Virtual Private Network (VPN) | VPN Technology| VPN Working

Virtual Private Network (VPN) | VPN Technology| VPN Working

Virtual Private Network or VPN is the most popular term among large organizations. It is a kind of private network that provides enough security in cost effective manner. Before discussing virtual private network, let us have some idea about the private network.

Private Network

Private Network is a kind of network designed for use inside an organization. It allows access to shared resources and also provides privacy. A private network that uses internet model must use IP addresses. There are 3 available choices for addressing:

  • The network can apply for a set of addresses from the Internet authorities and use them without being connected to the internet.
  • The network can use any set of addresses without registering with Internet authorities. As the network is isolated, the addresses do not have to be unique.
  • To overcome the problems of about two strategies, internet authorities have reserved 3 sets of addresses. Any organization can use an address from this range.


To achieve privacy, an organization use any of the 3 strategies: the private network, hybrid network or Virtual private network. Virtual Private Network (VPN) overcomes the problem of privacy in private networks inside the organization in cost effective manner. To connect several sites, an organization need several leased lines that cost a lot. Virtual Private Network is a technology that allows organizations to use global internet for both private and public communications.

Why is VPN called Virtual?

VPN Technology creates such a network that is private but virtual. It is private because it maintains privacy inside the organization. It is virtual because it doesn’t use private WANs in reality. These networks are physically public but virtually private that is why it is named so.

How VPN Work?

VPN Technology provides authentication, integrity, and privacy inside the organization by using tunnel mode of IPSec.

In tunnel mode of IPSecurity, each IP datagram destined for private use in the organization is encapsulated in another datagram. To use IPSec in tunneling, the VPNs need to use two sets of addressing.

here is an example for better understanding VPN addressing



The public network (Internet) is responsible for carrying the packet from R1 to R2. Outsiders cannot decipher the content of the packet or the source and the destination addresses. Deciphering/ Decrypting takes place at R2, which finds the destination address of the packet and delivers it.

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