Internet Gateways and NAT Gateways

Understanding how traffic flows between your VPC and the internet is essential. Two components govern this: the Internet Gateway (IGW), which provides full bidirectional internet access for public subnets, and the NAT Gateway, which gives private subnets outbound-only access. This lesson covers both in depth.

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Internet Gateway (IGW)

An Internet Gateway is a horizontally scaled, redundant, and highly available VPC component. It performs two functions:

1. Acts as a target in your route table for internet-routable traffic.
2. Performs Network Address Translation (NAT) between private and public IPv4 addresses for instances with a public IP.

Key Properties

Property	Detail
Scope	One IGW per VPC
Availability	Fully managed, highly available, no bandwidth cap
Cost	No hourly charge — you pay only for data transfer
State	Must be both created and attached to a VPC

How an IGW Works — Step by Step