Every host on a network
requires a unique IP address. This is easily manageable in a small network but
not a network as large as the Internet. The Internet Assigned Numbers Authority
(IANA) is responsible for managing and distributing IP addresses. The IANA has
created 5 address registrars in five locations of the world. ISPs and large
organizations purchase the addresses from these registrars. The end user in
turn gets the IP address from the ISP. These purchasable IP addresses are
called public addresses and are routable on the Internet. Every host
on the Internet has one of these addresses, in theory.
The IANA also designated a
range of addresses in class A, B and C for use in private networks. These
addresses can be used by anyone within their network without any required
permission but these addresses are not routable on the Internet. You ISP or your
organization usually assigns you one of these addresses and later translates it
to a public address when you want to get out to the Internet. The designated
ranges for private IP addresses are:
Class A – 10.0.0.0 to
10.255.255.255 (1 network)
Class B – 172.16.0.0 to 172.31.255.255 (16 networks)
Class C – 192.168.0.0 to 192.168.255.255 (256 networks)
Class B – 172.16.0.0 to 172.31.255.255 (16 networks)
Class C – 192.168.0.0 to 192.168.255.255 (256 networks)