Terraform module for named subnets
provisioning.
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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"]
}
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")
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.
Available targets:
help Help screen
help/all Display help for all targets
help/short This help short screen
lint Lint terraform code
Name | Version |
---|---|
terraform | >= 0.13.0 |
aws | >= 2.0 |
null | >= 2.0 |
Name | Version |
---|---|
aws | >= 2.0 |
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 |
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 |
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 |
{ |
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 beidentical 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 bechanged in later chained modules. Attempts to change it will be silently ignored. |
set(string) |
[ |
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( |
[ |
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( |
[ |
no |
public_network_acl_egress | Public network egress ACL rules | list(object( |
[ |
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( |
[ |
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 |
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 |
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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