Create a VPC Through Terraform (Fully Automated Script)

Description.

Terraform is a tool for building infrastructure with various technologies including Amazon AWS, Microsoft Azure, Google Cloud, and vSphere.

Here is a simple document on how to use Terraform to build an AWS VPC along with private/public Subnet and Network Gateway's for the VPC. We will be making 1 VPC with 6 Subnets: 3 Private and 3 Public, 1 NAT Gateways, 1 Internet Gateway, and 2 Route Tables all the creation was automated with appending to your values.

Features

• Fully Automated (included terraform installation)
• Easy to customise and use as the Terraform modules are created using variables,allowing the module to be customized without altering the module's own source code, and allowing modules to be shared between different configurations.
• Each subnet CIDR block created automatically using cidrsubnet Function (Automated)
• AWS informations are defined using tfvars file and can easily changed (Automated/Manual)
• Project name is appended to the resources that are creating which will make easier to identify the resources.

Prerequisites for this project

• Need a IAM user access with attached policies for the creation of VPC.
• Knowledge to the working principles of each AWS services especially VPC, EC2 and IP Subnetting.

How to use

yum install git unzip -y
git clone https://github.com/ykhsupport/terraform_vpc.git
cd terraform_vpc
chmod +x setup.sh
sh setup.sh

setup.sh script sample screenshots

• Screenshot 1
• Screenshot 2
• Screenshot 3
• Screenshot 4

Used Languages

• Bash (scripting)
• Terraform (iaac)

Behind the script

Terraform Installation and VPC creation code and explanation :

please note that you can use the below steps to make a vpc through terraform (Manually).

If you need to download terraform (Manually), then click here Terraform .

Prerequisites

• Create an IAM user on your AWS console that have access to create the required resources.
• Create a dedicated directory where you can create terraform configuration files.
• Terraform Installation steps, click here Terraform installation

sample installation steps

wget https://releases.hashicorp.com/terraform/0.15.3/terraform_0.15.3_linux_amd64.zip
unzip terraform_0.15.3_linux_amd64.zip 
ls -l
-rwxr-xr-x 1 root root 79991413 May  6 18:03 terraform  <<=======
-rw-r--r-- 1 root root 32743141 May  6 18:50 terraform_0.15.3_linux_amd64.zip
mv terraform /usr/bin/
which terraform 
/usr/bin/terraform

Lets create a file for declaring the variables.This is used to declare the variable and the values are passing through the terrafrom.tfvars file.

Create a variables.tf file

variable "region" {}
variable "access_key" {}
variable "secret_key" {}
variable "vpc_cidr" {}
variable "project" {}

Create a provider.tf file

provider "aws" {
  region     = var.region
  access_key = var.access_key
  secret_key = var.secret_key
}

Create a terraform.tfvars

By default terraform.tfvars will load the variables to the the reources. You can modify accordingly as per your requirements.

region     = "put-your-region-here"
access_key = "put-your-access-key-here"
secret_key = "put-your-secret-key-here"
project = "name-of-your-project"
vpc_cidr = "X.X.X.X/X"

Go to the directory that you wish to save your tfstate files.Then Initialize the working directory containing Terraform configuration files using below command.

terraform init

Lets start creating main.tf file with the details below.

To create VPC

resource "aws_vpc" "vpc" {
  cidr_block           = var.vpc_cidr
  instance_tenancy     = "default"
  enable_dns_support   = true
  enable_dns_hostnames = true
  tags = {
    Name = "${var.project}-vpc"
  }
}

To Gather All Subent Name

data "aws_availability_zones" "available" {
  state = "available"
}

To create InterGateWay For VPC

resource "aws_internet_gateway" "igw" {
  vpc_id = aws_vpc.vpc.id
  tags = {
    Name = "${var.project}-igw"
  }
}

Here in this infrastructre we shall create 3 public and 3 private subnets in the region.This sample was meant for regions having 6 availability zone. I have used "us-east-1". Choose your region and modify according to the availability of the AZ. Also we have already provided the CIDR block in our terraform.tfvars you dont need to calculate the subnets, here we use terraform to automate the subnetting in /19.

Creating public1 Subnet

resource "aws_subnet" "public1" {
    
  vpc_id                   = aws_vpc.vpc.id
  cidr_block               = cidrsubnet(var.vpc_cidr, 3, 0)
  availability_zone        = element(data.aws_availability_zones.available.names,0)
  map_public_ip_on_launch  = true
  tags = {
    Name = "${var.project}-public1"
  }
}

Creating public2 Subnet

resource "aws_subnet" "public2" {
  vpc_id                   = aws_vpc.vpc.id
  cidr_block               = cidrsubnet(var.vpc_cidr, 3, 1)
  availability_zone        = element(data.aws_availability_zones.available.names,1)
  map_public_ip_on_launch  = true
  tags = {
    Name = "${var.project}-public2"
  }
}

Creating public3 Subnet

resource "aws_subnet" "public3" {
  vpc_id                   = aws_vpc.vpc.id
  cidr_block               = cidrsubnet(var.vpc_cidr, 3, 2)
  availability_zone        = element(data.aws_availability_zones.available.names,2)
  map_public_ip_on_launch  = true
  tags = {
    Name = "${var.project}-public-3"
  }
}

Creating private1 Subnet

resource "aws_subnet" "private1" {
  vpc_id                   = aws_vpc.vpc.id
  cidr_block               = cidrsubnet(var.vpc_cidr, 3, 3)
  availability_zone        = element(data.aws_availability_zones.available.names,3)
  map_public_ip_on_launch  = true
  tags = {
    Name = "${var.project}-private1"
  }
}

Creating private2 Subnet

resource "aws_subnet" "private2" {
  vpc_id                   = aws_vpc.vpc.id
  cidr_block               = cidrsubnet(var.vpc_cidr, 3, 4)
  availability_zone        = element(data.aws_availability_zones.available.names,4)
  map_public_ip_on_launch  = true
  tags = {
    Name = "${var.project}-private2"
  }
}

Creating private3 Subnet

resource "aws_subnet" "private3" {
  vpc_id                   = aws_vpc.vpc.id
  cidr_block               = cidrsubnet(var.vpc_cidr, 3, 5)
  availability_zone        = element(data.aws_availability_zones.available.names,5)
  map_public_ip_on_launch  = true
  tags = {
    Name = "${var.project}-private3"
  }
}

Creating Elastic IP For Nat Gateway

resource "aws_eip" "eip" {
  vpc      = true
  tags     = {
    Name = "${var.project}-eip"
  }
}

Attaching Elastic IP to NAT gateway

resource "aws_nat_gateway" "nat" {
  allocation_id = aws_eip.eip.id
  subnet_id     = aws_subnet.public1.id
  tags = {
    Name = "${var.project}-nat"
  }
}

Creating Public Route Table

resource "aws_route_table" "public" {
  vpc_id = aws_vpc.vpc.id
  route {
    cidr_block = "0.0.0.0/0"
    gateway_id = aws_internet_gateway.igw.id
  }
  tags = {
    Name = "${var.project}-public"
  }
}

Creating Private Route Table

  resource "aws_route_table" "private" {
  vpc_id = aws_vpc.vpc.id
  route {
    cidr_block = "0.0.0.0/0"
    nat_gateway_id = aws_nat_gateway.nat.id
  }
  tags = {
    Name = "${var.project}-private"
  }
}

Creating Public Route Table Association

resource "aws_route_table_association" "public1" {        
  subnet_id      = aws_subnet.public1.id
  route_table_id = aws_route_table.public.id
}
resource "aws_route_table_association" "public2" {      
  subnet_id      = aws_subnet.public2.id
  route_table_id = aws_route_table.public.id
}
resource "aws_route_table_association" "public3" {       
  subnet_id      = aws_subnet.public3.id
  route_table_id = aws_route_table.public.id
}

Creating Private Route Table Association

resource "aws_route_table_association" "private1" {        
  subnet_id      = aws_subnet.private1.id
  route_table_id = aws_route_table.private.id
}
resource "aws_route_table_association" "private2" {      
  subnet_id      = aws_subnet.private2.id
  route_table_id = aws_route_table.private.id
}
resource "aws_route_table_association" "private3" {       
  subnet_id      = aws_subnet.private3.id
  route_table_id = aws_route_table.private.id
}

Create an output.tf for getting terrafrom output.

output "aws_eip" {
value = aws_eip.eip.public_ip
}
output "aws_vpc" {
value = aws_vpc.vpc.id
}
output "aws_internet_gateway" {
value = aws_internet_gateway.igw.id
}
output "aws_nat_gateway" {
value = aws_nat_gateway.nat.id
}
output "aws_route_table_public" {
value = aws_route_table.public.id
}
output "aws_route_table_private" {
value = aws_route_table.private.id
}

Lets validate the terraform files using

terraform validate

Lets plan the architecture and verify once again.

terraform plan

Lets apply the above architecture to the AWS.

terraform apply

---

Conclusion

Here is a simple document on how to use Terraform to build an AWS VPC along with private/public Subnet and Network Gateway's for the VPC. We will be making 1 VPC with 6 Subnets: 3 Private and 3 Public, 1 NAT Gateways, 1 Internet Gateway, and 2 Route Tables all the creation was automated with appending to your values.

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