VPC Module

This Terraform module creates a Virtual Private Cloud (VPC) in AWS with public and private subnets across multiple Availability Zones.

Resources Created

• VPC
• Internet Gateway
• NAT Gateway
• Public and Private Subnets
• Route Tables (Public and Private)

Usage

module "vpc" {
  source = "path/to/vpc/module"

  vpc_cidr             = "10.0.0.0/16"
  public_subnet_cidrs  = ["10.0.0.0/20", "10.0.16.0/20", "10.0.32.0/20"]
  private_subnet_cidrs = ["10.0.48.0/20", "10.0.64.0/20", "10.0.80.0/20"]
  availability_zones   = ["us-west-2a", "us-west-2b", "us-west-2c"]
}

Inputs

Name	Description	Type	Default	Required
vpc_cidr	CIDR block for the VPC	string	"10.0.0.0/16"	no
public_subnet_cidrs	CIDR blocks for public subnets	list(string)	["10.0.0.0/20", "10.0.16.0/20", "10.0.32.0/20"]	no
private_subnet_cidrs	CIDR blocks for private subnets	list(string)	["10.0.48.0/20", "10.0.64.0/20", "10.0.80.0/20"]	no
availability_zones	List of AZ names or IDs in the region	list(string)	n/a	yes
enable_dns_hostnames	Enable DNS hostnames in the VPC	bool	true	no
enable_dns_support	Enable DNS support in the VPC	bool	true	no

3. Architecture Design

Here’s a simple architecture for your VPC:

• VPC (10.0.0.0/16)
  • Public Subnet 1 in AZ1 (10.0.0.0/20)
  • Public Subnet 2 in AZ2 (10.0.16.0/20)
  • Public Subnet 3 in AZ3 (10.0.32.0/20)
  • Private Subnet 1 in AZ1 (10.0.48.0/20)
  • Private Subnet 2 in AZ2 (10.0.64.0/20)
  • Private Subnet 3 in AZ3 (10.0.80.0/20)

4. Additional Components to Consider

• Internet Gateway (IGW): Attach an Internet Gateway to your VPC to allow communication with the internet. Only the public subnets will have routes to the IGW.

• NAT Gateway or NAT Instance: For instances in private subnets that need to access the internet for updates, a NAT Gateway is needed. This NAT Gateway is usually placed in one of the public subnets.

• Route Tables:

  • Public Route Table: Associated with public subnets, contains a route to the IGW.
  • Private Route Table: Associated with private subnets, contains a route to the NAT Gateway.

• Security Groups and Network ACLs: Set up security groups for instances and Network ACLs for the subnets to control traffic at different layers.

5. Implementing the VPC in AWS Console

• Create a VPC with the CIDR block 10.0.0.0/16.
• Create Subnets:
  • 3 Public Subnets with the above CIDRs.
  • 3 Private Subnets with the above CIDRs.
• Attach an Internet Gateway to the VPC.
• Create a NAT Gateway in one of the public subnets.
• Create Route Tables:
  • Public Route Table with a route to the Internet Gateway. Associate it with the public subnets.
  • Private Route Table with a route to the NAT Gateway. Associate it with the private subnets.

Conclusion

This architecture allows you to have a secure and scalable environment in AWS, with segregation of public and private resources. The CIDR blocks are chosen to provide sufficient IP addresses while maintaining easy scalability.