs belong to both the Physical layer and Data
Link layer of the OSI Model, because they apply
data signals to the wire and assemble or
disassemble data frames
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Network Adapters (continued)
• Types of Network Adapters
• Expansion Board Network Adapters
• A circuit board used to connect a device to the
system board (the main circuit board that controls a
computer, also known as a motherboard)
• Expansion boards connect to the system board
through expansion slots, which are openings with
multiple electrical contacts into which the expansion
board can be inserted
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Network Adapters (continued)
• The circuit, or signaling pathway, used by the
system board to transmit data to the computer’s
components is the computer’s bus
• The capacity of a bus is defined principally by
the width of its data path (expressed in bits) and
its clock speed (expressed in MHz)
• A data path size equals the number of bits that it
can transmit in parallel at any given time
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Network Adapters (continued)
• PCI (Peripheral Component Interconnect) is a 32or 64-bit bus with a 33- or 66-MHz clock speed
whose maximum data transfer rate is 264 MBps
• The most popular expansion board NIC is one that
uses a PCI bus
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Network Adapters (continued)
• Characterized by a shorter connector length and a
much faster data transmission capability than
previous bus types (such as ISA or EISA)
• PCI adapters work within both PCs and Macintosh
computers, allowing an organization to standardize
on one type of NIC for use with all of its
workstations
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Network Adapters (continued)
• A newer version of the PCI standard is PCI
Express, which specifies a 64-bit bus with a 133MHz clock speed capable of transferring data at
up to 500 MBps in full-duplex transmission
• More efficient data transfer, support for quality of
service distinctions, error reporting and handling,
and compatibility with the current PCI software
• Designed to fit into PCs that currently have older
PCI slots
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Network Adapters (continued)
• Externally Attached Network Adapters
• USB (universal serial bus), PCMCIA (Personal
Computer Memory Card International Association),
or CompactFlash slots are used to connect network
adapters
• One advantage to externally attached network
adapters is their simple installation
• The first standard PCMCIA-standard adapter to be
released, called PC Card, specified a 16-bit
interface running at 8 MHz
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Network Adapters (continued)
• USB (universal serial bus) port is a standard
interface used to connect multiple type of
peripherals, including modems, mice, audio players,
and network adapters
• USB adapters may follow one of two USB
standards: USB 1.1 or USB 2.0
• The primary difference between the two
standards is speed
• The USB 1.1 standard has a maximum data
transfer rate of 12 Mbps and the 2.0 standard
can reach 480 Mbps
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Network Adapters (continued)
• Compact Flash as an ultra-small removable data
and input/output device that would connect to many
kinds of peripherals
• Compact Flash slots can also be used to connect to
a network
• Compact Flash network adapters are most likely to
be found connecting devices too small to handle
PCMCIA slots
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Network Adapters (continued)
• Wireless Network Adapters use an antenna (either
internal or external) to exchange signals with a
base station transceiver or another wireless NIC
• One disadvantage to using wireless network
adapters is that currently they are somewhat more
expensive than wire-bound network adapters
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Network Adapters (continued)
• Installing Network Adapters
• Firmware, a set of data or instructions that has
been saved to a read-only memory (ROM) chip
(which is on the network adapter)
• Data can be erased or changed by applying
electrical charges to the chip (via the software
program), this particular type of ROM is called
EEPROM (electrically erasable programmable
read-only memory)
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Network Adapters (continued)
• Installing and Configuring Network Adapter
Software
• A device driver (sometimes called, simply, a driver)
is software that enables an attached device to
communicate with the computer’s operating system
• Most operating systems come with a multitude
of built-in device drivers
• Each time a computer boots up, the device
drivers for all its connected peripherals are
loaded into RAM so that the computer can
communicate with those devices at any time
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Network Adapters (continued)
• Interpreting LED Indicators
• Most modern NICs have LEDs that indicate whether
or not they’re communicating with the network
• The only way to know for certain what your NIC’s
LEDs are trying to tell you is to read the
documentation
• Your NIC may have one or more of the following
lights, and they may or may not be labeled: ACT,
LNK, TX or RX
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Network Adapters (continued)
• IRQ (Interrupt Request)
• IRQ is a message to the computer that instructs it to
stop what it is doing and pay attention to something
else
• An interrupt is the circuit board wire over which
a device issues voltage to signal this request
• Each interrupt must have a unique IRQ number, a
number that uniquely identifies that component to
the main bus
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Network Adapters (continued)
• If two devices attempt to use the same interrupt,
resource conflicts and performance problems will
result
• If IRQ conflicts do occur, you must reassign a
device’s IRQ
• Network adapter IRQs can also be changed
through the adapter’s EEPROM configuration utility
or through the computer’s CMOS configuration
utility
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Network Adapters (continued)
• CMOS (complementary metal oxide semiconductor)
is a type of microchip that requires very little energy
to operate
• In a PC, the CMOS stores settings pertaining to
a computer’s devices
• These settings are saved even after you turn off
a PC because the CMOS is powered by a tiny
battery in your computer
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Network Adapters (continued)
• Information saved in CMOS is used by the
computer’s BIOS (basic input/output system)
• The BIOS is a simple set of instructions that
enables a computer to initially recognize its
hardware
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Network Adapters (continued)
• Memory Range
• The memory range indicates, in hexadecimal
notation, the area of memory that the network
adapter and CPU will use for exchanging, or
buffering, data
• Some memory ranges are reserved for specific
devices—most notably, the system board
• Reserved address ranges should never be selected
for new devices
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Network Adapters (continued)
• Memory range settings are less likely to cause
resource conflicts than IRQ settings, mainly
because there are more available memory ranges
than IRQs
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Network Adapters (continued)
• Base I/O Port
• The base I/O port setting specifies, in hexadecimal
notation, which area of memory will act as a
channel for moving data between the network
adapter and the CPU
• A device’s base I/O port cannot be used by any
other device
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Network Adapters (continued)
• Firmware Settings
• Transmission characteristics are held in the
adapter’s firmware
• Network adapter configuration utilities allow you to
perform diagnostics
• In order to perform the entire group of the
diagnostic tests on the NIC’s utility disk, you must
have a loopback plug
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Network Adapters (continued)
• A loopback plug (also called a loopback adapter) is
a connector that plugs into a port and crosses over
the transmit line to the receive line so that outgoing
signals can be redirected into the computer for
testing
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Network Adapters (continued)
• Choosing the Right Network Adapter
• compatibility with your existing system
• must match the network’s bus type, access method,
connector types, and transmission speed
• correct drivers available
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Repeaters
• Repeaters are the simplest type of connectivity
devices that regenerate a digital signal
• Repeaters operate in the Physical layer of the OSI
Model
• A repeater contains one input port and one output
port, so it is capable of receiving and repeating
only the data stream
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Repeaters (continued)
• Repeaters are suited only to bus topology
networks
• The advantage to using a repeater is that it allows
you to extend a network inexpensively
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Hubs
• A hub is a repeater with more than one output port
• A simple hub may contain multiple ports
connecting a group of computers in a peer-to-peer
fashion, accepting and repeating signals from
each node
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Hubs (continued)
• A slightly more sophisticated hub may contain
multiple ports for devices and one port that
connects to a network’s backbone
• On Token Ring networks, hubs are called
Multistation Access Units (MAUs)
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Hubs (continued)
• The elements shared by most hubs are
described in the following list:
• Ports—Receptacles where patch cables connect
workstations or other devices to the hub
• Uplink port—The receptacle used to connect one
hub to another hub in a daisy-chain or hierarchical
fashion
• Link LED—The light on a port that indicates
whether it is in use
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Hubs (continued)
• Collision LED (Ethernet hubs only)—The light that
roughly indicates collisions —when one frame
interferes with another’s transmission—by blinking,
usually orange
• Status LED—The light that indicates that the hub is
receiving power
• Power supply—The device that provides power to
the hub
• Ventilation fan—A device used to cool a device’s
internal electronics
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Hubs (continued)
• Types of Hubs
• Standalone hubs, as their name implies, are hubs
that serve a group of computers that are isolated
from the rest of the network or that form their own
small network
• Stackable hubs resemble standalone hubs, but
they are physically designed to be linked with
other hubs in a single telecommunications closet
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Hubs (continued)
• Stackable hubs linked together logically represent
one large hub to the network
• A great benefit to using stackable hubs is that your
network or workgroup does not depend on a single
hub, which could present a single point of failure
• Stackable hubs may support a number of different
media connectors and transmission speeds and
may come with or without special processing
features
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Hubs (continued)
• The simplest type of hubs—known as passive
hubs—do nothing but repeat signals
• Intelligent hubs are also called managed hubs,
because they can be managed from anywhere on
the network
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Bridges
• Bridges are devices that connect two network
segments by analyzing incoming frames and
making decisions about where to direct them
based on each frame’s MAC address
• They have a single input and a single output port
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Bridges (continued)
• They can interpret physical addressing information
• Bridges are protocol-independent
• Bridges can move data more rapidly than
traditional routers
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Bridges (continued)
• Bridges take longer to transmit data than either
repeaters or hubs, because bridges actually
analyze each packet
• Inserting a bridge into a network, you can add
length beyond the maximum limits that apply to
segments
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Bridges (continued)
• Bridges can help improve network performance
because they can be programmed to filter out
certain types of frames
• As nodes transmit data through the bridge, the
bridge establishes a filtering database (also known
as a forwarding table) of known MAC addresses
and their locations on the network
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Switches
• Switches are connectivity devices that subdivide a
network into smaller logical pieces, or segments
• Switches interpret MAC address information
• Most switches have an internal processor, an
operating system, memory, and several ports that
enable other nodes to connect to it
• Because they have multiple ports, switches can
make better use of limited bandwidth and prove
more cost-efficient than bridges
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Switches (continued)
• A collision domain is a logically or physically
distinct Ethernet network segment on which all
participating devices must detect and
accommodate data collisions
• Switches provide at least two advantages: better
security and better performance
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Switches (continued)
• Switches provide separate channels for
(potentially) every device, performance stands to
gain
• Switches can become overwhelmed by
continuous, heavy traffic and then cannot prevent
data loss
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Switches (continued)
• Switches differ in the method of switching they
use—namely, cut-through mode or store and
forward mode
• A switch running in cut-through mode will read a
frame’s header and decide where to forward the
data before it receives the entire packet
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Switches (continued)
• Cut-through switches can detect runts, or
erroneously shortened packets
• Cut-through switches cannot detect corrupt packets
• The most significant advantage of the cut-through
mode is its speed
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Switches (continued)
• In store and forward mode, a switch reads the
entire data frame into its memory and checks it for
accuracy before transmitting the information
• Store and forward switches transmit data more
accurately
• They are more appropriate for larger LAN
environments, because they do not propagate data
errors
• They can also transfer data between segments
running different transmission speeds
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Switches (continued)
• Using Switches to Create VLANs
• Switches can create virtual local area networks
(VLANs), logically separate networks within
networks, by grouping a number of ports into a
broadcast domain
• A broadcast domain is a combination of ports that
make up a Layer 2 segment
• In contrast to a collision domain, ports in the same
broadcast domain do not share a single channel
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Switches (continued)
• VLANs can be designed with flexibility
• They can include ports from more than one switch
or segment
• On a wireless network,VLANs allow mobile clients
to move from one access point’s range to another
without losing network functionality or having to reauthenticate with the network
• VLANs are created by properly configuring a
switch’s software
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Switches (continued)
• Reasons for using VLANs include:
• Separating groups of users who need special
security or network functions
• Isolating connections with heavy or unpredictable
traffic patterns
• Identifying groups of devices whose data should be
given priority handling
• Containing groups of devices that rely on legacy
protocols incompatible with the majority of the
network’s traffic
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Switches (continued)
• Higher-Layer Switches
• A switch capable of interpreting Layer 3 data is
called a Layer 3 switch (and sometimes called a
routing switch)
• A switch capable of interpreting Layer 4 data is
called a Layer 4 switch
• These higher-layer switches may also be called
routing switches or application switches can cost
three times more than Layer 2 switches, and are
typically used as part of a network’s backbone
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Routers
• A router is a multiport connectivity device that
directs data between nodes on a network
• Routers can integrate LANs and WANs running at
different transmission speeds and using a variety
of protocols
• Routers are finding niches in specialized
applications such as linking large Internet nodes
or completing digitized telephone calls
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Routers (continued)
• Routers can also determine the shortest, fastest
path between two nodes
• A typical router has an internal processor, an
operating system, memory, input and output jacks
for different types of network connectors
(depending on the network type), and, usually, a
management console interface
• A router with multiple slots that can hold different
interface cards or other devices is called a modular
router
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Routers (continued)
• A router that directs data between nodes on an
autonomous LAN (or one owned and operated by
a single organization) is known as an interior
router
• Exterior routers direct data between nodes
external to a given autonomous LAN. Routers that
operate on the Internet backbone are exterior
routers
• Between interior and exterior routers are border
routers (or gateway routers)
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Routers (continued)
• Routers may use one of two methods for directing
data on the network: static or dynamic routing
• Static routing is a technique in which a network
administrator programs a router to use specific
paths between nodes
• Dynamic routing, on the other hand, automatically
calculates the best path between two nodes and
accumulates this information in a routing table
• By default,when a router is added to a network,
routing protocols update its routing tables
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Routers (continued)
• Routing Protocols: RIP, OSPF, EIGRP, and BGP
• Best path refers to the most efficient route from one
node on a network to another
• To determine the best path, routers communicate
with each other through routing protocols
• In addition to its ability to find the best path, a
routing protocol can be characterized according to
its router convergence time, the time it takes for a
router to recognize a best path in the event of a
change or network outage
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Routers (continued)
• RIP (Routing Information Protocol) for IP and
IPX—The oldest routing protocol, RIP, which is still
widely used, factors in only the number of hops
between nodes when determining a path from one
point to another
• Routers using RIP broadcast their routing tables
every 30 seconds to other routers, whether or not
the tables have changed
• One advantage to RIP is its stability
• If the number of hops in a path exceeds 15, the
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network destination is considered unreachable
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Routers (continued)
• OSPF (Open Shortest Path First) for IP—This
routing protocol, also used on interior or border
routers, makes up for some of the limitations of
RIP and can coexist with RIP on a network
• OSPF imposes no hop limits on a transmission path
• In OSPF, each router maintains a database of the
other routers’ links, and if notice is received
indicating the failure of a given link, the router can
rapidly compute an alternate path
• It is commonly used on LANs that rely on a mix of
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routers from different manufacturers
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Routers (continued)
• EIGRP (Enhanced Interior Gateway Routing
Protocol) for IP, IPX, and AppleTalk
• It has a fast convergence time and a low network
overhead, and is easier to configure and less CPUintensive than OSPF
• EIGRP also offers the benefits of supporting
multiple protocols and limiting unnecessary network
traffic between routers
• It accommodates very large and heterogeneous
networks, but is only supported by Cisco routers
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Routers (continued)
• BGP (Border Gateway Protocol) for IP—BGP is
the routing protocol of Internet backbones and is
not used to route between nodes on an
autonomous LAN
• The most complex of the routing protocols
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Routers (continued)
• Brouters
• The networking industry has adopted the term
bridge router, or brouter, to describe routers that
take on some characteristics of bridges
• The advantage of crossing a router with a bridge
is that you can forward nonroutable protocols,
such as NetBEUI, plus connect multiple network
types through one device
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Gateways
• In broad terms, they are combinations of
networking hardware and software that connect
two dissimilar kind of networks
• Gateways actually repackage information so that it
can be read by another system
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Gateways
• Gateways can reside on servers, microcomputers,
connectivity devices (such as routers), or
mainframes
• They transmit data more slowly than bridges or
routers because of the complex translations they
conduct
• Slow, gateways have the potential to cause
extreme network congestion
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Gateways (continued)
• Popular types of gateways
• E-mail gateway—A gateway that translates
messages from one type of e-mail system to
another
• IBM host gateway—A gateway that establishes and
manages communication between a PC and an
IBM mainframe computer
• Internet gateway—A gateway that allows and
manages access between LANs and the Internet
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Gateways (continued)
• Popular types of gateways (continued)
• LAN gateway—A gateway that allows segments of
a LAN running different protocols or different
network models to communicate with each other
• Voice/data gateway—A gateway that connects the
part of a network that handles data traffic with the
part of a network that handles voice traffic
• Firewall—A gateway that selectively blocks or filters
traffic between networks
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Summary
• Functions of LAN connectivity hardware
• Install and configure a network adapter
cards
• Identify problems associated with
connectivity hardware
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Summary (continued)
• Describe the factors involved in choosing
a network adapter, hub, switch, or router
• Discuss the functions of repeaters, hubs,
bridges, switches, routers, and gateways,
and the OSI Model layers at which they
operate
• Describe the uses and types of routing
protocols
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