The hosts that populate that network share those
same bits, but each host is identi?¬?ed by the uniqueness of the remaining bits. Like a group
of houses along the same road, the street address is the same, but the house number is
unique.
Figure 1-27 illustrates a sample IP addressing scheme in an internetwork.
Figure 1-27 IP Addressing
The IP address is 32 bits in length and is binary in nature, but it is expressed in a format
that can be easily understood by the human brain. Basically, the 32 bits are broken into
4 sections of 8 bits each, known as octets or bytes. Each of these octets is then converted
into decimal numbers between 0 and 255, and each octet is separated from the following
one by dots. Figure 1-28 illustrates the format of an IP address using 172.16.122.204 as an
example.
172.17.0.1
172.18.0.2
172.17.0.2 192.168.1.1
192.168.1.0 10.13.0.0
10.13.0.1
172.16.0.2
172.18.0.1 172.16.0.1
46 Chapter 1: Building a Simple Network
Figure 1-28 IP Address Format
The IP address format is known as dotted decimal notation. Figure 1-28 shows how the
dotted decimal address is derived from the 32-bit binary value:
?– Sample address: 172.16.122.204.
?– Each bit in the octet has a binary weight (such as 128, 64, 32, 16, 8, 4, 2, and 1), and
when all the bits are on, the sum is 255.
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