How to Create a VPC Environment Using CloudFormation (Template File)

In this article, I’m going to talk about how to write a template file that’s necessary to execute CloudFormation.

What is CloudFormation？

It is a service for managing and developing yml.json formatted resources presented by AWS.

You can start, stop, and delete the AWS resources in a unit of stacks from a single console rather than managing from individual consoles.

It costs for EC2 instances that are created by CloudFormation, but there is no extra charge for CloudFormation itself.

Building VPC

Now, let’s create VPC based on the following yml file using CloudFormation.

vpc.yml

---
AWSTemplateFormatVersion: '2010-09-09'
  
# Parameter setting
Parameters:
  # Enter each identifiers
  ProjectCode:
    Type: String
    Default: test
    Description: Project Code
　# Enter VPC’s CIDR
  VPCCidr:
    Type: String
    Default: 10.31.0.0/16
    Description: VPCCidr
  # Enter subnet’s CIDR
  PublicSubnetCidr:
    Type: String
    Default: 10.31.0.0/24
    Description: PublicSubnetCidr
 
Resources:
# Around VPC
  #VPC settings
  VPC:
    Type: AWS::EC2::VPC
    Properties:
      CidrBlock: !Ref VPCCidr
      Tags:
        - Key: Name
          Value: !Join [ "-", [ !Ref ProjectCode, vpc ] ]
 
  # InternetGateway settings
  InternetGateway:
    Type: AWS::EC2::InternetGateway
    Properties:
      Tags:
        - Key: Name
          Value: !Join [ "-", [ !Ref ProjectCode, igw ] ]
  AttachGateway:
    Type: AWS::EC2::VPCGatewayAttachment
    Properties:
      VpcId: !Ref VPC
      InternetGatewayId: !Ref InternetGateway
  PublicRouteTableIGW:
    Type: AWS::EC2::RouteTable
    DependsOn: AttachGateway
    Properties:
      VpcId: !Ref VPC
      Tags:
        - Key: Name
          Value: !Join [ "-", [ !Ref ProjectCode, public-route-table-igw ] ]
  PublicRouteIGW:
    Type: AWS::EC2::Route
    DependsOn: AttachGateway
    Properties:
      RouteTableId: !Ref PublicRouteTableIGW
      DestinationCidrBlock: 0.0.0.0/0
      GatewayId: !Ref InternetGateway
 
  # Subnet settings
  PublicSubnet:
    Type: AWS::EC2::Subnet
    DependsOn: AttachGateway
    Properties:
      VpcId: !Ref VPC
      AvailabilityZone: ap-northeast-1a
      CidrBlock: !Ref PublicSubnetCidr
      Tags:
        - Key: Name
          Value: !Join [ "-", [ !Ref ProjectCode, public-subnet ] ]

Description of each contents

Let me describe the above yml file.

---
AWSTemplateFormatVersion: '2010-09-09'

It shows the format version of the CloudFormations template.

# Parameter setting

Parameters:
  # Enter each identifiers
  ProjectCode:
    Type: String
    Default: test
    Description: Project Code
　# Enter VPC’s CIDR
  VPCCidr:
    Type: String
    Default: 10.31.0.0/16
    Description: VPCCidr
  # Enter subnet’s CIDR
  PublicSubnetCidr:
    Type: String
    Default: 10.31.0.0/24
    Description: PublicSubnetCidr

When you want to create each resource, it is also ok to set the same value all the time but you may also want to change the value to make the operation easier.

In CloudFormation, it allows you to change the value however you like in the “Parameters” section.

In the sample file, it sets a common identifier for each resource as a ProjectCode, and the initial value is set, but you can change them with a stack as you wish.

The CIDR for VPC and subnets are also set as initial values, but same as the sample file, the values can also be changed with units of stack.

Resources:
# Around VPC
  #VPC setting
  VPC:
    Type: AWS::EC2::VPC
    Properties:
      CidrBlock: !Ref VPCCidr
      Tags:
        - Key: Name
          Value: !Join [ "-", [ !Ref ProjectCode, vpc ] ]

The section that manages AWS resources is the above “Resources”.

The VPC part is called the logical ID which can be referred to optional ones and it also can be referred from other resources.

However, each logical ID needs to be unique otherwise an error will occur when it’s executed.

The “Type: “ part defines the actual AWS resource.

Under the “Properties” is the configuration part of the VPC which calls VPCCidr parameters that have been set earlier with the function Ref, calls the predefined CIDR, and inserts it into the CidrBlock.

I’m setting only CidrBlock this time, but the detailed settings are mentioned in the AWS official documentation that you can take a look at.

AWS official “AWS::EC2::VPC”

Also, I added the name tag in the tags section for clarity.

This one also uses a function called Join to attach the -vpc tag to the Value part.

AttachGateway:
  Type: AWS::EC2::VPCGatewayAttachment
  Properties:
    VpcId: !Ref VPC
    InternetGatewayId: !Ref InternetGateway
PublicRouteTableIGW:
  Type: AWS::EC2::RouteTable
  DependsOn: AttachGateway
  Properties:
    VpcId: !Ref VPC
    Tags:
      - Key: Name
        Value: !Join [ "-", [ !Ref ProjectCode, public-route-table-igw ] ]
PublicRouteIGW:
  Type: AWS::EC2::Route
  DependsOn: AttachGateway
  Properties:
    RouteTableId: !Ref PublicRouteTableIGW
    DestinationCidrBlock: 0.0.0.0/0
    GatewayId: !Ref InternetGateway
 
# Subnet settings
PublicSubnet:
  Type: AWS::EC2::Subnet
  DependsOn: AttachGateway
  Properties:
    VpcId: !Ref VPC
    AvailabilityZone: ap-northeast-1a
    CidrBlock: !Ref PublicSubnetCidr
    Tags:
      - Key: Name
        Value: !Join [ "-", [ !Ref ProjectCode, public-subnet ] ]

For the other resources, they are also declared in the same way with “Type: ” and detailed settings are made in the “Properties”, and the Name tag is associated with each resource.

Summary

In this article I talked about how to write a template file necessary to build a VPC.

I’d like to explain the execution part in the next article because it’ll be very long.

You have to manually set up AWS resources on a daily basis, but using these tools can reduce the effort you spend.

Since this tool is free to use, I strongly recommend it if you use AWS frequently.

This blog post is translated from a blog post written by Junichiro Okazaki on our Japanese website Beyond Co..