What is VPN (Virtual Private Network)

A virtual private network (‘VPN’) is a network technology, extends a private network over a public network, and allow you to creates a protected, secure and encrypted connection over a less secure network or public internet, such as the internet.



Big organization, government institutes, educational institutes, mostly use this technology to allow remote users and geographically separated offices to securely access to a corporate applications and secure their communications. To make sure the communication is secure over VPN, communicated data in encrypted form moves the through secure tunnels and VPN users must use some kind authentication methods such as token, password or personal identification number to gain access to VPN.

And the individual internet users may use VPN to browse securely, protect personal identity and make themselves completely anonymous over internet, secure their transactions, unblock blocked sites, circumvent geo-restrictions and censorship.

Type of VPN

  • Remote-access VPN
  • Site-to-Site VPN

1- Remote-Access VPN

VPN enables individual remote users to securely access to their home or organizations’s network by using common public network such as internet, while traveling. It establish a secure connection with remote computer network. An example of a organization that require a remote-access VPN is a large firm with numbers of salespeople in the field.


Remote-access VPN


There following components are require in a remote access VPN

  • Network Access Server (NAS)
  • Client Software

Network Access Server (NAS)

Alternative names are media gateway and remote access server (RAS). A NAS might be a dedicated server or might be an applications operating on a shared server. To access the VPN, NAS user connect form the internet and provide valid credentials to sign in. NAS use its own authentication process to authenticate the user’s credentials — it might be on the same server or use the separate authentication server.

Client Software

The second required component in Remote access VPN is client software. The VPN users who want to access the VPN they must have required software in their computers to establish and maintain connection to VPN. Most of the operating system come with built-in software that can easily connect to remote access VPN, but there are some VPNs that require specific software to install on client computer. The client software sets a communication tunnel to NAS. The software also encrypts the communication to keep it secure.
Big organization with hundreds of staff members use this type of VPN, they purchase their own remote access VPN. But some organization outsource their remote-access VPN service through an enterprice service provider (ESP).

2- Site-to-Site VPN

Site-to-Site VPN enables an organization’s multiple offices on different locations to establish a secure communication connection with each other while using a public network. It extends the organization’s network and make available computer resources from one location to other. Organization having their
branch offices around the world use this type of VPN.

There are two types of Site-to-Site VPN.

  • Intranet VPN
  • Extranet VPN

Intranet VPN



If an organization have one or more remote-offices, branch offices or corporate headquarters and they want to create a single private network. Intranet link them over a shared infrastructure using dedicated connections. It helps to reduce the WAN bandwidth cost and provide ease to connect new sites.

Extranet VPN



If you want to securely share part of business’s information with your suppliers, customers, partners or vendors, then extranet VPN allows you to securely share business related information and work together with other companies using dedicated connections.

Requirements of VPN



The idea behind the Virtual Private Network is tunneling, tunneling responsible to create and maintain logical network connection. This network connection takes the packets that built in specific VPN protocol type are encapsulated within other packet before it’s transported over the internet. The outer one protects the inner packet from public access and also ensure that the packet moving within a tunnel. For more info….

There are the two VPN tunneling types.

Types of Tunneling

  • Voluntary
  • Compulsory

Types of VPN Protocols

  • žPoint-to-Point Tunneling Protocol (PPTP)
  • Layer Two Tunneling Protocol (L2TP)
  • Internet Protocol Security (IPsec)


Encryption is the practice of encoding information and to ensure that the computer with the right decoder will be able to use the including information. The encryption can be used for the  protection of files or email you send to others. For more info about encryption

Flowing are the the most commonly used forms of encryption.

Types Of Encryption

  • symmetric-key encryption
  • public-key Encryption



žVirtual private network (VPN) connections are only accepted for those users and routers that have been authorized. This authorization determined by user account and remote access policies.

žThere are 3 levels of Authentication.

Levels of Authentication

  • User-level Authentication
  • Data origin authentication and data integrity
  • Computer-Level Authentication


An firewall uses packet filtering to permit or disallow the stream of specific kinds of traffic. IP address packet filtering offers an easy method that you specify what ip address traffic is permitted to cross the firewall. For more info about VPN firewall

Approaches to using a firewall with a VPN Server

  • VPN Server behind the firewall
  • VPN Server in front of the firewall

Advantages of VPN

  • Security
    • Protects you data while it is on public network
  • Reliability
    • User can remotely access the VPN without any trouble at any time.
  • Privacy Protection
    • anonymity over internet
  • Unblock blocked Site
  • Cost Saving
    • eliminating the need for expensive long-distance leased lines.
    • Operational costs
    • VPN maintenance cost is very low
  • Change Location/ IP Address

Disadvantages of VPN

  • Require Expert level Knowledge about VPN technology to set up and maintain a virtual private network
  • Reliability and performance of internet base VPN relies on ISP. This mean it is not under an organization’s direct control.





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