What is the use of an Internet Gateway?
The use of an internet gateway is to allow resources such as EC2 instances access to the internet. For example you may have a VPC and a public subnet within it. To allow your subnet to have access to the internet you can use an internet gateway. AWS allows public subnets to access the internet with an internet gateway and with private subnets the Internet is accessed through a NAT gateway being placed in a public subnet.
Common Questions
Can resources on the internet initiate connections to my EC2 instance through an internet gateway?
An internet gateway allows two-way traffic between the internet and resources in a public subnet.
What is a NAT gateway?
A NAT gateway is a managed AWS service that lets resources in a private subnet start outbound connections to the internet or other external networks, while blocking unsolicited inbound connections from those external networks. A NAT gateway is like a middleman that lets private EC2 instances go out to the internet without exposing them to direct incoming internet traffic.
Real life use cases?
A public web server. If you run a website on EC2 and users on the internet need to reach it, the EC2 instance or load balancer sits in a public subnet that routes to an internet gateway. AWS’s VPC planning examples explicitly describe putting internet-facing web servers in subnets that receive traffic from clients on the internet.
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