What is a VPN?

Let’s say an organization has some resources in its private network. An employee wants to access the resources from his home. Now, the employee cannot do so using the public Internet because the public Internet is unsecured by default. The data transferred over the Internet can be intercepted and read by a malicious third-party. A Virtual Private Network or VPN can extend the organization’s private network across the public Internet so that the employees can access the sensitive resources from the private network securely from any place. An employee can use VPN to access the resources safely as if the device is directly connected to the private network.

In VPN, a VPN tunnel is created first and the data is encrypted and then sent through the VPN tunnel. Also, the user is authenticated before he is provided access to the VPN.

There can be different types of VPN depending on the technologies used, e.g. the tunneling protocol, the type of topology of connections, the levels of security provided, the OSI layer in which it works, the number of simultaneous connections, etc. Depending on the topology of connections, there are two types of VPN – remote-access VPN and site-to-site VPN.

What is a Remote-Access VPN?

In remote-access VPN, client software is used on the VPN user’s device. When the user wants to connect to the VPN, the user’s device connects to a VPN gateway. The VPN gateway acts as one end of a VPN tunnel.

The VPN gateway authenticates the user and after successful authentication, a VPN tunnel is created. After that, when the user tries to transfer any data, the user’s device encrypts the data and sends it across the VPN tunnel. Similarly, when the user receives any data, the user’s device decrypts the data and reads it.

As the data transferred to and from the user’s device is encrypted and then transferred through the VPN tunnel, a malicious third-party cannot read the data even if he manages to intercept it. As a result, the user can safely access the resources from the private network from any place using the public Internet.

What is a Site-to-Site VPN?

Unlike remote-access VPN, a site-to-site VPN is used to connect different LANs of an organization. Let’s say an organization has different branch offices in different geographical locations. Different branch offices use different LANs. And, the organization wants to connect the LANs securely using the public Internet so that any employee can access resources from any LAN of any branch office securely. The organization, in that case, can use site-to-site VPN.

In site-to-site VPN, the VPN gateway from one LAN communicates with the VPN gateway of another LAN and …