terraform-aws-named-subnets

Terraform module for named subnets provisioning.

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

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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.

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

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

Requirements

Name	Version
terraform	>= 0.13.0
aws	>= 2.0
null	>= 2.0

Providers

Name	Version
aws	>= 2.0

Modules

Name	Source	Version
private_label	cloudposse/label/null	0.25.0
public_label	cloudposse/label/null	0.25.0
this	cloudposse/label/null	0.25.0

Resources

Name	Type
aws_eip.default	resource
aws_nat_gateway.default	resource
aws_network_acl.private	resource
aws_network_acl.public	resource
aws_route.private	resource
aws_route.public	resource
aws_route_table.private	resource
aws_route_table.public	resource
aws_route_table_association.private	resource
aws_route_table_association.public	resource
aws_subnet.private	resource
aws_subnet.public	resource
aws_vpc.default	data source

Inputs

Name	Description	Type	Default	Required
additional_tag_map	Additional key-value pairs to add to each map in tags_as_list_of_maps. Not added to tags or id. This is for some rare cases where resources want additional configuration of tags and therefore take a list of maps with tag key, value, and additional configuration.	map(string)	{}	no
attributes	ID element. Additional attributes (e.g. workers or cluster) to add to id, in the order they appear in the list. New attributes are appended to the end of the list. The elements of the list are joined by the delimiter and treated as a single ID element.	list(string)	[]	no
availability_zone	Availability Zone	string	n/a	yes
cidr_block	Base CIDR block which will be divided into subnet CIDR blocks (e.g. 10.0.0.0/16)	string	n/a	yes
context	Single object for setting entire context at once. See description of individual variables for details. Leave string and numeric variables as null to use default value. Individual variable settings (non-null) override settings in context object, except for attributes, tags, and additional_tag_map, which are merged.	any	{ "additional_tag_map": {}, "attributes": [], "delimiter": null, "descriptor_formats": {}, "enabled": true, "environment": null, "id_length_limit": null, "label_key_case": null, "label_order": [], "label_value_case": null, "labels_as_tags": [ "unset" ], "name": null, "namespace": null, "regex_replace_chars": null, "stage": null, "tags": {}, "tenant": null }	no
delimiter	Delimiter to be used between ID elements. Defaults to - (hyphen). Set to "" to use no delimiter at all.	string	null	no
descriptor_formats	Describe additional descriptors to be output in the descriptors output map. Map of maps. Keys are names of descriptors. Values are maps of the form {<br> format = string<br> labels = list(string)<br>} (Type is any so the map values can later be enhanced to provide additional options.) format is a Terraform format string to be passed to the format() function. labels is a list of labels, in order, to pass to format() function. Label values will be normalized before being passed to format() so they will be identical to how they appear in id. Default is {} (descriptors output will be empty).	any	{}	no
enabled	Set to false to prevent the module from creating any resources	bool	null	no
eni_id	An ID of a network interface which is used as a default route in private route tables (_e.g._ eni-9c26a123). Conflicts with ngw_id.	string	""	no
environment	ID element. Usually used for region e.g. 'uw2', 'us-west-2', OR role 'prod', 'staging', 'dev', 'UAT'	string	null	no
id_length_limit	Limit id to this many characters (minimum 6). Set to 0 for unlimited length. Set to null for keep the existing setting, which defaults to 0. Does not affect id_full.	number	null	no
igw_id	Internet Gateway ID which will be used as a default route in public route tables (e.g. igw-9c26a123).	string	""	no
label_key_case	Controls the letter case of the tags keys (label names) for tags generated by this module. Does not affect keys of tags passed in via the tags input. Possible values: lower, title, upper. Default value: title.	string	null	no
label_order	The order in which the labels (ID elements) appear in the id. Defaults to ["namespace", "environment", "stage", "name", "attributes"]. You can omit any of the 6 labels ("tenant" is the 6th), but at least one must be present.	list(string)	null	no
label_value_case	Controls the letter case of ID elements (labels) as included in id, set as tag values, and output by this module individually. Does not affect values of tags passed in via the tags input. Possible values: lower, title, upper and none (no transformation). Set this to title and set delimiter to "" to yield Pascal Case IDs. Default value: lower.	string	null	no
labels_as_tags	Set of labels (ID elements) to include as tags in the tags output. Default is to include all labels. Tags with empty values will not be included in the tags output. Set to [] to suppress all generated tags. Notes: The value of the name tag, if included, will be the id, not the name. Unlike other null-label inputs, the initial setting of labels_as_tags cannot be changed in later chained modules. Attempts to change it will be silently ignored.	set(string)	[ "default" ]	no
map_public_ip_on_launch_enabled	Enable/disable map_public_ip_on_launch subnet attribute.	bool	false	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	ID element. Usually the component or solution name, e.g. 'app' or 'jenkins'. This is the only ID element not also included as a tag. The "name" tag is set to the full id string. There is no tag with the value of the name input.	string	null	no
namespace	ID element. Usually an abbreviation of your organization name, e.g. 'eg' or 'cp', to help ensure generated IDs are globally unique	string	null	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 eni_id.	string	""	no
private_network_acl_egress	Private network egress ACL rules	list(object( { rule_no = number action = string cidr_block = string from_port = number to_port = number protocol = string }))	[ { "action": "allow", "cidr_block": "0.0.0.0/0", "from_port": 0, "protocol": "-1", "rule_no": 100, "to_port": 0 } ]	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	list(object( { rule_no = number action = string cidr_block = string from_port = number to_port = number protocol = string }))	[ { "action": "allow", "cidr_block": "0.0.0.0/0", "from_port": 0, "protocol": "-1", "rule_no": 100, "to_port": 0 } ]	no
public_network_acl_egress	Public network egress ACL rules	list(object( { rule_no = number action = string cidr_block = string from_port = number to_port = number protocol = string }))	[ { "action": "allow", "cidr_block": "0.0.0.0/0", "from_port": 0, "protocol": "-1", "rule_no": 100, "to_port": 0 } ]	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	list(object( { rule_no = number action = string cidr_block = string from_port = number to_port = number protocol = string }))	[ { "action": "allow", "cidr_block": "0.0.0.0/0", "from_port": 0, "protocol": "-1", "rule_no": 100, "to_port": 0 } ]	no
regex_replace_chars	Terraform regular expression (regex) string. Characters matching the regex will be removed from the ID elements. If not set, "/[^a-zA-Z0-9-]/" is used to remove all characters other than hyphens, letters and digits.	string	null	no
stage	ID element. Usually used to indicate role, e.g. 'prod', 'staging', 'source', 'build', 'test', 'deploy', 'release'	string	null	no
subnet_names	List of subnet names (e.g. ['apples', 'oranges', 'grapes'])	list(string)	n/a	yes
tags	Additional tags (e.g. {'BusinessUnit': 'XYZ'}). Neither the tag keys nor the tag values will be modified by this module.	map(string)	{}	no
tenant	ID element _(Rarely used, not included by default)_. A customer identifier, indicating who this instance of a resource is for	string	null	no
type	Type of subnets (private or public)	string	"private"	no
vpc_id	VPC ID	string	n/a	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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Related Projects

Check out these related projects.

• terraform-aws-multi-az-subnets - Terraform module for multi-AZ public and private 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

Copyright © 2017-2022 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
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Contributors

Erik Osterman	Andriy Knysh	Sergey Vasilyev	Vladimir	Konstantin B