VPN Essentials:
- A virtual private network enables the abililty to extend a subnet from one geographic location to another geographic location on two separate networks.
- Extending the subnets allows the network at location "A" to communicate internally with all resources at location "B".
- This is essentially "extending" the on-premise network to the cloud, or the cloud to the on-premise network.
- For AWS, this allows us to communicate with all resources (like an EC2 instance) internally without the need for public IP addresses and an internet gateway.
- It also provides an additional level of security by ensuring that traffic sent using the VPN is encrypted.
- The VPN connection has two parallel routs (IPsec tunnels), which is for redundancy.
- Only one Virtual Private Gateway can be attached to a VPC (just like only one IGW can be attached to a VPC).
- A VPC can have both a VPG and an IGW attached at the same time.
Virtual Private Gateway(VPG):
- A virtual private gateway acts as the "connector" on the VPC (AWS) side of the VPN connection.
- The VPG is connected to the VPC.
NOTE: Both a VPG and a Customer Gateway are required to establish a VPN connection.
Customer Gateway:
- A customer gateway is a physical device or software application at the on-premise location that acts as the "connector" to the VPN connection.
- In your AWS account, the customer gateway component is where you configure the public IP (internet routable static IP) address of the physical device or software application at the on-premise location.
NOTE: Both a VPG and a Customer Gateway are required to establish a VPN connection.
VPN Connection:
- The VPN connection is the actual link between the virtual private gateway and the customer gateway.
- This connection is setup and managed in AWS.
- Each connection uses two IPsec tunnels for redundancy.
Router:
- AWS has dispensed with the concept of having users physically setup and manage a "router".
- However, it is important to understand that route tables are actually part of a "router" assigned to your VPC.
- when setting up a VPN, the route table (for the subnet you wish to extend) must include routes for the on-premise network that are used by the VPN, and point them to the Virtual Private Gateway.