Windows Vista Security: Praxisorientierte Sicherheit für Profis

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Chapter 14: Setting Up Your Network

On a network, private IP addresses are assigned in one of three ways:

Static IP address

A fixed IP address that you manually assign to a computer or device

Dynamic IP address

An IP address automatically assigned to a computer or device by DHCP

Automatic private IP address

An IP address automatically assigned to a computer by the operating system

when a DHCP server cannot be contacted

On a home or small-office network, you can use the DHCP service capability of your

Ethernet router to assign IP addresses. Refer to the user manual of your router to find

the correct procedure to configure the DHCP service to assign IP addresses automati-

cally to computers and devices connecting to your network. Once you’ve configured

the DHCP service, you must configure the network adapters of computers and

devices to use DHCP, which is typically the default IP addressing scheme.

Understanding IPv6

Although IPv4 allows for more than four billion networked computers and devices, the

world is running out of available IPv4 addresses. Rather than allow there to be a short-

age of available addresses, organizations have worked together to create several solu-

tions to the problem. One of these solutions is IPv6. Unlike IPv4, which uses 32-bit

addresses, IPv6 uses 128-bit addresses, which offer literally enough IP addresses so that

there’s one IP address for each square yard of the Earth’s surface. Or put another way,

there are about 340,282,237,000,000,000,000,000,000,000,000,000,000 available

addresses—give or take a few hundred million quadrillion.

To make it easier to track all those IP addresses, IPv6 uses hexadecimal numbers

rather than decimal numbers to define the address space. This means that instead of

allowing only the numbers 0 through 9 for each position in the IP address, IPv6

allows the values 0 through 9 and A through F, with A representing 10, B represent-

ing 11, and so on, up to F representing 15. Thus, the values 0 through 15 can be

represented using the values 0 through F.

IPv6’s 128-bit addresses are divided into eight 16-bit blocks delimited by colons.

With standard IPv6 addresses, the first 64 bits represent the network ID and the last

64 bits represent the network interface being used. Since many IPv6 address blocks

are set to 0, a contiguous set of 0 blocks can be expressed as ::, a notation referred to

as the double-colon notation. Table 14-6 shows an example of an IPv6 IP address

and an abbreviated IP address.

Table 14-6. IPv6 address example

IPv6 address Truncated IPv6 address

FE80:0:0:033C:FB:B335:FE4F:752B FE80::033C:FB:B335:FE4F:752B