Public and Private Network Address

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 : to

Class B : 128 .0.0.0 to

Class C : to

Class D: : to

Class E : : to

For each class, there is a Private IP address:

Class A : to PA : to

Class B : 128 .0.0.0 to PA : to

Class C : to PA : to

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

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