Understanding IP Addressing


Understanding IP Addressing:

Everything You Ever Wanted To Know
The Internet continues to grow at a phenomenal rate. This is reflected in
the tremendous popularity of the World Wide Web (WWW), the opportunities
that businesses see in reaching customers from virtual storefronts,
and the emergence of new ways of doing business. It is clear that expanding
business and public awareness will continue to increase demand for access
to resources on the Internet.
Internet Scaling Problems
Over the past few years, the Internet has experienced two major scaling
issues as it has struggled to provide continuous and uninterrupted
growth:
• The eventual exhaustion of IP version 4 (IPv4) address space
• The need to route traffic between the ever increasing number of networks
that comprise the Internet
The first problem is concerned with the eventual depletion of the IP
address space. IPv4 defines a 32-bit address which means that there are
only 232 (4,294,967,296) IPv4 addresses available. As the Internet continues
to grow, this finite number of IP addresses will eventually be
exhausted.


Classful IP Addressing

When IP was first standardized in September 1981, the specification
required that each system attached to an IP-based Internet be assigned
a unique, 32-bit Internet address value. Systems that have interfaces to
more than one network require a unique IP address for each network
interface. The first part of an Internet address identifies the network on
which the host resides, while the second part identifies the particular
host on the given network. This creates the two-level addressing hierarchy
that is illustrated


Extended Network Prefix

Internet routers use only the network prefix of the destination address
to route traffic to a subnetted environment. Routers within the subnetted
environment use the extended network prefix to route traffic
between the individual subnets. The extended network prefix is composed
of the classful network prefix and the subnet number.