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.

If you are creating subnets inside a VPC, consider using cloudposse/terraform-aws-dynamic-subnets instead.

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

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

We literally have hundreds of terraform modules that are Open Source and well-maintained. Check them out!

Screenshots

Example of terraform apply outputs

Security & Compliance

Security scanning is graciously provided by Bridgecrew. Bridgecrew is the leading fully hosted, cloud-native solution providing continuous Terraform security and compliance.

Benchmark	Description
	Infrastructure Security Compliance
	Center for Internet Security, KUBERNETES Compliance
	Center for Internet Security, AWS Compliance
	Center for Internet Security, AZURE Compliance
	Payment Card Industry Data Security Standards Compliance
	National Institute of Standards and Technology Compliance
	Information Security Management System, ISO/IEC 27001 Compliance
	Service Organization Control 2 Compliance
	Center for Internet Security, GCP Compliance
	Health Insurance Portability and Accountability Compliance

Usage

IMPORTANT: We do not pin modules to versions in our examples because of the difficulty of keeping the versions in the documentation in sync with the latest released versions. We highly recommend that in your code you pin the version to the exact version you are using so that your infrastructure remains stable, and update versions in a systematic way so that they do not catch you by surprise.

Also, because of a bug in the Terraform registry (hashicorp/terraform#21417), the registry shows many of our inputs as required when in fact they are optional. The table below correctly indicates which inputs are required.

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

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

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

Requirements

Providers

Inputs

{
  "additional_tag_map": {},
  "attributes": [],
  "delimiter": null,
  "enabled": true,
  "environment": null,
  "id_length_limit": null,
  "label_key_case": null,
  "label_order": [],
  "label_value_case": null,
  "name": null,
  "namespace": null,
  "regex_replace_chars": null,
  "stage": null,
  "tags": {}
}

[
  {
    "action": "allow",
    "cidr_block": "0.0.0.0/0",
    "from_port": 0,
    "protocol": "-1",
    "rule_no": 100,
    "to_port": 0
  }
]

[
  {
    "action": "allow",
    "cidr_block": "0.0.0.0/0",
    "from_port": 0,
    "protocol": "-1",
    "rule_no": 100,
    "to_port": 0
  }
]

[
  {
    "action": "allow",
    "cidr_block": "0.0.0.0/0",
    "from_port": 0,
    "protocol": "-1",
    "rule_no": 100,
    "to_port": 0
  }
]

[
  {
    "action": "allow",
    "cidr_block": "0.0.0.0/0",
    "from_port": 0,
    "protocol": "-1",
    "rule_no": 100,
    "to_port": 0
  }
]

Outputs

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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.

Help

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File a GitHub issue, send us an email or join our Slack Community.

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Copyright

Copyright © 2017-2021 Cloud Posse, LLC

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
"License"); you may not use this file except in compliance
with the License.  You may obtain a copy of the License at

  https://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing,
software distributed under the License is distributed on an
"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
KIND, either express or implied.  See the License for the
specific language governing permissions and limitations
under the License.

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Contributors

Andriy Knysh	Maxim Mironenko