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Chapter 5 - IP Addresses, Network Masks, & Subnets
ASUS GigaX 1024i+
This section pertains only to IP addresses for IPv4 (version 4 of the
Internet Protocol). IPv6 addresses are not covered.
5 IP Addresses, Network Masks & Subnets
5.1 IP Addresses
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.”
5.1.1 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.
•
Host ID
: Identifies a particular computer or device on the network.
The first part of every IP address contains the network ID, and the rest of
the address contains the host ID. The length of the network ID depends on
the network’s class (see following section). Table 8 shows the structure of
an IP address.
This section assumes basic knowledge of binary numbers, bits, and
bytes.
