Internet Gateway

💡 Definition

An Internet Gateway (IGW) is a horizontally scaled, redundant, and highly available VPC component that allows communication between your VPC and the internet.

🔑 Key Concepts

• Internet Connectivity: Enables resources in public subnets of a VPC to connect to the internet.
• Public IP Addresses: Necessary for EC2 instances to have a public IP address (or Elastic IP) to communicate with the internet.
• Route Table Entry: For internet-bound traffic, a Route Table must have a route to the Internet Gateway.

⚙️ How it Works

1. Create IGW: You create an Internet Gateway.
2. Attach to VPC: You attach the Internet Gateway to your VPC.
3. Update Route Table: Add a route to the public subnet's Route Table that directs internet-bound traffic (0.0.0.0/0) to the Internet Gateway.

🎯 Use Cases

• Public-Facing Applications: Allowing web servers in public subnets to serve traffic to the internet.
• Outbound Internet Access: Enabling EC2 instances in public subnets to initiate connections to the internet.

💰 Pricing Model

• Free: The Internet Gateway itself is free. You are charged for data transfer.

📝 Exam Tips (CLF-C02)

• Must be attached to a VPC.
• A VPC can only have one Internet Gateway.
• It's a component that enables public internet connectivity for your VPC.
• Not a firewall; security is handled by Security Groups and NACLs.

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See Also: * VPC * Route Table * NAT Gateway (for private subnet internet access)