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.
This project is part of our comprehensive "SweetOps" approach towards DevOps.
It's 100% Open Source and licensed under the APACHE2.
Example of terraform apply outputs
module "vpc" {
source = "git::https://github.com/cloudposse/terraform-aws-vpc.git?ref=master"
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 = "${cidrsubnet(module.vpc.vpc_cidr_block, 1, 1)}"
}
module "public_subnets" {
source = "git::https://github.com/cloudposse/terraform-aws-multi-az-subnets.git?ref=master"
namespace = "${var.namespace}"
stage = "${var.stage}"
name = "${var.name}"
availability_zones = ["us-east-1a", "us-east-1b", "us-east-1c"]
vpc_id = "${module.vpc.vpc_id}"
cidr_block = "${local.public_cidr_block}"
type = "public"
igw_id = "${module.vpc.igw_id}"
nat_gateway_enabled = "true"
}
module "private_subnets" {
source = "git::https://github.com/cloudposse/terraform-aws-multi-az-subnets.git?ref=master"
namespace = "${var.namespace}"
stage = "${var.stage}"
name = "${var.name}"
availability_zones = ["us-east-1a", "us-east-1b", "us-east-1c"]
vpc_id = "${module.vpc.vpc_id}"
cidr_block = "${local.private_cidr_block}"
type = "private"
# Map of AZ names to NAT Gateway IDs that was created in "public_subnets" module
az_ngw_ids = "${module.public_subnets.az_ngw_ids}"
# Need to explicitly provide the count since Terraform currently can't use dynamic count on computed resources from different modules
# https://github.com/hashicorp/terraform/issues/10857
# https://github.com/hashicorp/terraform/issues/12125
# https://github.com/hashicorp/terraform/issues/4149
az_ngw_count = 3
}Given the following configuration
module "vpc" {
source = "git::https://github.com/cloudposse/terraform-aws-vpc.git?ref=master"
namespace = "${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 = "git::https://github.com/cloudposse/terraform-aws-multi-az-subnets.git?ref=master"
namespace = "${var.namespace}"
stage = "${var.stage}"
name = "${var.name}"
availability_zones = ["us-east-1a", "us-east-1b", "us-east-1c"]
vpc_id = "${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 = "git::https://github.com/cloudposse/terraform-aws-multi-az-subnets.git?ref=master"
namespace = "${var.namespace}"
stage = "${var.stage}"
name = "${var.name}"
availability_zones = ["us-east-1a", "us-east-1b", "us-east-1c"]
vpc_id = "${module.vpc.vpc_id}"
cidr_block = "${local.private_cidr_block}"
type = "private"
az_ngw_ids = "${module.public_subnets.az_ngw_ids}"
az_ngw_count = 3
}
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-1a = subnet-ea58d78e
us-east-1b = subnet-556ee131
us-east-1c = subnet-6f54db0b
}
private_az_subnet_ids = {
us-east-1a = subnet-376de253
us-east-1b = subnet-9e53dcfa
us-east-1c = 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-1a"]
lookup(private_az_subnet_ids, "us-east-1b")
Available targets:
help Help screen
help/all Display help for all targets
help/short This help short screen
lint Lint terraform code
| Name | Description | Type | Default | Required |
|---|---|---|---|---|
| attributes | Additional attributes (e.g. policy or role) |
list | <list> |
no |
| availability_zones | List of Availability Zones (e.g. ['us-east-1a', 'us-east-1b', 'us-east-1c']) |
list | <list> |
no |
| az_ngw_count | Count of items in the az_ngw_ids map. Needs to be explicitly provided since Terraform currently can't use dynamic count on computed resources from different modules. hashicorp/terraform#10857 |
string | 0 |
no |
| 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 | map | <map> |
no |
| cidr_block | Base CIDR block which is divided into subnet CIDR blocks (e.g. 10.0.0.0/16) |
string | - | yes |
| delimiter | Delimiter to be used between namespace, stage, name and attributes |
string | - |
no |
| enabled | Set to false to prevent the module from creating any resources | string | true |
no |
| igw_id | Internet Gateway ID that is used as a default route when creating public subnets (e.g. igw-9c26a123) |
string | `` | no |
| max_subnets | Maximum number of subnets that can be created. The variable is used for CIDR blocks calculation | string | 6 |
no |
| name | Application or solution name | string | - | yes |
| namespace | Namespace (e.g. cp or cloudposse) |
string | - | yes |
| 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 | <list> |
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 | <list> |
no |
| public_network_acl_egress | Egress network ACL rules | list | <list> |
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 | <list> |
no |
| stage | Stage (e.g. prod, dev, staging) |
string | - | yes |
| tags | Additional tags (e.g. map(BusinessUnit,XYZ) |
map | <map> |
no |
| type | Type of subnets to create (private or public) |
string | private |
no |
| vpc_id | VPC ID | string | - | yes |
| 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_ids | Map of AZ names to subnet IDs |
Check out these related projects.
- terraform-aws-named-subnets - Terraform module for named 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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