All IPv4 address can be divided into two categories:

• Public and
• Private

Public IP address:

• These address are meant for the external world that is for the internet.
• These are also known as WAN address.
• These address are routed on the internet.

Private IP address:

• These address are not seen on the internet that is they are reserved for internal use behind a router or or other NAT devices.
• They are also referred as local IP address.
• They are used within a particular organization or a network(LAN) and cannot be used to communicate with the internet that is with external world.
• This is one of the solution to overcome with the depletion of IPv4 addresses.

Classful IP address:

In classful address, there are five classes that is

Class A : 0.0.0.0 to 127.255.255.255

Class B : 128 .0.0.0 to 192.255.255.255

Class C : 192.0.0.0 to 223.255.255.255

Class D: : 224.0.0.0 to 239.255.255.255

Class E : : 224.0.0.0 to 255.255.255.255

For each class, there is a Private IP address:

Class A : 0.0.0.0 to 127.255.255.255 PA : 10.0.0.0 to 10.255.255.255

Class B : 128 .0.0.0 to 192.255.255.255 PA : 172.16.0.0 to 172.31.255.255

Class C : 192.0.0.0 to 223.255.255.255 PA : 192.168.0.0 to 192.168.255.255

Example of Private IP address:

• Consider a organisation system with Private IP address and a NAT router which translate these private IP address to companies single public IP address used for connecting to external world.
• Again for response these this public IP address are translated to specific private IP address
• On the NAT router there is a mapping for internal Private IP address along with the Port used for application(PAT)

Categories: Networking