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IP Addressing

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IP Terminology

Throughout this chapter you'll learn several important terms vital to your
understanding of the Internet Protocol. Here are a few to get you started:

Bit A bit is one digit; either a 1 or a 0.

Byte A byte is 7 or 8 bits, depending on whether parity is used. For the
rest of this chapter, always assume a byte is 8 bits.

Octet Always 8 bits. Base-8 addressing scheme.

Network address The designation used in routing to send packets to a
remote network--for example, 10.0.0.0, 172.16.0.0, and 192.168.10.0.

Broadcast address The address used by applications and hosts to send
information to all nodes on a network is called the broadcast address.
Examples include 255.255.255.255, which is all networks, all nodes;
172.16.255.255, which is all subnets and hosts on network 172.16.0.0;
and 10.255.255.255, which broadcasts to all subnets and hosts on net-
work 10.0.0.0.

The Hierarchical IP Addressing Scheme

An IP address consists of 32 bits of information. These bits are divided into
four sections, referred to as octets or bytes, each containing 1 byte (8 bits).
You can depict an IP address using one of three methods:

Dotted-decimal, as in 172.16.30.56

Binary, as in 10101100.00010000.00011110.00111000

Hexadecimal, as in AC 10 1E 38

All these examples represent the same IP address. Although hexadecimal

isn't used as often as dotted-decimal or binary when IP addressing is dis-
cussed, you still might find an IP address stored in hexadecimal in some pro-
grams. The Windows Registry is a good example of a program that stores a
machine's IP address in hex.

The 32-bit IP address is a structured or hierarchical address, as opposed

to a flat or nonhierarchical, address. Although either type of addressing
scheme could have been used, hierarchical addressing was chosen for a good
reason. The advantage of this scheme is that it can handle a large number of
addresses, namely 4.3 billion (a 32-bit address space with two possible

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