isabella232 / terraform-aws-ha-vpc-module

Terraform module containing a highly available AWS VPC

Terraform AWS HA VPC Module

This Terraform module creates a full-fledged highly available AWS VPC. The intention of this module is to deploy a straight-forward highly available IPv4 VPC without too much hassle.

Features

• Public subnets in every availability zone
• Private subnets in every availability zone
• NAT gateway in every availability zone
• Internet gateway
• Custom configured route table for public subnets
• Custom configured route tables for every private subnet

Usage

module "aws_ha_vpc" {
  source = "github.com/binxio/terraform-aws-ha-vpc-module"

  cidr_block = "10.0.0.0/20"
  subnet_newbits = 4
  tags = {
    Key = "Value"
  }
}

How subnets are calculated

We create a public and private availability zone in every availability zone of a particular region (the private subnets are created on top of the already calculated public subnet cidr ranges). To calculate the cidr block of a subnet, we use the following formula:

cidrsubnet(var.cidr_block, var.subnet_newbits, availability_zone_count)

Consider a region with 3 availability zones and a VPC with the range 10.0.0.0/20.

The cidr block ranges of the public subnets are:

> cidrsubnet("10.0.0.0/20", 3, 0)
"10.0.0.0/23"
> cidrsubnet("10.0.0.0/20", 3, 1)
"10.0.2.0/23"
> cidrsubnet("10.0.0.0/20", 3, 2)
"10.0.4.0/23"

The cidr block ranges of the private subnets are:

> cidrsubnet("10.0.0.0/20", 3, 3)
"10.0.6.0/23"
> cidrsubnet("10.0.0.0/20", 3, 4)
"10.0.8.0/23"
> cidrsubnet("10.0.0.0/20", 3, 5)
"10.0.10.0/23"

Requirements

No requirements.

Providers

Name	Version
aws	4.2.0

Modules

No modules.

Resources

Name	Type
aws_eip.ngws	resource
aws_internet_gateway.igw	resource
aws_nat_gateway.ngw	resource
aws_route.igw	resource
aws_route.ngw	resource
aws_route_table.private_crt	resource
aws_route_table.public_crt	resource
aws_route_table_association.private_subnets	resource
aws_route_table_association.public_subnets	resource
aws_subnet.private_subnet	resource
aws_subnet.public_subnet	resource
aws_vpc.main	resource
aws_availability_zones.available	data source
aws_region.current	data source

Inputs

Name	Description	Type	Default	Required
cidr_block	Classless Inter-Domain Routing (CIDR) block	string	n/a	yes
enable_dns_support	Enable DNS support	bool	true	no
enable_dns_hostnames	Enable DNS hostnames	bool	false	no
subnet_newbits	Subnet mask bits	string	n/a	yes
tags	Tags that will be applied to all resources	map(any)	{}	no

Outputs

Name	Description
vpc_id	Outputs the unique VPC identifier
public_subnet_ids	Outputs the public subnet identifiers
private_subnet_ids	Outputs the private subnet identifiers