network chapter 5: networking hardware

Chapter 5: Networking Hardware

Network+ Guide to Networks

Third Edition

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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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• 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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• PCI (Peripheral Component Interconnect) is a 32- or 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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• 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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• A newer version of the PCI standard is PCI Express, which specifies a 64-bit bus with a 133-MHz 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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• 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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• 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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• 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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• 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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• 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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• 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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• 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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• 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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• 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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• 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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• 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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• 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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• 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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• 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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• 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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• 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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• 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 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

Repeaters

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• Repeaters are suited only to bus topology networks

• The advantage to using a repeater is that it allows you to extend a network inexpensively

Repeaters (continued)

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• 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

Hubs

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• 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)

Hubs (continued)

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• 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

Hubs (continued)

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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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• 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

Hubs (continued)

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• 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

Hubs (continued)

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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 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

Bridges

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• They can interpret physical addressing information

• Bridges are protocol-independent

• Bridges can move data more rapidly than traditional routers

Bridges (continued)

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• 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

Bridges (continued)

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• 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

Bridges (continued)

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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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• 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

Switches (continued)

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• 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 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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• 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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• 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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• 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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• 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 re-authenticate with the network

• VLANs are created by properly configuring a switch’s software


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• 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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• 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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• 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

Routers

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• 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

Routers (continued)

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• 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)

Routers (continued)

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• 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

Routers (continued)

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• 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

Routers (continued)

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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 network destination is considered unreachable

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• 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 routers from different manufacturers

Routers (continued)

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• 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 CPU-intensive 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

Routers (continued)

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• 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

Routers (continued)

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• 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

Routers (continued)

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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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• 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

Gateways (continued)

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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

network chapter 5: networking hardware

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