Networking With Vista P2

1 Computer Computer Switch Computer FIGURE 1.9 You can use a switch as the central connection point for your network.. To join the two segments, you have three choices: ■ Many older swit

network segment, a collection of network devices connected to a single switch.

(If this network segment comprises your entire network, you can call it a

switched network.)

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Computer

Computer

Switch

Computer

FIGURE 1.9

You can use a switch as the central connection point for your network.

The switch then forwards data from one network node to another On basic

switches such as the type used in homes or small offices, the switch usually

reads the MAC address of the destination node in each ethernet frame and

sends the frame directly to that device Most switches maintain a switching

table, a record of the MAC addresses and network port numbers used by each

device on the network As you use your network, the switch makes note of

each new MAC address and adds it to the switching table, which improves

overall switch performance

You can also use a switch to send data across multiple network segments For

example, you might have a network segment in one room or office and a

sec-ond segment in the room or office next door Similarly, if your network

out-grows your original switch, you might add a second switch to the network

instead of upgrading to a switch with more ports To join the two segments,

you have three choices:

■ Many older switches come with a special uplink port that’s designed to

connect two switches by running a

network cable from the uplink port

of one switch to the uplink port of

the other switch On some of these

switches, a button controls whether

the port is used as a regular RJ-45

port or an uplink port

The network config-uration shown in Fig-ure 1.9—that is, multiple network nodes joined to a central connec-tion point—is called the star topology

note

■ Use an ethernet crossover cable to link two switches by running the cable from any port in the first switch to any port in the second switch

■ Get switches where the ports support Auto Crossover (also called Auto MDI/MDI-X crossover detection; MDI stands for Medium-Dependent Interface) This enables you to connect two switches without using an

uplink port or a crossover cable

As with NICs and cables, all switches support one or more of the ethernet standards For example, a Fast Ethernet switch will almost always support 10/100 connections, whereas a Gigabit Ethernet switch will usually support 10/100/1000 connections Make sure you match your switch to the ethernet standard you’re using on your network

Understanding Routers

You saw in the previous section that a switch forwards ethernet packets according to the device MAC address in the frame header This works extremely well, and most modern switches are high-performance devices However, the inherent limitation of a switch becomes obvious when you want

to add an Internet connection to your network:

■ When you want to request data from a web server, it’s impossible to know the MAC address of the remote server computer, so the switch has no way to forward the data request

■ When a web server wants to send data to your computer, it’s impossi-ble for the remote machine to know your computer’s MAC address, so the switch cannot get the data to your computer

In other words, the MAC address-based forwarding performed by a switch is

limited to LAN traffic and cannot be used to handle WAN (wide area network)

data

To solve this problem, you need to add a router to your network (see Figure

1.10) A router is a device that makes decisions about where to send the net-work packets it receives So far, this sounds

suspiciously similar to a switch The major difference is that while a switch uses a MAC address-based switching table to

for-ward data, a router uses a routing table that tracks IP addresses, unique addresses

assigned to every Internet host and to

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A wide area network

is network that cov-ers a wide geographical area Some corporations use wide area networks, but the Internet is the wide area network

note

every computer on your network For example, this is useful when the

com-puters share a high-speed Internet connection, because the router ensures that

the Internet data goes to the computer that requested it To make this work,

you plug your high-speed modem directly into the special WAN port in the

back of the router

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FIGURE 1.10

You add a router to your network when you want to add Internet access.

Understanding IP Addresses

An IP address is a 32-bit value assigned to a computer by a network

adminis-trator or, if you’ve signed up for an Internet account, by your Internet service

provider (ISP) As you’ll see in a minute, these addresses are designed so that

every host and router on the Internet or within a network has a unique

address That way, when an application needs to send data to a particular

locale, it knows that the destination address it plops into the packet header

will make sure that everything ends up where it’s supposed to

The problem with IP addresses is their “32-bitness.” Here’s an example:

Not very inviting, is it? To make these numbers easier to work with, you use

dotted-decimal notation (also known in the trade as dotted-quad notation) This notation

divides the 32 bits of an IP address into four groups of 8 bits each (each of these

groups is called a quad), converts each

group into its decimal equivalent, and then separates these numbers with dots

Let’s look at an example Here’s the previ-ous IP address grouped into four 8-bit quads:

11001101 11010000 01110001 00000010 Now you convert each quad into its decimal equivalent When you do, you end up with this:

11001101 11010000 01110001 00000010

205 208 113 2 Now you insert dots between each decimal number to get the dotted-decimal form of the address:

205.208.113.2

The Router and Dynamic IP Addressing

The MAC addresses of network devices are assigned in advance by the device manufacturer How, then, are IP addresses assigned? For the servers and other remote machines you deal with on the Internet, each network that wants on the Internet must sign up with a domain registrar (such as VeriSign.com or Register.com) In turn, the registrar assigns that network a block of IP addresses that the administrator can then dole out to each computer (or, in the case of an ISP, to each customer)

For your own network, however, the IP addresses are assigned as follows:

■ Your router is given its own IP address—called the public IP address—

from the pool of addresses controlled by your ISP Internet data sent to any computer on your network is first sent to the router’s external IP address

■ The computers on your network are assigned IP addresses In other words, when a computer logs on to the network, it is assigned an IP

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You can convert a value from binary to decimal using Windows Vista’s Calculator Select Start, All Programs, Acces-sories, Calculator, and then, in the Calculator window, select View, Scientific Click the Bin (binary) option, use the text box to type the 1s and 0s of the binary value you want to convert, and click the Dec (decimal) option

tip

address from a pool of available

addresses When the computer logs

off, the address it was using is

returned to the pool The system

that manages this dynamic

alloca-tion of addresses is called the

Dynamic Host Configuration Protocol

(DHCP), and the computers or devices that implement DHCP are called

DHCP servers In most home networks, the router acts as a DHCP server.

In most cases, the range of addresses is from 192.168.1.1 to 192.168.1.254

(On some routers, the range is from 192.168.0.1 to 192.168.0.254.) The router

itself usually takes the 192.168.1.1 address (this is called its private IP address),

and the pool of possible addresses is usually some subset of the total range,

such as between 192.168.1.100 and 192.168.1.150

The big advantage of this setup is that your network is never exposed to the

Internet All communication goes through the router’s public IP address; so as

far as, say, a web or email server is concerned, it’s communicating with a

device at that address The router is able to get the correct data to your

com-puter because when you initially request data, it adds your comcom-puter’s private

IP address and the number of the communications port your computer is

using and stores this data in a routing table When data comes back from the

Internet, the router converts the public destination IP address of the data to

the private address of your computer, a process known as network address

translation (NAT).

The Router as Firewall

On a small network, the main function of a router is to be used as a gateway

between your network and the Internet Through the magic of NAT, your

net-work cannot be seen from any device attached to the Internet; as far as the

Internet is concerned, your network is nothing but a router (For this reason,

an Internet-connected router that performs NAT duties is sometimes called an

edge router.) NAT, therefore, acts as a kind of simple firewall, a technology that

prevents unwanted data from reaching a network

However, most modern routers go one step further and come with separate

firewall software This gives you an interface for controlling and managing

the firewall, which mostly means opening and closing specific software ports

used by applications For example, you’ll see in Chapter 19, “Setting Up a

Website,” that to successfully use a web server on your network you need to

configure the router’s firewall to allow incoming connections on port 80

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When a device such

as a router is set up

as the sole connection point between a network and the Internet, that device is called a gateway

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The Router as Switch

You’ve seen that a router can act as a gateway device and a firewall device, but there’s a third hat that’s worn by most modern routers: a switch device A typical router has a few RJ-45 ports (usually four; see Figure 1.11); so, as with

a dedicated switch, you can create ethernet connections for computers and other devices by running ethernet cable from each device to a router port

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WAN port (for broadband modem) RJ-45 ports

FIGURE 1.11

Most routers have built-in switches, meaning you can use the router’s ports to connect devices

to your network.

This means that if you have a small ethernet network, you might be able to get away with using just a router as your network’s connection point Figure 1.12 shows this network configuration

On the other hand, if your network is larger or if you have a number of other devices you need to connect, your router might not have enough ports

Similarly, you may be upgrading your network to Gigabit Ethernet and your router only comes with Fast Ethernet (or 10/100) ports In both cases, the easiest solution is to leave your existing router in place and add to the network a dedi-cated switch that meets your needs In this scenario, you connect the broad-band modem to the router’s WAN port, you run a network cable from one of the router’s RJ-45 ports to an RJ-45 port on the switch, and you connect your network devices to the switch Figure 1.13 shows this network configuration

FIGURE 1.12

A small ethernet network can use a single router as both the gateway and the switch.

1

Computer

Computer

Router Cable/DSL Modem

Computer Internet

Computer

Computer

Router Cable/DSL Modem

Computer

Internet

Switch

FIGURE 1.13

Larger ethernet networks may require a dedicated switch as the central network connection point.

Understanding Other Ethernet Devices

To round out your look at ethernet hardware, the next few sections give you a quick overview of a few other devices you can connect to your ethernet net-work

Network Attached Storage

A network attached storage (NAS) device contains one or more hard drives and

plugs into a switch or router This enables the client computers on the network

to store files on the device rather than on a network share If you have one or two internal hard drives lying around, you can purchase just the NAS enclo-sure and attach the drives yourself In this case, make enclo-sure that the NAS enclosure’s interface supports your hard drive type (for example, ATA versus SATA)

Many NAS devices also come with one or more USB ports, which means you can expand the device’s storage space by attaching one or more external USB hard drives Figure 1.14 shows a typical NAS enclosure

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FIGURE 1.14

With a NAS enclosure, you attach one or more internal and external hard drives that a network computer can then access directly.

Print Server

To print over the network, you normally share a printer that’s attached to one

of the network computers However, this requires that the computer with the

printer share that printer, it requires each person who wants to use the printer

to connect to it, and it requires that the network computer always be on

These aren’t onerous demands, but they sometimes create enough of a hassle

to make network administrators turn to dedicated print servers, devices that

connect printers directly to the network

In some cases, a printer comes with a built-in RJ-45 port, so you need only run

ethernet cable from the printer to an RJ-45 port in the switch or router

However, most consumer-grade printers don’t have a built-in NIC In that

case, you can get a print server that’s a separate box with either a parallel

port or a USB port (or both), as well as an RJ-45 port (see Figure 1.15) You

connect the printer to the print server’s parallel or USB port, and then connect

the print server’s RJ-45 port to the switch or router

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FIGURE 1.15

A print server device enables you to connect a printer directly to the network without having

to share it through a network computer.

Digital Media Receiver

Windows Vista programs such as Windows Media Player and Windows Media Center can broadcast digital media over an ethernet connection This is called

streaming the media, and the data itself is called a stream Other Windows

Vista computers on your network can pick up and play that stream However,

you can also use a device called a digital media receiver (DMR) to access a

media stream being sent over an ethernet connection and then play that stream through connected equipment such as speakers, audio receivers, or a

TV Examples of DMRs include the Xbox 360, the Roku SoundBridge, and the D-Link MediaLounge Other DMR types include certain digital media players (such as MP3 players) and digital picture frames, which display images streamed over a network connection

Powerline Adapter

You use a powerline adapter to connect a computer to your network using the

AC power lines in your home or office This device isn’t a NIC per se Instead,

it acts as a kind of bridge that connects a regular ethernet NIC to your net-work without having to connect that NIC directly to a switch or router You actually need at least two powerline adapters One adapter plugs into an AC outlet near your switch or router, and you then run ethernet cable from the switch/router to the powerline adapter, which effectively connects your home

or office power lines to the network You then plug a second powerline adapter into an AC outlet near the device you want to network, and you run an ether-net cable from the device’s NIC to the powerline adapter You can repeat this for any number of devices

A Buyer’s Guide to Ethernet Hardware

If you’re looking to purchase new ethernet hardware, whether you’re starting from scratch or looking to upgrade your existing equipment, the buying process is not always easy because you often face a thicket of jargon terms and a list of product specifications that seems to require an advanced degree

in electrical engineering to figure out To make it easier to choose the right ethernet hardware, the next few sections give you a few pointers on what to look for and what to avoid when purchasing the four main hardware types: NICs, cables, switches, and routers

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