Default VPC overview in AWS - Mini Project: Build & Apply

Default VPC overview

📖 Scenario: You are starting to learn about AWS networking. Every AWS account has a default Virtual Private Cloud (VPC) that lets you launch resources easily without extra setup.Think of the default VPC as a ready-made neighborhood where your cloud computers can live and talk to each other right away.

🎯 Goal: Build a simple AWS CloudFormation template that defines a default VPC with its main components: subnets, internet gateway, and route table. This will help you understand how a default VPC is structured.

📋 What You'll Learn

Create a VPC resource with the default CIDR block 172.31.0.0/16

Add two public subnets in different availability zones

Attach an Internet Gateway to the VPC

Create a route table with a route to the Internet Gateway

Associate the route table with the public subnets

💡 Why This Matters

🌍 Real World

Default VPCs let you quickly launch cloud resources without manual network setup. Understanding their structure helps you customize your cloud network safely.

💼 Career

Cloud engineers and architects often work with VPCs to design secure and scalable cloud networks. Knowing default VPC components is foundational.

1

Create the VPC resource

Create a resource called DefaultVPC of type AWS::EC2::VPC with the property CidrBlock set to "172.31.0.0/16".

AWS

# Create the DefaultVPC resource here

Need a hint?

The VPC resource needs a CidrBlock property with the value "172.31.0.0/16".

2

Add two public subnets

Add two resources called PublicSubnet1 and PublicSubnet2 of type AWS::EC2::Subnet. Set their VpcId to { Ref: DefaultVPC }. Use CidrBlock values "172.31.0.0/20" and "172.31.16.0/20" respectively. Set AvailabilityZone to "us-east-1a" and "us-east-1b" respectively.

AWS

Resources:
  DefaultVPC:
    Type: AWS::EC2::VPC
    Properties:
      CidrBlock: "172.31.0.0/16"

# Add PublicSubnet1 and PublicSubnet2 resources here

Need a hint?

Each subnet needs VpcId, CidrBlock, and AvailabilityZone properties.

3

Add Internet Gateway and Route Table

Add a resource called InternetGateway of type AWS::EC2::InternetGateway. Then add a resource called VPCGatewayAttachment of type AWS::EC2::VPCGatewayAttachment that attaches InternetGateway to DefaultVPC. Next, add a resource called PublicRouteTable of type AWS::EC2::RouteTable with VpcId set to { Ref: DefaultVPC }. Finally, add a resource called PublicRoute of type AWS::EC2::Route with RouteTableId set to { Ref: PublicRouteTable }, DestinationCidrBlock set to "0.0.0.0/0", and GatewayId set to { Ref: InternetGateway }.

AWS

Resources:
  DefaultVPC:
    Type: AWS::EC2::VPC
    Properties:
      CidrBlock: "172.31.0.0/16"

  PublicSubnet1:
    Type: AWS::EC2::Subnet
    Properties:
      VpcId: { Ref: DefaultVPC }
      CidrBlock: "172.31.0.0/20"
      AvailabilityZone: "us-east-1a"

  PublicSubnet2:
    Type: AWS::EC2::Subnet
    Properties:
      VpcId: { Ref: DefaultVPC }
      CidrBlock: "172.31.16.0/20"
      AvailabilityZone: "us-east-1b"

# Add InternetGateway, VPCGatewayAttachment, PublicRouteTable, and PublicRoute resources here

Need a hint?

Remember to attach the Internet Gateway to the VPC and create a route to allow internet traffic.

4

Associate route table with public subnets

Add two resources called SubnetRouteTableAssociation1 and SubnetRouteTableAssociation2 of type AWS::EC2::SubnetRouteTableAssociation. Set their SubnetId to { Ref: PublicSubnet1 } and { Ref: PublicSubnet2 } respectively. Set their RouteTableId to { Ref: PublicRouteTable }.

AWS

Resources:
  DefaultVPC:
    Type: AWS::EC2::VPC
    Properties:
      CidrBlock: "172.31.0.0/16"

  PublicSubnet1:
    Type: AWS::EC2::Subnet
    Properties:
      VpcId: { Ref: DefaultVPC }
      CidrBlock: "172.31.0.0/20"
      AvailabilityZone: "us-east-1a"

  PublicSubnet2:
    Type: AWS::EC2::Subnet
    Properties:
      VpcId: { Ref: DefaultVPC }
      CidrBlock: "172.31.16.0/20"
      AvailabilityZone: "us-east-1b"

  InternetGateway:
    Type: AWS::EC2::InternetGateway

  VPCGatewayAttachment:
    Type: AWS::EC2::VPCGatewayAttachment
    Properties:
      VpcId: { Ref: DefaultVPC }
      InternetGatewayId: { Ref: InternetGateway }

  PublicRouteTable:
    Type: AWS::EC2::RouteTable
    Properties:
      VpcId: { Ref: DefaultVPC }

  PublicRoute:
    Type: AWS::EC2::Route
    Properties:
      RouteTableId: { Ref: PublicRouteTable }
      DestinationCidrBlock: "0.0.0.0/0"
      GatewayId: { Ref: InternetGateway }

# Add SubnetRouteTableAssociation1 and SubnetRouteTableAssociation2 resources here

Need a hint?

Each subnet needs to be associated with the public route table to enable internet access.