The VPC Front Door
An internet gateway is the component that connects a VPC to the public internet. Without one attached, nothing inside the VPC can talk to the outside world, no matter how the routes are set.
Two Jobs
An internet gateway does more than just sit between networks.
- It provides a target for route tables that want to reach the internet.
- It performs network address translation for instances that have a public IP address.
- It is horizontally scaled and managed, so it is not a single point of failure.
What It Takes To Be Reachable
A resource reaches the internet through the gateway only when three things line up. It needs a public or elastic IP, a route table entry pointing at the gateway, and security rules that permit the traffic. Missing any one of these breaks connectivity.
Key idea
An internet gateway is the managed, highly available door between a VPC and the internet, and reaching it requires a public address, a route, and permissive security rules together.