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173
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PPENDIX
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I
P Addresses, Network Masks and Subnets
IP Addresses
Note:
T
his section pertains only to IP addresses
for IPv4 (version 4 of the Internet Protocol).
IPv6 addresses are not covered.
This section assumes basic knowledge of
binary numbers, bits, and bytes. For details
on this subject, see Appendix B on page 179.
IP addresses, the Internet's version of telephone numbers,
are used to identify individual nodes (computers or devices)
on the Internet. Every IP address contains four numbers, each
from 0 to 255 and separated by dots (periods), e.g. 20.56.0.211.
These numbers are called, from left to right, field1, field2, field3,
and field4.
This style of writing IP addresses as decimal numbers separated
by dots is called dotted decimal notation. The IP address
20.56.0.211 is read "twenty dot fifty-six dot zero dot two-eleven."
Structure of an IP address
IP addresses have a hierarchical design similar to that of
telephone numbers. For example, a 7-digit telephone number
starts with a 3-digit prefix that identifies a group of thousands
of telephone lines, and ends with four digits that identify one
specific line in that group.
Similarly, IP addresses contain two kinds of information.
•
Network ID: identifies a particular network within the Internet
or intranet.