README.yaml

#
# This is the canonical configuration for the `README.md`
# Run `make readme` to rebuild the `README.md`
#

# Name of this project
name: terraform-aws-multi-az-subnets
# Tags of this project
tags:
  - aws
  - terraform
  - terraform-modules
  - networking
  - multi-az-subnets
  - subnet
  - private-subnets
  - multi-az
  - nat-gateways
  - subnet-ids
  - cidr
  - dynamic
  - subnet-calculator
# Categories of this project
categories:
  - terraform-modules/networking
# Logo for this project
#logo: docs/logo.png

# License of this project
license: "APACHE2"
# Canonical GitHub repo
github_repo: cloudposse/terraform-aws-multi-az-subnets
# Badges to display
badges:
  - name: Latest Release
    image: https://img.shields.io/github/release/cloudposse/terraform-aws-multi-az-subnets.svg?style=for-the-badge
    url: https://github.com/cloudposse/terraform-aws-multi-az-subnets/releases/latest
  - name: Last Updated
    image: https://img.shields.io/github/last-commit/cloudposse/terraform-aws-multi-az-subnets.svg?style=for-the-badge
    url: https://github.com/cloudposse/terraform-aws-multi-az-subnets/commits
  - name: Slack Community
    image: https://slack.cloudposse.com/for-the-badge.svg
    url: https://slack.cloudposse.com

# List any related terraform modules that this module may be used with or that this module depends on.
related:
  - name: "terraform-aws-named-subnets"
    description: "Terraform module for named subnets provisioning."
    url: "https://github.com/cloudposse/terraform-aws-named-subnets"
  - name: "terraform-aws-dynamic-subnets"
    description: "Terraform module for public and private subnets provisioning in existing VPC"
    url: "https://github.com/cloudposse/terraform-aws-dynamic-subnets"
  - name: "terraform-aws-vpc"
    description: "Terraform Module that defines a VPC with public/private subnets across multiple AZs with Internet Gateways"
    url: "https://github.com/cloudposse/terraform-aws-vpc"
  - name: "terraform-aws-cloudwatch-flow-logs"
    description: "Terraform module for enabling flow logs for vpc and subnets."
    url: "https://github.com/cloudposse/terraform-aws-cloudwatch-flow-logs"
# Short description of this project
description: |-
  Terraform module for multi-AZ [`subnets`](http://docs.aws.amazon.com/AmazonVPC/latest/UserGuide/VPC_Subnets.html) provisioning.

  The module creates private and public subnets in the provided Availability Zones.

  The public subnets are routed to the Internet Gateway specified by `var.igw_id`.

  `nat_gateway_enabled` flag controls the creation of NAT Gateways in the public subnets.

  The private subnets are routed to the NAT Gateways provided in the `var.az_ngw_ids` map.

  If you are creating subnets inside a VPC, consider using [cloudposse/terraform-aws-dynamic-subnets](https://github.com/cloudposse/terraform-aws-dynamic-subnets) instead.

# How to use this project
usage: |-
  ```hcl
  locals {
    public_cidr_block  = cidrsubnet(var.cidr_block, 1, 0)
    private_cidr_block = cidrsubnet(var.cidr_block, 1, 1)
  }

  module "vpc" {
    source = "cloudposse/vpc/aws"
    # Cloud Posse recommends pinning every module to a specific version
    # version = "x.x.x"

    namespace  = var.namespace
    stage      = var.stage
    name       = var.name
    cidr_block = var.cidr_block
  }

  module "public_subnets" {
    source = "cloudposse/multi-az-subnets/aws"
    # Cloud Posse recommends pinning every module to a specific version
    # version = "x.x.x"

    namespace           = var.namespace
    stage               = var.stage
    name                = var.name
    availability_zones  = ["us-east-2a", "us-east-2b", "us-east-2c"]
    vpc_id              = module.vpc.vpc_id
    cidr_block          = local.public_cidr_block
    type                = "public"
    igw_id              = module.vpc.igw_id
    nat_gateway_enabled = "true"
  }

  module "private_subnets" {
    source = "cloudposse/multi-az-subnets/aws"
    # Cloud Posse recommends pinning every module to a specific version
    # version = "x.x.x"

    namespace          = var.namespace
    stage              = var.stage
    name               = var.name
    availability_zones = ["us-east-2a", "us-east-2b", "us-east-2c"]
    vpc_id             = module.vpc.vpc_id
    cidr_block         = local.private_cidr_block
    type               = "private"

    az_ngw_ids = module.public_subnets.az_ngw_ids
  }
  ```
examples: |-
  Given the following configuration

  ```hcl
  module "vpc" {
    source = "cloudposse/vpc/aws"
    # Cloud Posse recommends pinning every module to a specific version
    # version = "x.x.x"

    namespace  = var.namespace
    name       = "vpc"
    stage      = var.stage
    cidr_block = var.cidr_block
  }

  locals {
    public_cidr_block  = cidrsubnet(module.vpc.vpc_cidr_block, 1, 0)
    private_cidr_block = cidrsubnet(module.vpc.vpc_cidr_block, 1, 1)
  }

  module "public_subnets" {
    source = "cloudposse/multi-az-subnets/aws"
    # Cloud Posse recommends pinning every module to a specific version
    # version = "x.x.x"

    namespace           = var.namespace
    stage               = var.stage
    name                = var.name
    availability_zones  = ["us-east-2a", "us-east-2b", "us-east-2c"]
    vpc_id              = module.vpc.vpc_id
    cidr_block          = local.public_cidr_block
    type                = "public"
    igw_id              = module.vpc.igw_id
    nat_gateway_enabled = "true"
  }

  module "private_subnets" {
    source = "cloudposse/multi-az-subnets/aws"
    # Cloud Posse recommends pinning every module to a specific version
    # version = "x.x.x"

    namespace           = var.namespace
    stage               = var.stage
    name                = var.name
    availability_zones  = ["us-east-2a", "us-east-2b", "us-east-2c"]
    vpc_id              = module.vpc.vpc_id
    cidr_block          = local.private_cidr_block
    type                = "private"
    az_ngw_ids          = module.public_subnets.az_ngw_ids
  }

  output "private_az_subnet_ids" {
    value = module.private_subnets.az_subnet_ids
  }

  output "public_az_subnet_ids" {
    value = module.public_subnets.az_subnet_ids
  }
  ```

  the output Maps of AZ names to subnet IDs look like these

  ```hcl
  public_az_subnet_ids = {
    us-east-2a = subnet-ea58d78e
    us-east-2b = subnet-556ee131
    us-east-2c = subnet-6f54db0b
  }
  private_az_subnet_ids = {
    us-east-2a = subnet-376de253
    us-east-2b = subnet-9e53dcfa
    us-east-2c = subnet-a86fe0cc
  }
  ```

  and the created subnet IDs could be found by the AZ names using `map["key"]` or [`lookup(map, key, [default])`](https://www.terraform.io/docs/configuration/interpolation.html#lookup-map-key-default-),

  for example:

  `public_az_subnet_ids["us-east-2a"]`

  `lookup(private_az_subnet_ids, "us-east-2b")`
  <br/>
screenshots:
  - name: "terraform-aws-multi-az-subnets"
    description: "Example of `terraform apply` outputs"
    url: "images/terraform-aws-multi-az-subnets.png"
include:
  - "docs/targets.md"
  - "docs/terraform.md"
# Contributors to this project
contributors: []