Creating a VPC on AWS using Terraform.

Below is a simple example of a Terraform module for creating a VPC in AWS. The module is reusable and accepts input variables to customize the VPC configuration.

First, create a directory for your VPC module, e.g., modules/vpc.

In the modules/vpc directory, create a file named main.tf and add the following contents:

resource "aws_vpc" "this" {
  cidr_block = var.cidr_block
  tags = {
    Name = var.vpc_name
  }
}

resource "aws_subnet" "this" {
  count = length(var.subnet_cidr_blocks)

  cidr_block = var.subnet_cidr_blocks[count.index]
  vpc_id     = aws_vpc.this.id
  tags = {
    Name = "${var.vpc_name}-subnet-${count.index + 1}"
  }
}

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

resource "aws_route_table" "public" {
  vpc_id = aws_vpc.this.id
  tags = {
    Name = "${var.vpc_name}-public-rt"
  }
}

resource "aws_route" "public_internet_gateway" {
  route_table_id         = aws_route_table.public.id
  destination_cidr_block = "0.0.0.0/0"
  gateway_id             = aws_internet_gateway.this.id
}

resource "aws_route_table_association" "public" {
  count = length(var.subnet_cidr_blocks)

  subnet_id      = aws_subnet.this[count.index].id
  route_table_id = aws_route_table.public.id
}

Next, create a file named variables.tf in the same directory to define the input variables:

variable "cidr_block" {
  description = "The CIDR block for the VPC"
  type        = string
}

variable "vpc_name" {
  description = "The name of the VPC"
  type        = string
}

variable "subnet_cidr_blocks" {
  description = "The list of CIDR blocks for the subnets"
  type        = list(string)
}

Now, to use the VPC module in your main Terraform configuration, create a main.tf file at the root level and include the following contents:

module "vpc" {
  source = "./modules/vpc"

  cidr_block         = "10.0.0.0/16"
  vpc_name           = "my-vpc"
  subnet_cidr_blocks = ["10.0.1.0/24", "10.0.2.0/24", "10.0.3.0/24"]
}

This configuration sets up a VPC with a /16 CIDR block, an Internet gateway, a public route table, and three /24 subnets. The module is reusable and can be customized using input variables.

Please note that this is just a simple example, and a production-ready VPC module may include additional resources such as network ACLs, security groups, and NAT gateways.