Difference between Public and Private IP Addresses

An IP address is a unique numeric identifier assigned to each machine or host on an Internet.  It designates the specific location of a device on network.

Public IP Addresses:

A unique Internet Protocol (IP) address known as a Public IP address, any computer accessing a public network like Internet must have a unique IP address. Such a host is termed as public host. IP address of the public host is termed as public IP address. The IP addressing scheme makes it possible for hosts to “locate each other” online and exchange information between them.

In IPv4 version, Public IP addresses are classified as below.

• Class A  :  10.0.0.0       to   127.255.255.255
• Class B  :  128.0.0.0     to   191.255.255.255
• Class C  :  192.0.0.0     to   223.255.255.255

Note: Few IP addresses are reserved for private networks from above classes, those are called as private IP addresses.

Private IP Addresses:

The total IP addresses available are very limited. So it is not possible to assign unique IP address to all computers in the Internet world. Here comes the importance of private IP address. The following ranges of IP addresses reserved to use on a private network but they are not routable through the Internet. This is designed for the purpose of creating a measure of valuable security, saves valuable IP address space.

• Class A  :  10.0.0.0        to   10.255.255.255
• Class B  :  172.16.0.0     to   172.31.255.255
• Class C  :  192.168.0.0   to   192.168.255.255

Inside a LAN or private network computers can use these private IP addresses. Two different private networks may use the same set of private IP addresses. These private IP address hosts can access Internet or a public network through a public IP address host by using Network Address Translation (NAT) which is allow us to convert many private IP address can use one real time pubic IP address. That is the private IP address host’s identity will not be visible in the public network, but it shows only the IP address of the public IP address host through which it is connected to the internet. That is Private host shows the IP address of the public host in the Internet environment, but in the local network it shows the private IP address.