Securing Communication between Data Centre and Cloud

In the early days of my career, I used to wonder why we connect to office network using the crypto card.  If you have no clue or some clue about what the hell is VPN (just like me :D) ; I would recommend this link which covers the fundamentals of VPN. 

Let's start with definition of VPN gateway-

VPN Gateway

A VPN gateway is a type of networking device that connects two or more devices or networks together in a VPN infrastructure. It is designed to create connection or communication between two or more remote sites, networks or devices and/or connect multiple VPNs together. Ref

From the Perspective of Cloud

Companies are gradually moving (their systems) to cloud, so there is need of secure connectivity between Data Centre and Cloud hosted applications. Cloud has become a logical extension of the corporate datacenter (this is referred to as hybrid datacenter). 

The cloud hosted application should be able to securely talk to in-premise data or application. This is where the VPN gateway comes into play by securing one site to another site. VPN builds a secure tunnel between two remote sites.

Below diagram shows VPC inside AWS and GCP. You can think of VPC (Virtual Private Cloud) as a cloud inside cloud; or a logical datacenter inside AWS (or GCP - Google Cloud Platform). 

Traffic traveling between the two networks is encrypted by originator's VPN gateway, then it gets decrypted by the receiver's VPN gateway.