Overview
An Internet Gateway (IGW) serves two purposes: to provide a target in your VPC route tables for internet-routable traffic, and to perform network address translation (NAT) for instances that have been assigned public IPv4 addresses.
Key Characteristics
- Bidirectional: Allows both inbound and outbound traffic (if permitted by security groups and NACLs).
- Managed Service: The cloud provider handles the scaling and availability of the gateway.
- Public Subnet Requirement: For a subnet to be 'public,' it must have a route to an Internet Gateway.
Importance
IGWs are the primary way to connect a VPC to the public internet, enabling web servers and other public-facing resources to function.