Internet Gateway for public access in AWS - Step-by-Step Execution

Process Flow - Internet Gateway for public access

Create VPC

↓

Create Internet Gateway

↓

Attach Internet Gateway to VPC

↓

Create Public Subnet in VPC

↓

Update Route Table

↓

Add Route: 0.0.0.0/0 -> Internet Gateway

↓

Launch Public Resources

↓

Resources have public internet access

This flow shows how to create and attach an Internet Gateway to a VPC, then update routing so public subnet resources can access the internet.

Execution Sample

AWS

resource "aws_vpc" "main" {
  cidr_block = "10.0.0.0/16"
}

resource "aws_internet_gateway" "gw" {
  vpc_id = aws_vpc.main.id
}

resource "aws_route_table" "public" {
  vpc_id = aws_vpc.main.id

  route {
    cidr_block = "0.0.0.0/0"
    gateway_id = aws_internet_gateway.gw.id
  }
}

This code creates a VPC, an Internet Gateway attached to it, and a route table with a route sending all internet traffic to the gateway.

Process Table

Step	Action	Resource Created/Updated	State Change	Result
1	Create VPC	aws_vpc.main	VPC with CIDR 10.0.0.0/16 created	VPC ready
2	Create Internet Gateway	aws_internet_gateway.gw	IGW created but not attached	IGW exists
3	Attach IGW to VPC	aws_internet_gateway.gw	IGW attached to VPC	VPC has IGW
4	Create Route Table	aws_route_table.public	Route table created for VPC	Route table ready
5	Add Route 0.0.0.0/0 -> IGW	aws_route_table.public	Route added to send all traffic to IGW	Public route active
6	Associate Route Table with Subnet	aws_route_table_association.public_assoc	Subnet uses public route table	Subnet routes internet traffic
7	Launch Public Resources	EC2 instances in public subnet	Resources get public IP and route	Resources have internet access
8	End	-	-	Internet Gateway setup complete

💡 All steps complete, public subnet resources can access the internet via the Internet Gateway

Status Tracker

Variable	Start	After Step 1	After Step 3	After Step 5	After Step 7	Final
VPC	None	Created with CIDR 10.0.0.0/16	Attached IGW	Route table created	Subnet associated	Ready with IGW and routes
Internet Gateway	None	Created	Attached to VPC	Route added to route table	Used by subnet	Active for internet access
Route Table	None	None	Created	Route 0.0.0.0/0 -> IGW added	Associated with subnet	Routes internet traffic
Subnet	None	None	None	None	Created and associated	Public subnet with internet access

Key Moments - 3 Insights

Why do we need to attach the Internet Gateway to the VPC?

Attaching the Internet Gateway to the VPC (Step 3) connects the VPC to the internet. Without this, the gateway exists but cannot route traffic for the VPC, so public access won't work.

What happens if we don't add the route 0.0.0.0/0 to the Internet Gateway?

Without the route (Step 5), the subnet's traffic won't know to use the Internet Gateway to reach the internet. So even if the gateway is attached, resources won't have internet access.

Why associate the route table with the subnet?

Associating the route table with the subnet (Step 6) tells the subnet to use the routes defined, including the internet route. Without this, the subnet uses the default route table which may not have internet access.

Visual Quiz - 3 Questions

Look at the execution table, at which step is the Internet Gateway attached to the VPC?

A Step 2

B Step 5

C Step 3

D Step 6

💡 Hint

Check the 'Action' and 'State Change' columns in the execution table rows.

According to the variable tracker, what is the state of the Route Table after Step 5?

A Route 0.0.0.0/0 -> IGW added

B Route table created with no routes

C Route table associated with subnet

D Route table deleted

💡 Hint

Look at the 'Route Table' row under 'After Step 5' in the variable tracker.

If the route 0.0.0.0/0 -> IGW was missing, what would be the result?

A Internet Gateway would not be created

B Subnet traffic would not reach the internet

C Resources still have internet access

D VPC would be deleted

💡 Hint

Refer to the key moment about the importance of the route in the execution table step 5.

Concept Snapshot

Internet Gateway connects a VPC to the internet.
Create IGW, attach to VPC.
Add route 0.0.0.0/0 in route table pointing to IGW.
Associate route table with public subnet.
Resources in subnet get internet access.

Full Transcript

This visual execution shows how to set up an Internet Gateway for public access in AWS. First, a VPC is created with a CIDR block. Then an Internet Gateway is created and attached to the VPC. A route table is created and a route is added to send all internet traffic (0.0.0.0/0) to the Internet Gateway. This route table is associated with a public subnet. Finally, resources launched in this subnet receive public IPs and can access the internet through the Internet Gateway. Key points include attaching the gateway to the VPC, adding the correct route, and associating the route table with the subnet to enable internet access.