Module: `named-subnets`

Terraform module for named subnets provisioning.

Usage

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")

Variables

Required Variables

availability_zone (string) required: Availability Zone
cidr_block (string) required: Base CIDR block which will be divided into subnet CIDR blocks (e.g. 10.0.0.0/16)
subnet_names (list(string)) required: List of subnet names (e.g. ['apples', 'oranges', 'grapes'])
vpc_id (string) required: VPC ID

Optional Variables

eni_id (string) optional

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.

Default value: ""

igw_id (string) optional

Internet Gateway ID which will be used as a default route in public route tables (e.g. igw-9c26a123).

Default value: ""

map_public_ip_on_launch_enabled (bool) optional

Enable/disable map_public_ip_on_launch subnet attribute.

Default value: false

max_subnets (number) optional

Maximum number of subnets which can be created. This variable is being used for CIDR blocks calculation. Defaults to length of subnet_names argument

Default value: 16

nat_enabled (bool) optional

Enable/disable NAT Gateway

Default value: true

ngw_id (string) optional

NAT Gateway ID which will be used as a default route in private route tables (e.g. igw-9c26a123). Conflicts with eni_id.

Default value: ""

private_network_acl_egress optional

Private network egress ACL rules

Type:

list(object(
{
  rule_no    = number
  action     = string
  cidr_block = string
  from_port  = number
  to_port    = number
  protocol   = string
}))

Default value:

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

private_network_acl_id (string) optional

Network ACL ID that will be added to the subnets. If empty, a new ACL will be created

Default value: ""

private_network_acl_ingress optional

Private network ingress ACL rules

Type:

list(object(
{
  rule_no    = number
  action     = string
  cidr_block = string
  from_port  = number
  to_port    = number
  protocol   = string
}))

Default value:

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

public_network_acl_egress optional

Public network egress ACL rules

Type:

list(object(
{
  rule_no    = number
  action     = string
  cidr_block = string
  from_port  = number
  to_port    = number
  protocol   = string
}))

Default value:

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

public_network_acl_id (string) optional

Network ACL ID that will be added to the subnets. If empty, a new ACL will be created

Default value: ""

public_network_acl_ingress optional

Public network ingress ACL rules

Type:

list(object(
{
  rule_no    = number
  action     = string
  cidr_block = string
  from_port  = number
  to_port    = number
  protocol   = string
}))

Default value:

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

type (string) optional

Type of subnets (private or public)

Default value: "private"

Context Variables

The following variables are defined in the context.tf file of this module and part of the terraform-null-label pattern.

additional_tag_map (map(string)) optional

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.

Required: No

Default value: { }

attributes (list(string)) optional

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.

Required: No

Default value: [ ]

context (any) optional

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.

Required: No

Default value:

{
  "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
}

delimiter (string) optional

Delimiter to be used between ID elements.
Defaults to - (hyphen). Set to "" to use no delimiter at all.

Required: No

Default value: null

descriptor_formats (any) optional

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).

Required: No

Default value: { }

enabled (bool) optional

Set to false to prevent the module from creating any resources
Required: No

Default value: null

environment (string) optional

ID element. Usually used for region e.g. 'uw2', 'us-west-2', OR role 'prod', 'staging', 'dev', 'UAT'
Required: No

Default value: null

id_length_limit (number) optional

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.

Required: No

Default value: null

label_key_case (string) optional

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.

Required: No

Default value: null

label_order (list(string)) optional

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.

Required: No

Default value: null

label_value_case (string) optional

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.

Required: No

Default value: null

labels_as_tags (set(string)) optional

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.

Required: No

Default value:

[
  "default"
]

name (string) optional

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.

Required: No

Default value: null

namespace (string) optional

ID element. Usually an abbreviation of your organization name, e.g. 'eg' or 'cp', to help ensure generated IDs are globally unique
Required: No

Default value: null

regex_replace_chars (string) optional

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.

Required: No

Default value: null

stage (string) optional

ID element. Usually used to indicate role, e.g. 'prod', 'staging', 'source', 'build', 'test', 'deploy', 'release'
Required: No

Default value: null

tags (map(string)) optional

Additional tags (e.g. {'BusinessUnit': 'XYZ'}).
Neither the tag keys nor the tag values will be modified by this module.

Required: No

Default value: { }

tenant (string) optional

ID element (Rarely used, not included by default). A customer identifier, indicating who this instance of a resource is for
Required: No

Default value: null

Outputs

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

Dependencies

Requirements

terraform, version: >= 0.13.0
aws, version: >= 2.0
null, version: >= 2.0

Providers

aws, version: >= 2.0

Modules

Name	Version	Source	Description
`private_label`	0.25.0	`cloudposse/label/null`	n/a
`public_label`	0.25.0	`cloudposse/label/null`	n/a
`this`	0.25.0	`cloudposse/label/null`	n/a

Resources

The following resources are used by this module:

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)

Data Sources

The following data sources are used by this module:

aws_vpc.default (data source)

Module: named-subnets

Usage​

Caveat​

Variables​

Required Variables​

Optional Variables​

Context Variables​

Outputs​

Dependencies​

Requirements​

Providers​

Modules​

Resources​

Data Sources​

Module: `named-subnets`

Usage

Caveat

Variables

Required Variables

Optional Variables

Context Variables

Outputs

Dependencies

Requirements

Providers

Modules

Resources

Data Sources