Reference Guide for the Model RH340 Internet Access ISDN Router
7-2
Basic Routing Information
IP Addresses and the Internet
Because TCP/IP networks are interconnected widely across the world, every machine on the
Internet must have a unique address to make sure that transmitted data reaches the correct
destination. Blocks of addresses are assigned to organizations by the Internet Assigned Numbers
Authority (IANA). Individual users and small organizations may obtain their addresses either from
the IANA or from an Internet service provider (ISP).
The Internet Protocol (IP) uses a 32-bit address structure. The address is usually written in dot
notation (also called dotted-decimal notation), in which each group of eight bits is written in
decimal form, separated by decimal points. For example, the binary address:
11000011 00100010 00001100 00000111
is normally written as:
195.34.12.7
which is easier to remember and easier to enter into your computer.
In addition, the 32 bits of the address are subdivided into two parts. The first part of the address
identifies the network, and the second part identifies the host node or station on the network. The
dividing point may vary depending on the address range and the application.
There are five standard classes of IP addresses. These address classes have different ways of
determining the network and host sections of the address, allowing for different numbers of hosts
on a network. Each address type begins with a unique bit pattern, which is used by the TCP/IP
software to identify the address class. After the address class has been determined, the software
can correctly identify the host section of the address. The three main address classes are illustrated
in
Figure 7-1
, which shows the network and node sections of the address for each address type.
