06. Internet Gateway

Internet Gateway

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Prerequisites

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1. Internet Gateway

Internet Gateway is a core component of AWS networking. It enables Communication between your VPC and the Internet

An Internet Gateway (IGW) is:

• A gateway attached to a VPC
• A bridge between private AWS network and public internet

👉 Without IGW:

• VPC is private
• EC2 cannot access internet
• External users cannot access EC2

Your VPC is completely isolated from the internet

• Horizontally scaled (no bottleneck)
• Highly available
• Managed by AWS
• No additional cost

2. How to work IGW

Internet
   ↓
[ Internet Gateway ]
   ↓
[ Public Subnet ]
   └── EC2 (Web Server)
   ↓
[ Private Subnet ]
   └── RDS / Backend

2-1. VPC

Internet Gateway must be attached to VPC.

2-2. Subnet

A subnet is public if it has a route to an Internet Gateway. NOT Private Subnet.

2-3. Route Table

Route Table must allow internet traffic.

• Example: All outbound traffic goes to the internet

Destination: 0.0.0.0/0
Target: Internet Gateway

2-4. Public IP

Instance must have Public IP. Public IPv4 or Elastic IP required

2-5. Security Group

Security Group must allow traffic

Example:

• Port 22 (SSH)
• Port 80 (HTTP)

3. How to create IGW

3-1. Search VPC

3-2. Click Navigation pane → “Internet gateways”

3-3. Click Button → “Create internet gateway”

3-4. Internet gateway settings

3-5. Attach VPC

4. Related Concepts

• Components
  • VPC
  • Public Subnet
  • Router table
  • Nat Gateway