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DEPRECATED (use cloudposse/terraform-aws-dynamic-subnets instead): Terraform module for multi-AZ public and private subnets provisioning

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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.

Screenshots

terraform-aws-multi-az-subnetsExample of terraform apply outputs

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Usage

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
}

Important

In Cloud Posse's examples, we avoid pinning modules to specific versions to prevent discrepancies between the documentation and the latest released versions. However, for your own projects, we strongly advise pinning each module to the exact version you're using. This practice ensures the stability of your infrastructure. Additionally, we recommend implementing a systematic approach for updating versions to avoid unexpected changes.

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")

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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 >= 3.0
local >= 1.2
null >= 2.0

Providers

Name Version
aws >= 3.0

Modules

Name Source Version
private_label cloudposse/label/null 0.24.1
public_label cloudposse/label/null 0.24.1
this cloudposse/label/null 0.25.0

Resources

Name Type
aws_eip.public resource
aws_nat_gateway.public resource
aws_network_acl.private resource
aws_network_acl.public resource
aws_route.default resource
aws_route.public resource
aws_route.public_ipv6 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

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_zones List of Availability Zones (e.g. ['us-east-1a', 'us-east-1b', 'us-east-1c']) list(string) n/a 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.
You should either supply one NAT Gateway ID for each AZ in var.availability_zones or leave the map empty.
If empty, no default egress route will be created and you will have to create your own using aws_route.
map(string) {} no
cidr_block Base CIDR block which is 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
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 that is used as a default route when creating public subnets (e.g. igw-9c26a123) string "" no
ipv6_cidr_block Base IPv6 CIDR block which is divided into /64 subnet CIDR blocks string null no
ipv6_enabled Flag to enable/disable IPv6 creation in public subnets bool false 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
max_subnets Maximum number of subnets that can be created. The variable is used for CIDR blocks calculation string "6" 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_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))
[
{
"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 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))
[
{
"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 Egress network ACL rules list(map(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 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))
[
{
"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
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 to create (private or public) string "private" no
vpc_id VPC ID string n/a 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_cidr_blocks Map of AZ names to subnet CIDR blocks
az_subnet_ids Map of AZ names to subnet IDs
az_subnet_ipv6_cidr_blocks Map of AZ names to subnet IPv6 CIDR blocks
az_subnet_map Map of AZ names to map of information about subnets

Related Projects

Check out these related projects.

✨ Contributing

This project is under active development, and we encourage contributions from our community.

Many thanks to our outstanding contributors:

For πŸ› bug reports & feature requests, please use the issue tracker.

In general, PRs are welcome. We follow the typical "fork-and-pull" Git workflow.

  1. Review our Code of Conduct and Contributor Guidelines.
  2. Fork the repo on GitHub
  3. Clone the project to your own machine
  4. Commit changes to your own branch
  5. Push your work back up to your fork
  6. Submit a Pull Request so that we can review your changes

NOTE: Be sure to merge the latest changes from "upstream" before making a pull request!

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License

License

Preamble to the Apache License, Version 2.0

Complete license is available in the LICENSE file.

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.

Trademarks

All other trademarks referenced herein are the property of their respective owners.


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