terraform-aws-multi-az-subnets

Terraform module for multi-AZ subnets 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.

This project is part of our comprehensive "SweetOps" approach towards DevOps.

It's 100% Open Source and licensed under the APACHE2.

Screenshots

Example of terraform apply outputs

Usage

locals {
  public_cidr_block  = cidrsubnet(var.cidr_block, 1, 0)
  private_cidr_block = cidrsubnet(var.cidr_block, 1, 1)
}

module "vpc" {
  source     = "git::https://github.com/cloudposse/terraform-aws-vpc.git?ref=master"
  namespace  = var.namespace
  stage      = var.stage
  name       = var.name
  cidr_block = var.cidr_block
}

module "public_subnets" {
  source              = "git::https://github.com/cloudposse/terraform-aws-multi-az-subnets.git?ref=master"
  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             = "git::https://github.com/cloudposse/terraform-aws-multi-az-subnets.git?ref=master"
  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

module "vpc" {
  source     = "git::https://github.com/cloudposse/terraform-aws-vpc.git?ref=master"
  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              = "git::https://github.com/cloudposse/terraform-aws-multi-az-subnets.git?ref=master"
  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              = "git::https://github.com/cloudposse/terraform-aws-multi-az-subnets.git?ref=master"
  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

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]),

for example:

public_az_subnet_ids["us-east-2a"]

lookup(private_az_subnet_ids, "us-east-2b")

Makefile Targets

Available targets:

  help                                Help screen
  help/all                            Display help for all targets
  help/short                          This help short screen
  lint                                Lint terraform code

Inputs

Name	Description	Type	Default	Required
attributes	Additional attributes (e.g. `policy` or `role`)	list(string)	`<list>`	no
availability_zones	List of Availability Zones (e.g. `['us-east-1a', 'us-east-1b', 'us-east-1c']`)	list(string)	-	yes
az_ngw_ids	Only for private subnets. Map of AZ names to NAT Gateway IDs that are used as default routes when creating private subnets	map(string)	`<map>`	no
cidr_block	Base CIDR block which is divided into subnet CIDR blocks (e.g. `10.0.0.0/16`)	string	-	yes
delimiter	Delimiter to be used between `namespace`, `stage`, `name` and `attributes`	string	`-`	no
enabled	Set to false to prevent the module from creating any resources	string	`true`	no
igw_id	Internet Gateway ID that is used as a default route when creating public subnets (e.g. `igw-9c26a123`)	string	``	no
max_subnets	Maximum number of subnets that can be created. The variable is used for CIDR blocks calculation	string	`6`	no
name	Application or solution name	string	-	yes
namespace	Namespace (e.g. `cp` or `cloudposse`)	string	-	yes
nat_gateway_enabled	Flag to enable/disable NAT Gateways creation in public subnets	string	`true`	no
private_network_acl_egress	Egress network ACL rules	list(map(string))	`<list>`	no
private_network_acl_id	Network ACL ID that is added to the private subnets. If empty, a new ACL will be created	string	``	no
private_network_acl_ingress	Egress network ACL rules	list(map(string))	`<list>`	no
public_network_acl_egress	Egress network ACL rules	list(map(string))	`<list>`	no
public_network_acl_id	Network ACL ID that is added to the public subnets. If empty, a new ACL will be created	string	``	no
public_network_acl_ingress	Egress network ACL rules	list(map(string))	`<list>`	no
stage	Stage (e.g. `prod`, `dev`, `staging`)	string	-	yes
tags	Additional tags (e.g. map(`BusinessUnit`,`XYZ`)	map(string)	`<map>`	no
type	Type of subnets to create (`private` or `public`)	string	`private`	no
vpc_id	VPC ID	string	-	yes

Outputs

Name	Description
az_ngw_ids	Map of AZ names to NAT Gateway IDs (only for public subnets)
az_route_table_ids	Map of AZ names to Route Table IDs
az_subnet_arns	Map of AZ names to subnet ARNs
az_subnet_ids	Map of AZ names to subnet IDs

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Related Projects

Check out these related projects.

terraform-aws-named-subnets - Terraform module for named subnets provisioning.
terraform-aws-dynamic-subnets - Terraform module for public and private subnets provisioning in existing VPC
terraform-aws-vpc - Terraform Module that defines a VPC with public/private subnets across multiple AZs with Internet Gateways
terraform-aws-cloudwatch-flow-logs - Terraform module for enabling flow logs for vpc and subnets.

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Copyright

License

See LICENSE for full details.

Licensed to the Apache Software Foundation (ASF) under one
or more contributor license agreements.  See the NOTICE file
distributed with this work for additional information
regarding copyright ownership.  The ASF licenses this file
to you under the Apache License, Version 2.0 (the
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Contributors

Andriy Knysh	Maxim Mironenko

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