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DEPRECATED (use cloudposse/terraform-aws-dynamic-subnets instead): Terraform module for named subnets provisioning.

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Cloud Posse

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Terraform module for named subnets provisioning.


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

Terraform Open Source Modules

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Usage

IMPORTANT: The master branch is used in source just as an example. In your code, do not pin to master because there may be breaking changes between releases. Instead pin to the release tag (e.g. ?ref=tags/x.y.z) of one of our latest releases.

Simple example, with private and public subnets in one Availability Zone:

module "vpc" {
  source     = "git::https://github.com/cloudposse/terraform-aws-vpc.git?ref=master"
  namespace  = "eg"
  name       = "vpc"
  stage      = "dev"
  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-named-subnets.git?ref=master"
  namespace         = "eg"
  stage             = "dev"
  name              = "app"
  subnet_names      = ["web1", "web2", "web3"]
  vpc_id            = module.vpc.vpc_id
  cidr_block        = local.public_cidr_block
  type              = "public"
  igw_id            = module.vpc.igw_id
  availability_zone = "us-east-1a"
}

module "private_subnets" {
  source            = "git::https://github.com/cloudposse/terraform-aws-named-subnets.git?ref=master"
  namespace         = "eg"
  stage             = "dev"
  name              = "database"
  subnet_names      = ["kafka", "cassandra", "zookeeper"]
  vpc_id            = module.vpc.vpc_id
  cidr_block        = local.private_cidr_block
  type              = "private"
  availability_zone = "us-east-1a"
  ngw_id            = module.public_subnets.ngw_id
}

Simple example, with ENI as default route gateway for private subnets

resource "aws_network_interface" "default" {
  subnet_id         = module.us_east_1b_public_subnets.subnet_ids[0]
  source_dest_check = false
  tags              = module.network_interface_label.id
}

module "us_east_1b_private_subnets" {
  source            = "git::https://github.com/cloudposse/terraform-aws-named-subnets.git?ref=master"
  namespace         = "eg"
  stage             = "dev"
  name              = "app"
  subnet_names      = ["charlie", "echo", "bravo"]
  vpc_id            = module.vpc.vpc_id
  cidr_block        = local.us_east_1b_private_cidr_block
  type              = "private"
  availability_zone = "us-east-1b"
  eni_id            = aws_network_interface.default.id
  attributes        = ["us-east-1b"]
}

Full example, with private and public subnets in two Availability Zones for High Availability:

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

locals {
  us_east_1a_public_cidr_block  = cidrsubnet(module.vpc.vpc_cidr_block, 2, 0)
  us_east_1a_private_cidr_block = cidrsubnet(module.vpc.vpc_cidr_block, 2, 1)
  us_east_1b_public_cidr_block  = cidrsubnet(module.vpc.vpc_cidr_block, 2, 2)
  us_east_1b_private_cidr_block = cidrsubnet(module.vpc.vpc_cidr_block, 2, 3)
}

module "us_east_1a_public_subnets" {
  source            = "git::https://github.com/cloudposse/terraform-aws-named-subnets.git?ref=master"
  namespace         = "eg"
  stage             = "dev"
  name              = "app"
  subnet_names      = ["apples", "oranges", "grapes"]
  vpc_id            = module.vpc.vpc_id
  cidr_block        = local.us_east_1a_public_cidr_block
  type              = "public"
  igw_id            = module.vpc.igw_id
  availability_zone = "us-east-1a"
  attributes        = ["us-east-1a"]
}

module "us_east_1a_private_subnets" {
  source            = "git::https://github.com/cloudposse/terraform-aws-named-subnets.git?ref=master"
  namespace         = "eg"
  stage             = "dev"
  name              = "app"
  subnet_names      = ["charlie", "echo", "bravo"]
  vpc_id            = module.vpc.vpc_id
  cidr_block        = local.us_east_1a_private_cidr_block
  type              = "private"
  availability_zone = "us-east-1a"
  ngw_id            = module.us_east_1a_public_subnets.ngw_id
  attributes        = ["us-east-1a"]
}

module "us_east_1b_public_subnets" {
  source            = "git::https://github.com/cloudposse/terraform-aws-named-subnets.git?ref=master"
  namespace         = "eg"
  stage             = "dev"
  name              = "app"
  subnet_names      = ["apples", "oranges", "grapes"]
  vpc_id            = module.vpc.vpc_id
  cidr_block        = local.us_east_1b_public_cidr_block
  type              = "public"
  igw_id            = module.vpc.igw_id
  availability_zone = "us-east-1b"
  attributes        = ["us-east-1b"]
}

module "us_east_1b_private_subnets" {
  source            = "git::https://github.com/cloudposse/terraform-aws-named-subnets.git?ref=master"
  namespace         = "eg"
  stage             = "dev"
  name              = "app"
  subnet_names      = ["charlie", "echo", "bravo"]
  vpc_id            = module.vpc.vpc_id
  cidr_block        = local.us_east_1b_private_cidr_block
  type              = "private"
  availability_zone = "us-east-1b"
  ngw_id            = module.us_east_1b_public_subnets.ngw_id
  attributes        = ["us-east-1b"]
}

resource "aws_network_interface" "default" {
  subnet_id         = module.us_east_1b_public_subnets.subnet_ids[0]
  source_dest_check = false
  tags              = module.network_interface_label.id
}

module "us_east_1b_private_subnets" {
  source            = "git::https://github.com/cloudposse/terraform-aws-named-subnets.git?ref=master"
  namespace         = "eg"
  stage             = "dev"
  name              = "app"
  subnet_names      = ["charlie", "echo", "bravo"]
  vpc_id            = module.vpc.vpc_id
  cidr_block        = local.us_east_1b_private_cidr_block
  type              = "private"
  availability_zone = "us-east-1b"
  eni_id            = aws_network_interface.default.id
  attributes        = ["us-east-1b"]
}

Caveat

You must use only one type of device for a default route gateway per route table. ENI or NGW

Given the following configuration (see the Simple example above)

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

module "public_subnets" {
  source            = "git::https://github.com/cloudposse/terraform-aws-named-subnets.git?ref=master"
  namespace         = "eg"
  stage             = "dev"
  name              = "app"
  subnet_names      = ["web1", "web2", "web3"]
  vpc_id            = var.vpc_id
  cidr_block        = local.public_cidr_block
  type              = "public"
  availability_zone = "us-east-1a"
  igw_id            = var.igw_id
}

module "private_subnets" {
  source            = "git::https://github.com/cloudposse/terraform-aws-named-subnets.git?ref=master"
  namespace         = "eg"
  stage             = "dev"
  name              = "database"
  subnet_names      = ["kafka", "cassandra", "zookeeper"]
  vpc_id            = var.vpc_id
  cidr_block        = local.private_cidr_block
  type              = "private"
  availability_zone = "us-east-1a"
  ngw_id            = module.public_subnets.ngw_id
}

output "private_named_subnet_ids" {
  value = module.private_subnets.named_subnet_ids
}

output "public_named_subnet_ids" {
  value = module.public_subnets.named_subnet_ids
}

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

public_named_subnet_ids = {
  web1 = subnet-ea58d78e
  web2 = subnet-556ee131
  web3 = subnet-6f54db0b
}
private_named_subnet_ids = {
  cassandra = subnet-376de253
  kafka = subnet-9e53dcfa
  zookeeper = subnet-a86fe0cc
}

and the created subnet IDs could be found by the subnet names using map["key"] or lookup(map, key, [default]),

for example:

public_named_subnet_ids["web1"]

lookup(private_named_subnet_ids, "kafka")

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_zone Availability Zone string - yes
cidr_block Base CIDR block which will be divided into subnet CIDR blocks (e.g. 10.0.0.0/16) string - yes
delimiter Delimiter to be used between name, namespace, stage, attributes string - no
enabled Set to false to prevent the module from creating any resources bool true no
eni_id An ID of a network interface which is used as a default route in private route tables (e.g. eni-9c26a123) string `` no
igw_id Internet Gateway ID which will be used as a default route in public route tables (e.g. igw-9c26a123). Conflicts with ngw_id string `` no
max_subnets Maximum number of subnets which can be created. This variable is being used for CIDR blocks calculation. Defaults to length of subnet_names argument number 16 no
name Application or solution name string - yes
namespace Namespace (e.g. eg or cp) string `` no
nat_enabled Enable/disable NAT Gateway bool true no
ngw_id NAT Gateway ID which will be used as a default route in private route tables (e.g. igw-9c26a123). Conflicts with igw_id string `` no
private_network_acl_egress Private network egress ACL rules object <list> no
private_network_acl_id Network ACL ID that will be added to the subnets. If empty, a new ACL will be created string `` no
private_network_acl_ingress Private network ingress ACL rules object <list> no
public_network_acl_egress Public network egress ACL rules object <list> no
public_network_acl_id Network ACL ID that will be added to the subnets. If empty, a new ACL will be created string `` no
public_network_acl_ingress Public network ingress ACL rules object <list> no
stage Stage (e.g. prod, dev, staging) string `` no
subnet_names List of subnet names (e.g. ['apples', 'oranges', 'grapes']) list(string) - yes
tags Additional tags (e.g. map(BusinessUnit,XYZ) map(string) <map> no
type Type of subnets (private or public) string private no
vpc_id VPC ID string - yes

Outputs

Name Description
named_subnet_ids Map of subnet names to subnet IDs
ngw_id NAT Gateway ID
ngw_private_ip Private IP address of the NAT Gateway
ngw_public_ip Public IP address of the NAT Gateway
route_table_ids Route table IDs
subnet_ids Subnet IDs

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Copyright

Copyright © 2017-2020 Cloud Posse, LLC

License

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

Erik Osterman
Erik Osterman
Andriy Knysh
Andriy Knysh
Sergey Vasilyev
Sergey Vasilyev
Vladimir
Vladimir
Konstantin B
Konstantin B

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