{"id":14957942,"url":"https://github.com/cloudposse/terraform-aws-dynamic-subnets","last_synced_at":"2026-01-07T17:25:22.357Z","repository":{"id":37788762,"uuid":"99687248","full_name":"cloudposse/terraform-aws-dynamic-subnets","owner":"cloudposse","description":"Terraform module for public and private subnets provisioning in existing 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markdownlint-disable --\u003e\n\u003ca href=\"https://cpco.io/homepage\"\u003e\u003cimg src=\"https://github.com/cloudposse/terraform-aws-dynamic-subnets/blob/main/.github/banner.png?raw=true\" alt=\"Project Banner\"/\u003e\u003c/a\u003e\u003cbr/\u003e\n\n\n\u003cp align=\"right\"\u003e\u003ca href=\"https://github.com/cloudposse/terraform-aws-dynamic-subnets/releases/latest\"\u003e\u003cimg src=\"https://img.shields.io/github/release/cloudposse/terraform-aws-dynamic-subnets.svg?style=for-the-badge\" alt=\"Latest Release\"/\u003e\u003c/a\u003e\u003ca href=\"https://github.com/cloudposse/terraform-aws-dynamic-subnets/commits\"\u003e\u003cimg src=\"https://img.shields.io/github/last-commit/cloudposse/terraform-aws-dynamic-subnets.svg?style=for-the-badge\" alt=\"Last Updated\"/\u003e\u003c/a\u003e\u003ca href=\"https://cloudposse.com/slack\"\u003e\u003cimg src=\"https://slack.cloudposse.com/for-the-badge.svg\" alt=\"Slack Community\"/\u003e\u003c/a\u003e\u003ca href=\"https://cloudposse.com/support/\"\u003e\u003cimg src=\"https://img.shields.io/badge/Get_Support-success.svg?style=for-the-badge\" alt=\"Get Support\"/\u003e\u003c/a\u003e\n\n\u003c/p\u003e\n\u003c!-- markdownlint-restore --\u003e\n\n\u003c!--\n\n\n\n\n  ** DO NOT EDIT THIS FILE\n  **\n  ** This file was automatically generated by the `cloudposse/build-harness`.\n  ** 1) Make all changes to `README.yaml`\n  ** 2) Install [atmos](https://atmos.tools/install/) (you only need to do this once)\n  ** 3) Run`atmos readme` to rebuild this file.\n  **\n  ** (We maintain HUNDREDS of open source projects. This is how we maintain our sanity.)\n  **\n\n\n\n\n\n--\u003e\n\nTerraform module to provision public and private [`subnets`](https://docs.aws.amazon.com/AmazonVPC/latest/UserGuide/VPC_Subnets.html) in an existing [`VPC`](https://aws.amazon.com/vpc)\n\n\n__Note:__ This module is intended for use with an existing VPC and existing Internet Gateway.\nTo create a new VPC, use [terraform-aws-vpc](https://github.com/cloudposse/terraform-aws-vpc) module.\n\n__Note:__ Due to Terraform [limitations](https://github.com/hashicorp/terraform/issues/26755#issuecomment-719103775),\nmany optional inputs to this module are specified as a `list(string)` that can have zero or one element, rather than\nas a `string` that could be empty or `null`. The designation of an input as a `list` type does not necessarily\nmean that you can supply more than one value in the list, so check the input's description before supplying more than one value.\n\nThe core function of this module is to create 2 sets of subnets, a \"public\" set with bidirectional access to the\npublic internet, and a \"private\" set behind a firewall with egress-only access to the public internet. This\nincludes dividing up a given CIDR range so that a each subnet gets its own\ndistinct CIDR range within that range, and then creating those subnets in the appropriate availability zones.\nThe intention is to keep this module relatively simple and easy to use for the most popular use cases.\nIn its default configuration, this module creates 1 public subnet and 1 private subnet in each\nof the specified availability zones. The public subnets are configured for bi-directional traffic to the\npublic internet, while the private subnets are configured for egress-only traffic to the public internet.\n\nThe module supports creating different numbers of public and private subnets per availability zone. This is useful\nfor common architectures where you need a single public subnet for load balancers but multiple private subnets\nfor different application tiers (web, app, data). You can specify the number and names of public and private\nsubnets independently using `public_subnets_per_az_count`/`public_subnets_per_az_names` and\n`private_subnets_per_az_count`/`private_subnets_per_az_names` variables.\n\nRather than provide a wealth of configuration options allowing for numerous special cases, this module\nprovides some common options and further provides the ability to suppress the creation of resources, allowing\nyou to create and configure them as you like from outside this module. For example, rather than give you the\noption to customize the Network ACL, the module gives you the option to create a completely open one (and control\naccess via Security Groups and other means) or not create one at all, allowing you to create and configure one yourself.\n\n### Public subnets\n\nThis module defines a public subnet as one that has direct access to an internet gateway and can accept incoming connection requests. \nIn the simplest configuration, the module creates a single route table with a default route targeted to the\nVPC's internet gateway, and associates all the public subnets with that single route table. \n\nLikewise it creates a single Network ACL with associated rules allowing all ingress and all egress, \nand associates that ACL with all the public subnets. \n\n### Private subnets\n\nA private subnet may be able to initiate traffic to the public internet through a NAT gateway,\na NAT instance, or an egress-only internet gateway, or it might only have direct access to other\nprivate subnets. In the simple configuration, for IPv4 and/or IPv6 with NAT64 enabled via `public_dns64_enabled`\nor `private_dns64_enabled`, the module creates 1 NAT Gateway or NAT Instance for each\nprivate subnet (in the public subnet in the same availability zone), creates 1 route table for each private subnet, \nand adds to that route table a default route from the subnet to its NAT Gateway or Instance. For IPv6,\nthe module adds a route to the Egress-Only Internet Gateway configured via input.\n\nAs with the Public subnets, the module creates a single Network ACL with associated rules allowing all ingress and \nall egress, and associates that ACL with all the private subnets. \n\n### Customization for special use cases\n\nVarious features are controlled by `bool` inputs with names ending in `_enabled`. By changing the default\nvalues, you can enable or disable creation of public subnets, private subnets, route tables, \nNAT gateways, NAT instances, or Network ACLs. So for example, you could use this module to create only\nprivate subnets and the open Network ACL, and then add your own route table associations to the subnets\nand route all non-local traffic to a Transit Gateway or VPN.\n\n### CIDR allocation\n\nFor IPv4, you provide a CIDR and the module divides the address space into the largest CIDRs possible that are still\nsmall enough to accommodate `max_subnet_count` subnets of each enabled type (public or private). When `max_subnet_count`\nis left at the default `0`, it is set to the total number of availability zones in the region. Private subnets\nare allocated out of the first half of the reserved range, and public subnets are allocated out of the second half.\n\nFor IPv6, you provide a `/56` CIDR and the module assigns `/64` subnets of that CIDR in consecutive order starting\nat zero. (You have the option of specifying a list of CIDRs instead.) As with IPv4, enough CIDRs are allocated to\ncover `max_subnet_count` private and public subnets (when both are enabled, which is the default), with the private\nsubnets being allocated out of the lower half of the reservation and the public subnets allocated out of the upper half.\n\n## Deployment Modes and Configuration\n\nThis module supports various deployment modes through flexible configuration variables. Understanding these options\nallows you to tailor the subnet architecture to your specific use case.\n\n### Availability Zone Selection\n\n**`availability_zones`** - Explicitly specify which AZs to use:\n- Provide a list of AZ names (e.g., `[\"us-east-1a\", \"us-east-1b\", \"us-east-1c\"]`)\n- The list order **must be stable** - do not reorder or Terraform will recreate subnets\n- If empty, the module uses all available AZs in the region (sorted alphabetically)\n- Can be truncated by `max_subnet_count` if you specify more AZs than the limit\n\n**`availability_zone_ids`** - Use AZ IDs instead of names:\n- Provide a list of AZ IDs (e.g., `[\"use1-az1\", \"use1-az2\"]`)\n- Overrides `availability_zones` when set\n- Useful for multi-account consistency (AZ names like \"us-east-1a\" map to different physical locations across accounts, but AZ IDs are consistent)\n- The module automatically translates IDs to names for resource creation\n\n### Subnet Count and CIDR Reservation\n\n**`max_subnet_count`** - Controls CIDR reservation for future growth:\n- Default: `0` (reserves CIDRs for all AZs in the region)\n- Recommended: Set to `3` or the maximum number of AZs you anticipate using\n- The module reserves CIDR space for this many subnets of **each type** (public and private)\n- Example: If a region has 4 AZs but you set `max_subnet_count = 3`, only 3 subnets will be created, but you can later expand to the 4th without changing existing subnet CIDRs\n- **Important**: This must be a constant value, not computed, due to Terraform limitations\n\n**`subnets_per_az_count`** - Create multiple subnets of each type per AZ:\n- Default: `1` (one public and one private subnet per AZ)\n- Set to `2` or higher to create multiple subnets per AZ\n- Creates the **same number** of public and private subnets\n- Useful for segmenting workloads within the same AZ (e.g., separate subnets for web tier, app tier, data tier)\n- Each subnet gets its own CIDR from the allocated range\n- Works with `subnets_per_az_names` for organized outputs\n\n**`subnets_per_az_names`** - Assign names to subnets for better organization:\n- Default: `[\"common\"]`\n- Provide a list of names matching `subnets_per_az_count` (e.g., `[\"web\", \"app\", \"data\"]`)\n- Names are used as keys in the `named_private_subnets_map` and `named_public_subnets_map` outputs\n- Makes it easy to reference specific subnet groups in other modules\n- Example: `module.subnets.named_private_subnets_map[\"web\"]` returns all web-tier private subnet IDs\n\n**`public_subnets_per_az_count`** - Set a different number of public subnets per AZ:\n- Default: `null` (uses `subnets_per_az_count` for backward compatibility)\n- Set this when you need a different number of public vs private subnets\n- Common pattern: Set to `1` for a single public subnet (for load balancers) while having multiple private subnets\n- Must be greater than 0 if specified\n- Works independently from `private_subnets_per_az_count`\n\n**`public_subnets_per_az_names`** - Assign names specifically to public subnets:\n- Default: `null` (uses `subnets_per_az_names` for backward compatibility)\n- Provide a list of names matching `public_subnets_per_az_count`\n- Names are used as keys in the `named_public_subnets_map` output\n- Example: `[\"public-lb\"]` for a single load balancer subnet per AZ\n\n**`private_subnets_per_az_count`** - Set a different number of private subnets per AZ:\n- Default: `null` (uses `subnets_per_az_count` for backward compatibility)\n- Set this when you need a different number of private vs public subnets\n- Common pattern: Set to `3` for multi-tier architecture (web, app, data) while having only 1 public subnet\n- Must be greater than 0 if specified\n- Works independently from `public_subnets_per_az_count`\n\n**`private_subnets_per_az_names`** - Assign names specifically to private subnets:\n- Default: `null` (uses `subnets_per_az_names` for backward compatibility)\n- Provide a list of names matching `private_subnets_per_az_count`\n- Names are used as keys in the `named_private_subnets_map` output\n- Example: `[\"web\", \"app\", \"data\"]` for a three-tier architecture\n\n### Subnet Type Selection\n\n**`public_subnets_enabled`** - Enable/disable public subnet creation:\n- Default: `true`\n- Set to `false` to create only private subnets\n- When disabled, NAT Gateways/Instances are also disabled (since they require public subnets)\n- Use case: Internal-only VPCs that route through Transit Gateway or VPN\n\n**`private_subnets_enabled`** - Enable/disable private subnet creation:\n- Default: `true`\n- Set to `false` to create only public subnets\n- When disabled, NAT Gateways/Instances are also disabled (since private subnets don't need them)\n- Use case: DMZ or edge VPCs with only internet-facing resources\n\n### NAT Configuration and Cost Optimization\n\n**`max_nats`** - Limit the number of NAT devices for cost savings:\n- Default: `999` (creates one NAT per AZ for high availability)\n- Set to `1` for cost savings (single NAT, reduced availability)\n- Set to `2` for balance between cost and availability (two NATs across AZs)\n- **Cost impact**: Each NAT Gateway costs ~$32/month plus data transfer fees\n- **Availability impact**: If the NAT fails (or its AZ fails), private subnets lose internet access\n- The module distributes NAT devices across the first N availability zones\n- Example: With 3 AZs and `max_nats = 1`, only the first AZ gets a NAT Gateway\n\n**`nat_gateway_public_subnet_indices`** - Control which public subnet gets the NAT Gateway (by index):\n- Default: `[0]` (place NAT in the first public subnet of each AZ)\n- When you have multiple public subnets per AZ, this determines which one hosts the NAT Gateway\n- NAT Gateways are shared - one NAT per AZ serves all private subnets in that AZ\n- **Important**: Each subnet index must be less than `public_subnets_per_az_count`\n- Example: With `public_subnets_per_az_count = 2` and `nat_gateway_public_subnet_indices = [0]`, the NAT goes in the first public subnet\n- Advanced: Set to `[0, 1]` to create redundant NATs within each AZ (rarely needed, increases cost)\n- Cannot be used with `nat_gateway_public_subnet_names` (choose indices OR names, not both)\n\n**`nat_gateway_public_subnet_names`** - Control which public subnet gets the NAT Gateway (by name):\n- Default: `null` (uses `nat_gateway_public_subnet_indices` instead)\n- **More intuitive alternative** to using indices - specify subnets by name\n- References the names from `public_subnets_per_az_names`\n- Example: `[\"loadbalancer\"]` places NAT in the \"loadbalancer\" subnet\n- Example: `[\"loadbalancer\", \"web\"]` creates 2 NATs per AZ in both named subnets (expensive)\n- Cannot be used with `nat_gateway_public_subnet_indices` (choose indices OR names, not both)\n- **Recommended approach** for clarity and maintainability\n\n### Common Deployment Patterns\n\n**Standard HA deployment** (default):\n```hcl\n# 1 public + 1 private subnet per AZ, with NAT Gateway per AZ\npublic_subnets_enabled  = true\nprivate_subnets_enabled = true\nmax_subnet_count        = 3  # Reserve space for 3 AZs\nmax_nats                = 999 # One NAT per AZ\n```\n\n**Cost-optimized deployment**:\n```hcl\n# Single NAT Gateway shared across all private subnets\nmax_nats = 1\n# Everything else default\n```\n\n**Private-only with Transit Gateway**:\n```hcl\n# Private subnets only, routing through TGW\npublic_subnets_enabled  = false\nprivate_subnets_enabled = true\nnat_gateway_enabled     = false\n# Add custom routes to TGW externally\n```\n\n**Public-only (DMZ) deployment**:\n```hcl\n# Public subnets only for internet-facing resources\npublic_subnets_enabled  = true\nprivate_subnets_enabled = false\n```\n\n**Multi-tier architecture per AZ** (legacy approach - same number of public and private):\n```hcl\n# 3 private AND 3 public subnets per AZ (web, app, data)\nsubnets_per_az_count = 3\nsubnets_per_az_names = [\"web\", \"app\", \"data\"]\n# Access subnets via: named_private_subnets_map[\"web\"]\n```\n\n**Multi-tier with separate public/private counts** (recommended):\n```hcl\n# 1 public subnet per AZ for load balancers\n# 3 private subnets per AZ for web, app, and data tiers\npublic_subnets_per_az_count  = 1\npublic_subnets_per_az_names  = [\"public-lb\"]\nprivate_subnets_per_az_count = 3\nprivate_subnets_per_az_names = [\"web\", \"app\", \"data\"]\n# NAT Gateway automatically goes in the first (and only) public subnet\n# Can omit nat_gateway config since there's only one public subnet\n# Access subnets via:\n#   named_public_subnets_map[\"public-lb\"]\n#   named_private_subnets_map[\"web\"]\n#   named_private_subnets_map[\"app\"]\n#   named_private_subnets_map[\"data\"]\n```\n\n**Multiple public subnets with controlled NAT placement**:\n```hcl\n# 2 public subnets per AZ: one for ALB, one for bastion hosts\n# Place NAT Gateway in the ALB subnet\npublic_subnets_per_az_count = 2\npublic_subnets_per_az_names = [\"alb\", \"bastion\"]\n\n# OPTION 1: Use subnet name (recommended - more readable)\nnat_gateway_public_subnet_names = [\"alb\"]\n\n# OPTION 2: Use subnet index (alternative)\n# nat_gateway_public_subnet_indices = [0]  # 0 = first subnet = \"alb\"\n\n# Result: 1 NAT per AZ in the \"alb\" subnet, shared by all private subnets\n```\n\n**Multiple private + multiple public with one NAT in specific subnet**:\n```hcl\n# Real-world example: Database, app tiers + load balancer and web frontends\n# 3 private subnets per AZ (database, app1, app2)\n# 2 public subnets per AZ (loadbalancer, web)\n# 1 NAT Gateway per AZ in the \"loadbalancer\" subnet\n\navailability_zones = [\"us-east-1a\", \"us-east-1b\", \"us-east-1c\"]\n\nprivate_subnets_per_az_count = 3\nprivate_subnets_per_az_names = [\"database\", \"app1\", \"app2\"]\n\npublic_subnets_per_az_count  = 2\npublic_subnets_per_az_names  = [\"loadbalancer\", \"web\"]\n\n# Place NAT Gateway in the \"loadbalancer\" subnet (by name)\nnat_gateway_public_subnet_names = [\"loadbalancer\"]\n\n# Result per AZ:\n# - 3 private subnets: database, app1, app2\n# - 2 public subnets: loadbalancer, web\n# - 1 NAT Gateway in \"loadbalancer\" subnet\n# - All 3 private subnets route to the same NAT\n# Total: 3 NAT Gateways (one per AZ) = ~$96/month\n```\n\n**Multiple private + multiple public with NAT in EACH public subnet** (high availability):\n```hcl\n# Advanced: Redundant NAT Gateways within each AZ for maximum availability\n# 3 private subnets per AZ (database, app1, app2)\n# 2 public subnets per AZ (loadbalancer, web)\n# 2 NAT Gateways per AZ (one in each public subnet)\n\navailability_zones = [\"us-east-1a\", \"us-east-1b\", \"us-east-1c\"]\n\nprivate_subnets_per_az_count = 3\nprivate_subnets_per_az_names = [\"database\", \"app1\", \"app2\"]\n\npublic_subnets_per_az_count  = 2\npublic_subnets_per_az_names  = [\"loadbalancer\", \"web\"]\n\n# Place NAT Gateways in BOTH public subnets (by name)\nnat_gateway_public_subnet_names = [\"loadbalancer\", \"web\"]\n\n# Alternative using indices:\n# nat_gateway_public_subnet_indices = [0, 1]\n\n# Result per AZ:\n# - 3 private subnets: database, app1, app2\n# - 2 public subnets: loadbalancer, web\n# - 2 NAT Gateways: one in \"loadbalancer\", one in \"web\"\n# - Private subnets distributed across NATs:\n#   - \"database\" → NAT in \"loadbalancer\"\n#   - \"app1\" → NAT in \"web\"\n#   - \"app2\" → NAT in \"loadbalancer\"\n# Total: 6 NAT Gateways (2 per AZ × 3 AZs) = ~$192/month\n# WARNING: This is expensive. Use only if you need intra-AZ NAT redundancy.\n```\n\n### NAT Gateway ID References in Outputs\n\nThe module exposes NAT Gateway IDs in the subnet stats outputs, enabling downstream components like network\nfirewalls to reference the NAT Gateways associated with each subnet.\n\n**`named_private_subnets_stats_map`** - Each private subnet includes the NAT Gateway ID it routes to:\n```hcl\n# Output structure (4 fields per subnet):\nnamed_private_subnets_stats_map = {\n  \"database\" = [\n    {\n      az             = \"us-east-2a\"\n      subnet_id      = \"subnet-abc123\"\n      route_table_id = \"rtb-def456\"\n      nat_gateway_id = \"nat-xyz789\"  # NAT Gateway this subnet routes to for egress\n    },\n    # ... one entry per AZ\n  ]\n  \"app1\" = [ ... ]\n  \"app2\" = [ ... ]\n}\n```\n\n**`named_public_subnets_stats_map`** - Each public subnet includes the NAT Gateway ID if one exists in that subnet:\n```hcl\n# Output structure (4 fields per subnet):\nnamed_public_subnets_stats_map = {\n  \"loadbalancer\" = [\n    {\n      az             = \"us-east-2a\"\n      subnet_id      = \"subnet-ghi789\"\n      route_table_id = \"rtb-jkl012\"\n      nat_gateway_id = \"nat-xyz789\"  # NAT Gateway in this public subnet (if any)\n    },\n    # ... one entry per AZ\n  ]\n  \"web\" = [ ... ]\n}\n```\n\n**Use case example** - Network firewall routing:\n```hcl\n# Reference NAT Gateway IDs from subnet stats\nlocals {\n  database_nat_gateways = [\n    for stats in module.subnets.named_private_subnets_stats_map[\"database\"] :\n    stats.nat_gateway_id if stats.nat_gateway_id != \"\"\n  ]\n}\n\n# Use in network firewall route configuration\nresource \"aws_networkfirewall_firewall_policy\" \"example\" {\n  # ... configuration that needs NAT Gateway IDs\n}\n```\n\n**Multi-account with consistent AZs**:\n```hcl\n# Use AZ IDs for consistency across accounts\navailability_zone_ids = [\"use1-az1\", \"use1-az2\", \"use1-az4\"]\n# These map to the same physical locations across all accounts\n```\n\n\n\u003e [!TIP]\n\u003e #### 👽 Use Atmos with Terraform\n\u003e Cloud Posse uses [`atmos`](https://atmos.tools) to easily orchestrate multiple environments using Terraform. \u003cbr/\u003e\n\u003e Works with [Github Actions](https://atmos.tools/integrations/github-actions/), [Atlantis](https://atmos.tools/integrations/atlantis), or [Spacelift](https://atmos.tools/integrations/spacelift).\n\u003e\n\u003e \u003cdetails\u003e\n\u003e \u003csummary\u003e\u003cstrong\u003eWatch demo of using Atmos with Terraform\u003c/strong\u003e\u003c/summary\u003e\n\u003e \u003cimg src=\"https://github.com/cloudposse/atmos/blob/main/docs/demo.gif?raw=true\"/\u003e\u003cbr/\u003e\n\u003e \u003ci\u003eExample of running \u003ca href=\"https://atmos.tools\"\u003e\u003ccode\u003eatmos\u003c/code\u003e\u003c/a\u003e to manage infrastructure from our \u003ca href=\"https://atmos.tools/quick-start/\"\u003eQuick Start\u003c/a\u003e tutorial.\u003c/i\u003e\n\u003e \u003c/detalis\u003e\n\n\n\n\n\n## Usage\n\n```hcl\nmodule \"subnets\" {\n  source = \"cloudposse/dynamic-subnets/aws\"\n  # Cloud Posse recommends pinning every module to a specific version\n  # version = \"x.x.x\"\n  namespace           = \"eg\"\n  stage               = \"prod\"\n  name                = \"app\"\n  vpc_id              = \"vpc-XXXXXXXX\"\n  igw_id              = [\"igw-XXXXXXXX\"]\n  ipv4_cidr_block     = [\"10.0.0.0/16\"]\n  availability_zones  = [\"us-east-1a\", \"us-east-1b\"]\n}\n```\n\nCreate only private subnets, route to transit gateway:\n\n```hcl\nmodule \"private_tgw_subnets\" {\n  source = \"cloudposse/dynamic-subnets/aws\"\n  # Cloud Posse recommends pinning every module to a specific version\n  # version = \"x.x.x\"\n  namespace           = \"eg\"\n  stage               = \"prod\"\n  name                = \"app\"\n  vpc_id              = \"vpc-XXXXXXXX\"\n  igw_id              = [\"igw-XXXXXXXX\"]\n  ipv4_cidr_block     = [\"10.0.0.0/16\"]\n  availability_zones  = [\"us-east-1a\", \"us-east-1b\"]\n\n  nat_gateway_enabled    = false\n  public_subnets_enabled = false\n}\n\nresource \"aws_route\" \"private\" {\n  count = length(module.private_tgw_subnets.private_route_table_ids)\n\n  route_table_id         = module.private_tgw_subnets.private_route_table_ids[count.index]\n  destination_cidr_block = \"0.0.0.0/0\"\n  transit_gateway_id     = \"tgw-XXXXXXXXX\"\n}\n```\n\nSee [examples](examples) for working examples. In particular, see [examples/nacls](examples/nacls) \nfor an example of how to create custom Network Access Control Lists (NACLs) outside of\nbut in conjunction with this module.\n\n\u003e [!IMPORTANT]\n\u003e In Cloud Posse's examples, we avoid pinning modules to specific versions to prevent discrepancies between the documentation\n\u003e and the latest released versions. However, for your own projects, we strongly advise pinning each module to the exact version\n\u003e you're using. This practice ensures the stability of your infrastructure. Additionally, we recommend implementing a systematic\n\u003e approach for updating versions to avoid unexpected changes.\n\n\n\n\n\n\n\n\n\u003c!-- markdownlint-disable --\u003e\n## Requirements\n\n| Name | Version |\n|------|---------|\n| \u003ca name=\"requirement_terraform\"\u003e\u003c/a\u003e [terraform](#requirement\\_terraform) | \u003e= 1.1.0 |\n| \u003ca name=\"requirement_aws\"\u003e\u003c/a\u003e [aws](#requirement\\_aws) | \u003e= 5.0 |\n\n## Providers\n\n| Name | Version |\n|------|---------|\n| \u003ca name=\"provider_aws\"\u003e\u003c/a\u003e [aws](#provider\\_aws) | \u003e= 5.0 |\n\n## Modules\n\n| Name | Source | Version |\n|------|--------|---------|\n| \u003ca name=\"module_nat_instance_label\"\u003e\u003c/a\u003e [nat\\_instance\\_label](#module\\_nat\\_instance\\_label) | cloudposse/label/null | 0.25.0 |\n| \u003ca name=\"module_nat_label\"\u003e\u003c/a\u003e [nat\\_label](#module\\_nat\\_label) | cloudposse/label/null | 0.25.0 |\n| \u003ca name=\"module_private_label\"\u003e\u003c/a\u003e [private\\_label](#module\\_private\\_label) | cloudposse/label/null | 0.25.0 |\n| \u003ca name=\"module_public_label\"\u003e\u003c/a\u003e [public\\_label](#module\\_public\\_label) | cloudposse/label/null | 0.25.0 |\n| \u003ca name=\"module_this\"\u003e\u003c/a\u003e [this](#module\\_this) | cloudposse/label/null | 0.25.0 |\n| \u003ca name=\"module_utils\"\u003e\u003c/a\u003e [utils](#module\\_utils) | cloudposse/utils/aws | 1.4.0 |\n\n## Resources\n\n| Name | Type |\n|------|------|\n| [aws_eip.default](https://registry.terraform.io/providers/hashicorp/aws/latest/docs/resources/eip) | resource |\n| [aws_eip_association.nat_instance](https://registry.terraform.io/providers/hashicorp/aws/latest/docs/resources/eip_association) | resource |\n| [aws_instance.nat_instance](https://registry.terraform.io/providers/hashicorp/aws/latest/docs/resources/instance) | resource |\n| [aws_nat_gateway.default](https://registry.terraform.io/providers/hashicorp/aws/latest/docs/resources/nat_gateway) | resource |\n| [aws_network_acl.private](https://registry.terraform.io/providers/hashicorp/aws/latest/docs/resources/network_acl) | resource |\n| [aws_network_acl.public](https://registry.terraform.io/providers/hashicorp/aws/latest/docs/resources/network_acl) | resource |\n| [aws_network_acl_rule.private4_egress](https://registry.terraform.io/providers/hashicorp/aws/latest/docs/resources/network_acl_rule) | resource |\n| [aws_network_acl_rule.private4_ingress](https://registry.terraform.io/providers/hashicorp/aws/latest/docs/resources/network_acl_rule) | resource |\n| [aws_network_acl_rule.private6_egress](https://registry.terraform.io/providers/hashicorp/aws/latest/docs/resources/network_acl_rule) | resource |\n| [aws_network_acl_rule.private6_ingress](https://registry.terraform.io/providers/hashicorp/aws/latest/docs/resources/network_acl_rule) | resource |\n| [aws_network_acl_rule.public4_egress](https://registry.terraform.io/providers/hashicorp/aws/latest/docs/resources/network_acl_rule) | resource |\n| [aws_network_acl_rule.public4_ingress](https://registry.terraform.io/providers/hashicorp/aws/latest/docs/resources/network_acl_rule) | resource |\n| [aws_network_acl_rule.public6_egress](https://registry.terraform.io/providers/hashicorp/aws/latest/docs/resources/network_acl_rule) | resource |\n| [aws_network_acl_rule.public6_ingress](https://registry.terraform.io/providers/hashicorp/aws/latest/docs/resources/network_acl_rule) | resource |\n| [aws_route.nat4](https://registry.terraform.io/providers/hashicorp/aws/latest/docs/resources/route) | resource |\n| [aws_route.nat_instance](https://registry.terraform.io/providers/hashicorp/aws/latest/docs/resources/route) | resource |\n| [aws_route.private6](https://registry.terraform.io/providers/hashicorp/aws/latest/docs/resources/route) | resource |\n| [aws_route.private_nat64](https://registry.terraform.io/providers/hashicorp/aws/latest/docs/resources/route) | resource |\n| [aws_route.public](https://registry.terraform.io/providers/hashicorp/aws/latest/docs/resources/route) | resource |\n| [aws_route.public6](https://registry.terraform.io/providers/hashicorp/aws/latest/docs/resources/route) | resource |\n| [aws_route.public_nat64](https://registry.terraform.io/providers/hashicorp/aws/latest/docs/resources/route) | resource |\n| [aws_route_table.private](https://registry.terraform.io/providers/hashicorp/aws/latest/docs/resources/route_table) | resource |\n| [aws_route_table.public](https://registry.terraform.io/providers/hashicorp/aws/latest/docs/resources/route_table) | resource |\n| [aws_route_table_association.private](https://registry.terraform.io/providers/hashicorp/aws/latest/docs/resources/route_table_association) | resource |\n| [aws_route_table_association.public](https://registry.terraform.io/providers/hashicorp/aws/latest/docs/resources/route_table_association) | resource |\n| [aws_security_group.nat_instance](https://registry.terraform.io/providers/hashicorp/aws/latest/docs/resources/security_group) | resource |\n| [aws_security_group_rule.nat_instance_egress](https://registry.terraform.io/providers/hashicorp/aws/latest/docs/resources/security_group_rule) | resource |\n| [aws_security_group_rule.nat_instance_ingress](https://registry.terraform.io/providers/hashicorp/aws/latest/docs/resources/security_group_rule) | resource |\n| [aws_subnet.private](https://registry.terraform.io/providers/hashicorp/aws/latest/docs/resources/subnet) | resource |\n| [aws_subnet.public](https://registry.terraform.io/providers/hashicorp/aws/latest/docs/resources/subnet) | resource |\n| [aws_ami.nat_instance](https://registry.terraform.io/providers/hashicorp/aws/latest/docs/data-sources/ami) | data source |\n| [aws_availability_zones.default](https://registry.terraform.io/providers/hashicorp/aws/latest/docs/data-sources/availability_zones) | data source |\n| [aws_eip.nat](https://registry.terraform.io/providers/hashicorp/aws/latest/docs/data-sources/eip) | data source |\n| [aws_vpc.default](https://registry.terraform.io/providers/hashicorp/aws/latest/docs/data-sources/vpc) | data source |\n\n## Inputs\n\n| Name | Description | Type | Default | Required |\n|------|-------------|------|---------|:--------:|\n| \u003ca name=\"input_additional_tag_map\"\u003e\u003c/a\u003e [additional\\_tag\\_map](#input\\_additional\\_tag\\_map) | Additional key-value pairs to add to each map in `tags_as_list_of_maps`. Not added to `tags` or `id`.\u003cbr/\u003eThis is for some rare cases where resources want additional configuration of tags\u003cbr/\u003eand therefore take a list of maps with tag key, value, and additional configuration. | `map(string)` | `{}` | no |\n| \u003ca name=\"input_attributes\"\u003e\u003c/a\u003e [attributes](#input\\_attributes) | ID element. Additional attributes (e.g. `workers` or `cluster`) to add to `id`,\u003cbr/\u003ein the order they appear in the list. New attributes are appended to the\u003cbr/\u003eend of the list. The elements of the list are joined by the `delimiter`\u003cbr/\u003eand treated as a single ID element. | `list(string)` | `[]` | no |\n| \u003ca name=\"input_availability_zone_attribute_style\"\u003e\u003c/a\u003e [availability\\_zone\\_attribute\\_style](#input\\_availability\\_zone\\_attribute\\_style) | The style of Availability Zone code to use in tags and names. One of `full`, `short`, or `fixed`.\u003cbr/\u003eWhen using `availability_zone_ids`, IDs will first be translated into AZ names. | `string` | `\"short\"` | no |\n| \u003ca name=\"input_availability_zone_ids\"\u003e\u003c/a\u003e [availability\\_zone\\_ids](#input\\_availability\\_zone\\_ids) | List of Availability Zones IDs where subnets will be created. Overrides `availability_zones`.\u003cbr/\u003eUseful in some regions when using only some AZs and you want to use the same ones across multiple accounts. | `list(string)` | `[]` | no |\n| \u003ca name=\"input_availability_zones\"\u003e\u003c/a\u003e [availability\\_zones](#input\\_availability\\_zones) | List of Availability Zones (AZs) where subnets will be created. Ignored when `availability_zone_ids` is set.\u003cbr/\u003eThe order of zones in the list ***must be stable*** or else Terraform will continually make changes.\u003cbr/\u003eIf no AZs are specified, then `max_subnet_count` AZs will be selected in alphabetical order.\u003cbr/\u003eIf `max_subnet_count \u003e 0` and `length(var.availability_zones) \u003e max_subnet_count`, the list\u003cbr/\u003ewill be truncated. We recommend setting `availability_zones` and `max_subnet_count` explicitly as constant\u003cbr/\u003e(not computed) values for predictability, consistency, and stability. | `list(string)` | `[]` | no |\n| \u003ca name=\"input_aws_route_create_timeout\"\u003e\u003c/a\u003e [aws\\_route\\_create\\_timeout](#input\\_aws\\_route\\_create\\_timeout) | DEPRECATED: Use `route_create_timeout` instead.\u003cbr/\u003eTime to wait for AWS route creation, specified as a Go Duration, e.g. `2m` | `string` | `null` | no |\n| \u003ca name=\"input_aws_route_delete_timeout\"\u003e\u003c/a\u003e [aws\\_route\\_delete\\_timeout](#input\\_aws\\_route\\_delete\\_timeout) | DEPRECATED: Use `route_delete_timeout` instead.\u003cbr/\u003eTime to wait for AWS route deletion, specified as a Go Duration, e.g. `2m` | `string` | `null` | no |\n| \u003ca name=\"input_context\"\u003e\u003c/a\u003e [context](#input\\_context) | Single object for setting entire context at once.\u003cbr/\u003eSee description of individual variables for details.\u003cbr/\u003eLeave string and numeric variables as `null` to use default value.\u003cbr/\u003eIndividual variable settings (non-null) override settings in context object,\u003cbr/\u003eexcept for attributes, tags, and additional\\_tag\\_map, which are merged. | `any` | \u003cpre\u003e{\u003cbr/\u003e  \"additional_tag_map\": {},\u003cbr/\u003e  \"attributes\": [],\u003cbr/\u003e  \"delimiter\": null,\u003cbr/\u003e  \"descriptor_formats\": {},\u003cbr/\u003e  \"enabled\": true,\u003cbr/\u003e  \"environment\": null,\u003cbr/\u003e  \"id_length_limit\": null,\u003cbr/\u003e  \"label_key_case\": null,\u003cbr/\u003e  \"label_order\": [],\u003cbr/\u003e  \"label_value_case\": null,\u003cbr/\u003e  \"labels_as_tags\": [\u003cbr/\u003e    \"unset\"\u003cbr/\u003e  ],\u003cbr/\u003e  \"name\": null,\u003cbr/\u003e  \"namespace\": null,\u003cbr/\u003e  \"regex_replace_chars\": null,\u003cbr/\u003e  \"stage\": null,\u003cbr/\u003e  \"tags\": {},\u003cbr/\u003e  \"tenant\": null\u003cbr/\u003e}\u003c/pre\u003e | no |\n| \u003ca name=\"input_delimiter\"\u003e\u003c/a\u003e [delimiter](#input\\_delimiter) | Delimiter to be used between ID elements.\u003cbr/\u003eDefaults to `-` (hyphen). Set to `\"\"` to use no delimiter at all. | `string` | `null` | no |\n| \u003ca name=\"input_descriptor_formats\"\u003e\u003c/a\u003e [descriptor\\_formats](#input\\_descriptor\\_formats) | Describe additional descriptors to be output in the `descriptors` output map.\u003cbr/\u003eMap of maps. Keys are names of descriptors. Values are maps of the form\u003cbr/\u003e`{\u003cbr/\u003e   format = string\u003cbr/\u003e   labels = list(string)\u003cbr/\u003e}`\u003cbr/\u003e(Type is `any` so the map values can later be enhanced to provide additional options.)\u003cbr/\u003e`format` is a Terraform format string to be passed to the `format()` function.\u003cbr/\u003e`labels` is a list of labels, in order, to pass to `format()` function.\u003cbr/\u003eLabel values will be normalized before being passed to `format()` so they will be\u003cbr/\u003eidentical to how they appear in `id`.\u003cbr/\u003eDefault is `{}` (`descriptors` output will be empty). | `any` | `{}` | no |\n| \u003ca name=\"input_enabled\"\u003e\u003c/a\u003e [enabled](#input\\_enabled) | Set to false to prevent the module from creating any resources | `bool` | `null` | no |\n| \u003ca name=\"input_environment\"\u003e\u003c/a\u003e [environment](#input\\_environment) | ID element. Usually used for region e.g. 'uw2', 'us-west-2', OR role 'prod', 'staging', 'dev', 'UAT' | `string` | `null` | no |\n| \u003ca name=\"input_id_length_limit\"\u003e\u003c/a\u003e [id\\_length\\_limit](#input\\_id\\_length\\_limit) | Limit `id` to this many characters (minimum 6).\u003cbr/\u003eSet to `0` for unlimited length.\u003cbr/\u003eSet to `null` for keep the existing setting, which defaults to `0`.\u003cbr/\u003eDoes not affect `id_full`. | `number` | `null` | no |\n| \u003ca name=\"input_igw_id\"\u003e\u003c/a\u003e [igw\\_id](#input\\_igw\\_id) | The Internet Gateway ID that the public subnets will route traffic to.\u003cbr/\u003eUsed if `public_route_table_enabled` is `true`, ignored otherwise. | `list(string)` | `[]` | no |\n| \u003ca name=\"input_ipv4_cidr_block\"\u003e\u003c/a\u003e [ipv4\\_cidr\\_block](#input\\_ipv4\\_cidr\\_block) | Base IPv4 CIDR block which will be divided into subnet CIDR blocks (e.g. `10.0.0.0/16`). Ignored if `ipv4_cidrs` is set.\u003cbr/\u003eIf no CIDR block is provided, the VPC's default IPv4 CIDR block will be used. | `list(string)` | `[]` | no |\n| \u003ca name=\"input_ipv4_cidrs\"\u003e\u003c/a\u003e [ipv4\\_cidrs](#input\\_ipv4\\_cidrs) | Lists of CIDRs to assign to subnets. Order of CIDRs in the lists must not change over time.\u003cbr/\u003eLists may contain more CIDRs than needed. | \u003cpre\u003elist(object({\u003cbr/\u003e    private = list(string)\u003cbr/\u003e    public  = list(string)\u003cbr/\u003e  }))\u003c/pre\u003e | `[]` | no |\n| \u003ca name=\"input_ipv4_enabled\"\u003e\u003c/a\u003e [ipv4\\_enabled](#input\\_ipv4\\_enabled) | Set `true` to enable IPv4 addresses in the subnets | `bool` | `true` | no |\n| \u003ca name=\"input_ipv4_private_instance_hostname_type\"\u003e\u003c/a\u003e [ipv4\\_private\\_instance\\_hostname\\_type](#input\\_ipv4\\_private\\_instance\\_hostname\\_type) | How to generate the DNS name for the instances in the private subnets.\u003cbr/\u003eEither `ip-name` to generate it from the IPv4 address, or\u003cbr/\u003e`resource-name` to generate it from the instance ID. | `string` | `\"ip-name\"` | no |\n| \u003ca name=\"input_ipv4_private_instance_hostnames_enabled\"\u003e\u003c/a\u003e [ipv4\\_private\\_instance\\_hostnames\\_enabled](#input\\_ipv4\\_private\\_instance\\_hostnames\\_enabled) | If `true`, DNS queries for instance hostnames in the private subnets will be answered with A (IPv4) records. | `bool` | `false` | no |\n| \u003ca name=\"input_ipv4_public_instance_hostname_type\"\u003e\u003c/a\u003e [ipv4\\_public\\_instance\\_hostname\\_type](#input\\_ipv4\\_public\\_instance\\_hostname\\_type) | How to generate the DNS name for the instances in the public subnets.\u003cbr/\u003eEither `ip-name` to generate it from the IPv4 address, or\u003cbr/\u003e`resource-name` to generate it from the instance ID. | `string` | `\"ip-name\"` | no |\n| \u003ca name=\"input_ipv4_public_instance_hostnames_enabled\"\u003e\u003c/a\u003e [ipv4\\_public\\_instance\\_hostnames\\_enabled](#input\\_ipv4\\_public\\_instance\\_hostnames\\_enabled) | If `true`, DNS queries for instance hostnames in the public subnets will be answered with A (IPv4) records. | `bool` | `false` | no |\n| \u003ca name=\"input_ipv6_cidr_block\"\u003e\u003c/a\u003e [ipv6\\_cidr\\_block](#input\\_ipv6\\_cidr\\_block) | Base IPv6 CIDR block from which `/64` subnet CIDRs will be assigned. Must be `/56`. (e.g. `2600:1f16:c52:ab00::/56`).\u003cbr/\u003eIgnored if `ipv6_cidrs` is set. If no CIDR block is provided, the VPC's default IPv6 CIDR block will be used. | `list(string)` | `[]` | no |\n| \u003ca name=\"input_ipv6_cidrs\"\u003e\u003c/a\u003e [ipv6\\_cidrs](#input\\_ipv6\\_cidrs) | Lists of CIDRs to assign to subnets. Order of CIDRs in the lists must not change over time.\u003cbr/\u003eLists may contain more CIDRs than needed. | \u003cpre\u003elist(object({\u003cbr/\u003e    private = list(string)\u003cbr/\u003e    public  = list(string)\u003cbr/\u003e  }))\u003c/pre\u003e | `[]` | no |\n| \u003ca name=\"input_ipv6_egress_only_igw_id\"\u003e\u003c/a\u003e [ipv6\\_egress\\_only\\_igw\\_id](#input\\_ipv6\\_egress\\_only\\_igw\\_id) | The Egress Only Internet Gateway ID the private IPv6 subnets will route traffic to.\u003cbr/\u003eUsed if `private_route_table_enabled` is `true` and `ipv6_enabled` is `true`, ignored otherwise. | `list(string)` | `[]` | no |\n| \u003ca name=\"input_ipv6_enabled\"\u003e\u003c/a\u003e [ipv6\\_enabled](#input\\_ipv6\\_enabled) | Set `true` to enable IPv6 addresses in the subnets | `bool` | `false` | no |\n| \u003ca name=\"input_ipv6_private_instance_hostnames_enabled\"\u003e\u003c/a\u003e [ipv6\\_private\\_instance\\_hostnames\\_enabled](#input\\_ipv6\\_private\\_instance\\_hostnames\\_enabled) | If `true` (or if `ipv4_enabled` is `false`), DNS queries for instance hostnames in the private subnets will be answered with AAAA (IPv6) records. | `bool` | `false` | no |\n| \u003ca name=\"input_ipv6_public_instance_hostnames_enabled\"\u003e\u003c/a\u003e [ipv6\\_public\\_instance\\_hostnames\\_enabled](#input\\_ipv6\\_public\\_instance\\_hostnames\\_enabled) | If `true` (or if `ipv4_enabled` is false), DNS queries for instance hostnames in the public subnets will be answered with AAAA (IPv6) records. | `bool` | `false` | no |\n| \u003ca name=\"input_label_key_case\"\u003e\u003c/a\u003e [label\\_key\\_case](#input\\_label\\_key\\_case) | Controls the letter case of the `tags` keys (label names) for tags generated by this module.\u003cbr/\u003eDoes not affect keys of tags passed in via the `tags` input.\u003cbr/\u003ePossible values: `lower`, `title`, `upper`.\u003cbr/\u003eDefault value: `title`. | `string` | `null` | no |\n| \u003ca name=\"input_label_order\"\u003e\u003c/a\u003e [label\\_order](#input\\_label\\_order) | The order in which the labels (ID elements) appear in the `id`.\u003cbr/\u003eDefaults to [\"namespace\", \"environment\", \"stage\", \"name\", \"attributes\"].\u003cbr/\u003eYou can omit any of the 6 labels (\"tenant\" is the 6th), but at least one must be present. | `list(string)` | `null` | no |\n| \u003ca name=\"input_label_value_case\"\u003e\u003c/a\u003e [label\\_value\\_case](#input\\_label\\_value\\_case) | Controls the letter case of ID elements (labels) as included in `id`,\u003cbr/\u003eset as tag values, and output by this module individually.\u003cbr/\u003eDoes not affect values of tags passed in via the `tags` input.\u003cbr/\u003ePossible values: `lower`, `title`, `upper` and `none` (no transformation).\u003cbr/\u003eSet this to `title` and set `delimiter` to `\"\"` to yield Pascal Case IDs.\u003cbr/\u003eDefault value: `lower`. | `string` | `null` | no |\n| \u003ca name=\"input_labels_as_tags\"\u003e\u003c/a\u003e [labels\\_as\\_tags](#input\\_labels\\_as\\_tags) | Set of labels (ID elements) to include as tags in the `tags` output.\u003cbr/\u003eDefault is to include all labels.\u003cbr/\u003eTags with empty values will not be included in the `tags` output.\u003cbr/\u003eSet to `[]` to suppress all generated tags.\u003cbr/\u003e**Notes:**\u003cbr/\u003e  The value of the `name` tag, if included, will be the `id`, not the `name`.\u003cbr/\u003e  Unlike other `null-label` inputs, the initial setting of `labels_as_tags` cannot be\u003cbr/\u003e  changed in later chained modules. Attempts to change it will be silently ignored. | `set(string)` | \u003cpre\u003e[\u003cbr/\u003e  \"default\"\u003cbr/\u003e]\u003c/pre\u003e | no |\n| \u003ca name=\"input_map_public_ip_on_launch\"\u003e\u003c/a\u003e [map\\_public\\_ip\\_on\\_launch](#input\\_map\\_public\\_ip\\_on\\_launch) | If `true`, instances launched into a public subnet will be assigned a public IPv4 address | `bool` | `true` | no |\n| \u003ca name=\"input_max_nats\"\u003e\u003c/a\u003e [max\\_nats](#input\\_max\\_nats) | Upper limit on number of NAT Gateways/Instances to create.\u003cbr/\u003eSet to 1 or 2 for cost savings at the expense of availability. | `number` | `999` | no |\n| \u003ca name=\"input_max_subnet_count\"\u003e\u003c/a\u003e [max\\_subnet\\_count](#input\\_max\\_subnet\\_count) | Sets the maximum number of each type (public or private) of subnet to deploy.\u003cbr/\u003e`0` will reserve a CIDR for every Availability Zone (excluding Local Zones) in the region, and\u003cbr/\u003edeploy a subnet in each availability zone specified in `availability_zones` or `availability_zone_ids`,\u003cbr/\u003eor every zone if none are specified. We recommend setting this equal to the maximum number of AZs you anticipate using,\u003cbr/\u003eto avoid causing subnets to be destroyed and recreated with smaller IPv4 CIDRs when AWS adds an availability zone.\u003cbr/\u003eDue to Terraform limitations, you can not set `max_subnet_count` from a computed value, you have to set it\u003cbr/\u003efrom an explicit constant. For most cases, `3` is a good choice. | `number` | `0` | no |\n| \u003ca name=\"input_metadata_http_endpoint_enabled\"\u003e\u003c/a\u003e [metadata\\_http\\_endpoint\\_enabled](#input\\_metadata\\_http\\_endpoint\\_enabled) | Whether the metadata service is available on the created NAT instances | `bool` | `true` | no |\n| \u003ca name=\"input_metadata_http_put_response_hop_limit\"\u003e\u003c/a\u003e [metadata\\_http\\_put\\_response\\_hop\\_limit](#input\\_metadata\\_http\\_put\\_response\\_hop\\_limit) | The desired HTTP PUT response hop limit (between 1 and 64) for instance metadata requests on the created NAT instances | `number` | `1` | no |\n| \u003ca name=\"input_metadata_http_tokens_required\"\u003e\u003c/a\u003e [metadata\\_http\\_tokens\\_required](#input\\_metadata\\_http\\_tokens\\_required) | Whether or not the metadata service requires session tokens, also referred to as Instance Metadata Service Version 2, on the created NAT instances | `bool` | `true` | no |\n| \u003ca name=\"input_name\"\u003e\u003c/a\u003e [name](#input\\_name) | ID element. Usually the component or solution name, e.g. 'app' or 'jenkins'.\u003cbr/\u003eThis is the only ID element not also included as a `tag`.\u003cbr/\u003eThe \"name\" tag is set to the full `id` string. There is no tag with the value of the `name` input. | `string` | `null` | no |\n| \u003ca name=\"input_namespace\"\u003e\u003c/a\u003e [namespace](#input\\_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 |\n| \u003ca name=\"input_nat_elastic_ips\"\u003e\u003c/a\u003e [nat\\_elastic\\_ips](#input\\_nat\\_elastic\\_ips) | Existing Elastic IPs (not EIP IDs) to attach to the NAT Gateway(s) or Instance(s) instead of creating new ones. | `list(string)` | `[]` | no |\n| \u003ca name=\"input_nat_gateway_enabled\"\u003e\u003c/a\u003e [nat\\_gateway\\_enabled](#input\\_nat\\_gateway\\_enabled) | Set `true` to create NAT Gateways to perform IPv4 NAT and NAT64 as needed.\u003cbr/\u003eDefaults to `true` unless `nat_instance_enabled` is `true`. | `bool` | `null` | no |\n| \u003ca name=\"input_nat_gateway_public_subnet_indices\"\u003e\u003c/a\u003e [nat\\_gateway\\_public\\_subnet\\_indices](#input\\_nat\\_gateway\\_public\\_subnet\\_indices) | The index (starting from 0) of the public subnet in each AZ to place the NAT Gateway.\u003cbr/\u003eIf you have multiple public subnets per AZ (via `public_subnets_per_az_count`), this determines which one gets the NAT Gateway.\u003cbr/\u003eDefault: `[0]` (use the first public subnet in each AZ).\u003cbr/\u003eYou can specify multiple indices if you want redundant NATs within an AZ, but this is rarely needed and increases cost.\u003cbr/\u003eCannot be used together with `nat_gateway_public_subnet_names`.\u003cbr/\u003eExample: `[0]` creates 1 NAT per AZ in the first public subnet.\u003cbr/\u003eExample: `[0, 1]` creates 2 NATs per AZ in the first and second public subnets (expensive). | `list(number)` | \u003cpre\u003e[\u003cbr/\u003e  0\u003cbr/\u003e]\u003c/pre\u003e | no |\n| \u003ca name=\"input_nat_gateway_public_subnet_names\"\u003e\u003c/a\u003e [nat\\_gateway\\_public\\_subnet\\_names](#input\\_nat\\_gateway\\_public\\_subnet\\_names) | The names of the public subnets in each AZ where NAT Gateways should be placed.\u003cbr/\u003eUses the names from `public_subnets_per_az_names` to determine placement.\u003cbr/\u003eThis is more intuitive than using indices - specify the subnet by name instead of position.\u003cbr/\u003eCannot be used together with `nat_gateway_public_subnet_indices` (only use indices OR names, not both).\u003cbr/\u003eIf not specified, defaults to using `nat_gateway_public_subnet_indices`.\u003cbr/\u003eExample: `[\"loadbalancer\"]` creates 1 NAT per AZ in the \"loadbalancer\" subnet.\u003cbr/\u003eExample: `[\"loadbalancer\", \"web\"]` creates 2 NATs per AZ in \"loadbalancer\" and \"web\" subnets (expensive). | `list(string)` | `null` | no |\n| \u003ca name=\"input_nat_instance_ami_id\"\u003e\u003c/a\u003e [nat\\_instance\\_ami\\_id](#input\\_nat\\_instance\\_ami\\_id) | A list optionally containing the ID of the AMI to use for the NAT instance.\u003cbr/\u003eIf the list is empty (the default), the latest official AWS NAT instance AMI\u003cbr/\u003ewill be used. NOTE: The Official NAT instance AMI is being phased out and\u003cbr/\u003edoes not support NAT64. Use of a NAT gateway is recommended instead. | `list(string)` | `[]` | no |\n| \u003ca name=\"input_nat_instance_cpu_credits_override\"\u003e\u003c/a\u003e [nat\\_instance\\_cpu\\_credits\\_override](#input\\_nat\\_instance\\_cpu\\_credits\\_override) | NAT Instance credit option for CPU usage. Valid values are \"standard\" or \"unlimited\".\u003cbr/\u003eT3 and later instances are launched as unlimited by default. T2 instances are launched as standard by default. | `string` | `\"\"` | no |\n| \u003ca name=\"input_nat_instance_enabled\"\u003e\u003c/a\u003e [nat\\_instance\\_enabled](#input\\_nat\\_instance\\_enabled) | Set `true` to create NAT Instances to perform IPv4 NAT.\u003cbr/\u003eDefaults to `false`. | `bool` | `null` | no |\n| \u003ca name=\"input_nat_instance_root_block_device_encrypted\"\u003e\u003c/a\u003e [nat\\_instance\\_root\\_block\\_device\\_encrypted](#input\\_nat\\_instance\\_root\\_block\\_device\\_encrypted) | Whether to encrypt the root block device on the created NAT instances | `bool` | `true` | no |\n| \u003ca name=\"input_nat_instance_type\"\u003e\u003c/a\u003e [nat\\_instance\\_type](#input\\_nat\\_instance\\_type) | NAT Instance type | `string` | `\"t3.micro\"` | no |\n| \u003ca name=\"input_open_network_acl_ipv4_rule_number\"\u003e\u003c/a\u003e [open\\_network\\_acl\\_ipv4\\_rule\\_number](#input\\_open\\_network\\_acl\\_ipv4\\_rule\\_number) | The `rule_no` assigned to the network ACL rules for IPv4 traffic generated by this module | `number` | `100` | no |\n| \u003ca name=\"input_open_network_acl_ipv6_rule_number\"\u003e\u003c/a\u003e [open\\_network\\_acl\\_ipv6\\_rule\\_number](#input\\_open\\_network\\_acl\\_ipv6\\_rule\\_number) | The `rule_no` assigned to the network ACL rules for IPv6 traffic generated by this module | `number` | `111` | no |\n| \u003ca name=\"input_private_assign_ipv6_address_on_creation\"\u003e\u003c/a\u003e [private\\_assign\\_ipv6\\_address\\_on\\_creation](#input\\_private\\_assign\\_ipv6\\_address\\_on\\_creation) | If `true`, network interfaces created in a private subnet will be assigned an IPv6 address | `bool` | `true` | no |\n| \u003ca name=\"input_private_dns64_nat64_enabled\"\u003e\u003c/a\u003e [private\\_dns64\\_nat64\\_enabled](#input\\_private\\_dns64\\_nat64\\_enabled) | If `true` and IPv6 is enabled, DNS queries made to the Amazon-provided DNS Resolver in private subnets will return synthetic\u003cbr/\u003eIPv6 addresses for IPv4-only destinations, and these addresses will be routed to the NAT Gateway.\u003cbr/\u003eRequires `public_subnets_enabled`, `nat_gateway_enabled`, and `private_route_table_enabled` to be `true` to be fully operational.\u003cbr/\u003eDefaults to `true` unless there is no public IPv4 subnet for egress, in which case it defaults to `false`. | `bool` | `null` | no |\n| \u003ca name=\"input_private_label\"\u003e\u003c/a\u003e [private\\_label](#input\\_private\\_label) | The string to use in IDs and elsewhere to identify resources for the private subnets and distinguish them from resources for the public subnets | `string` | `\"private\"` | no |\n| \u003ca name=\"input_private_open_network_acl_enabled\"\u003e\u003c/a\u003e [private\\_open\\_network\\_acl\\_enabled](#input\\_private\\_open\\_network\\_acl\\_enabled) | If `true`, a single network ACL be created and it will be associated with every private subnet, and a rule (number 100)\u003cbr/\u003ewill be created allowing all ingress and all egress. You can add additional rules to this network ACL\u003cbr/\u003eusing the `aws_network_acl_rule` resource.\u003cbr/\u003eIf `false`, you will need to manage the network ACL outside of this module. | `bool` | `true` | no |\n| \u003ca name=\"input_private_route_table_enabled\"\u003e\u003c/a\u003e [private\\_route\\_table\\_enabled](#input\\_private\\_route\\_table\\_enabled) | If `true`, a network route table and default route to the NAT gateway, NAT instance, or egress-only gateway\u003cbr/\u003ewill be created for each private subnet (1:1). If false, you will need to create your own route table(s) and route(s). | `bool` | `true` | no |\n| \u003ca name=\"input_private_subnets_additional_tags\"\u003e\u003c/a\u003e [private\\_subnets\\_additional\\_tags](#input\\_private\\_subnets\\_additional\\_tags) | Additional tags to be added to private subnets | `map(string)` | `{}` | no |\n| \u003ca name=\"input_private_subnets_enabled\"\u003e\u003c/a\u003e [private\\_subnets\\_enabled](#input\\_private\\_subnets\\_enabled) | If false, do not create private subnets (or NAT gateways or instances) | `bool` | `true` | no |\n| \u003ca name=\"input_private_subnets_per_az_count\"\u003e\u003c/a\u003e [private\\_subnets\\_per\\_az\\_count](#input\\_private\\_subnets\\_per\\_az\\_count) | The number of private subnets to provision per Availability Zone.\u003cbr/\u003eIf not provided, defaults to the value of `subnets_per_az_count` for backward compatibility.\u003cbr/\u003eSet this to create a different number of private subnets than public subnets. | `number` | `null` | no |\n| \u003ca name=\"input_private_subnets_per_az_names\"\u003e\u003c/a\u003e [private\\_subnets\\_per\\_az\\_names](#input\\_private\\_subnets\\_per\\_az\\_names) | The names to assign to the private subnets per Availability Zone.\u003cbr/\u003eIf not provided, defaults to the value of `subnets_per_az_names` for backward compatibility.\u003cbr/\u003eIf provided, the length must match `private_subnets_per_az_count`.\u003cbr/\u003eThe names will be used as keys in the outputs `named_private_subnets_map` and `named_private_route_table_ids_map`. | `list(string)` | `null` | no |\n| \u003ca name=\"input_public_assign_ipv6_address_on_creation\"\u003e\u003c/a\u003e [public\\_assign\\_ipv6\\_address\\_on\\_creation](#input\\_public\\_assign\\_ipv6\\_address\\_on\\_creation) | If `true`, network interfaces created in a public subnet will be assigned an IPv6 address | `bool` | `true` | no |\n| \u003ca name=\"input_public_dns64_nat64_enabled\"\u003e\u003c/a\u003e [public\\_dns64\\_nat64\\_enabled](#input\\_public\\_dns64\\_nat64\\_enabled) | If `true` and IPv6 is enabled, DNS queries made to the Amazon-provided DNS Resolver in public subnets will return synthetic\u003cbr/\u003eIPv6 addresses for IPv4-only destinations, and these addresses will be routed to the NAT Gateway.\u003cbr/\u003eRequires `nat_gateway_enabled` and `public_route_table_enabled` to be `true` to be fully operational. | `bool` | `false` | no |\n| \u003ca name=\"input_public_label\"\u003e\u003c/a\u003e [public\\_label](#input\\_public\\_label) | The string to use in IDs and elsewhere to identify resources for the public subnets and distinguish them from resources for the private subnets | `string` | `\"public\"` | no |\n| \u003ca name=\"input_public_open_network_acl_enabled\"\u003e\u003c/a\u003e [public\\_open\\_network\\_acl\\_enabled](#input\\_public\\_open\\_network\\_acl\\_enabled) | If `true`, a single network ACL be created and it will be associated with every public subnet, and a rule\u003cbr/\u003ewill be created allowing all ingress and all egress. You can add additional rules to this network ACL\u003cbr/\u003eusing the `aws_network_acl_rule` resource.\u003cbr/\u003eIf `false`, you will need to manage the network ACL outside of this module. | `bool` | `true` | no |\n| \u003ca name=\"input_public_route_table_enabled\"\u003e\u003c/a\u003e [public\\_route\\_table\\_enabled](#input\\_public\\_route\\_table\\_enabled) | If `true`, network route table(s) will be created as determined by `public_route_table_per_subnet_enabled` and\u003cbr/\u003eappropriate routes will be added to destinations this module knows about.\u003cbr/\u003eIf `false`, you will need to create your own route table(s) and route(s).\u003cbr/\u003eIgnored if `public_route_table_ids` is non-empty. | `bool` | `true` | no |\n| \u003ca name=\"input_public_route_table_ids\"\u003e\u003c/a\u003e [public\\_route\\_table\\_ids](#input\\_public\\_route\\_table\\_ids) | List optionally containing the ID of a single route table shared by all public subnets\u003cbr/\u003eor exactly one route table ID for each public subnet.\u003cbr/\u003eIf provided, it overrides `public_route_table_per_subnet_enabled`.\u003cbr/\u003eIf omitted and `public_route_table_enabled` is `true`,\u003cbr/\u003eone or more network route tables will be created for the public subnets,\u003cbr/\u003eaccording to the setting of `public_route_table_per_subnet_enabled`. | `list(string)` | `[]` | no |\n| \u003ca name=\"input_public_route_table_per_subnet_enabled\"\u003e\u003c/a\u003e [public\\_route\\_table\\_per\\_subnet\\_enabled](#input\\_public\\_route\\_table\\_per\\_subnet\\_enabled) | If `true` (and `public_route_table_enabled` is `true`), a separate network route table will be created for and associated with each public subnet.\u003cbr/\u003eIf `false` (and `public_route_table_enabled` is `true`), a single network route table will be created and it will be associated with every public subnet.\u003cbr/\u003eIf not set, it will be set to the value of `public_dns64_nat64_enabled`. | `bool` | `null` | no |\n| \u003ca name=\"input_public_subnets_additional_tags\"\u003e\u003c/a\u003e [public\\_subnets\\_additional\\_tags](#input\\_public\\_subnets\\_additional\\_tags) | Additional tags to be added to public subnets | `map(string)` | `{}` | no |\n| \u003ca name=\"input_public_subnets_enabled\"\u003e\u003c/a\u003e [public\\_subnets\\_enabled](#input\\_public\\_subnets\\_enabled) | If false, do not create public subnets.\u003cbr/\u003eSince NAT gateways and instances must be created in public subnets, these will also not be created when `false`. | `bool` | `true` | no |\n| \u003ca name=\"input_public_subnets_per_az_count\"\u003e\u003c/a\u003e [public\\_subnets\\_per\\_az\\_count](#input\\_public\\_subnets\\_per\\_az\\_count) | The number of public subnets to provision per Availability Zone.\u003cbr/\u003eIf not provided, defaults to the value of `subnets_per_az_count` for backward compatibility.\u003cbr/\u003eSet this to create a different number of public subnets than private subnets. | `number` | `null` | no |\n| \u003ca name=\"input_public_subnets_per_az_names\"\u003e\u003c/a\u003e [public\\_subnets\\_per\\_az\\_names](#input\\_public\\_subnets\\_per\\_az\\_names) | The names to assign to the public subnets per Availability Zone.\u003cbr/\u003eIf not provided, defaults to the value of `subnets_per_az_names` for backward compatibility.\u003cbr/\u003eIf provided, the length must match `public_subnets_per_az_count`.\u003cbr/\u003eThe names will be used as keys in the outputs `named_public_subnets_map` and `named_public_route_table_ids_map`. | `list(string)` | `null` | no |\n| \u003ca name=\"input_regex_replace_chars\"\u003e\u003c/a\u003e [regex\\_replace\\_chars](#input\\_regex\\_replace\\_chars) | Terraform regular expression (regex) string.\u003cbr/\u003eCharacters matching the regex will be removed from the ID elements.\u003cbr/\u003eIf not set, `\"/[^a-zA-Z0-9-]/\"` is used to remove all characters other than hyphens, letters and digits. | `string` | `null` | no |\n| \u003ca name=\"input_root_block_device_encrypted\"\u003e\u003c/a\u003e [root\\_block\\_device\\_encrypted](#input\\_root\\_block\\_device\\_encrypted) | DEPRECATED: use `nat_instance_root_block_device_encrypted` instead.\u003cbr/\u003eWhether to encrypt the root block device on the created NAT instances | `bool` | `null` | no |\n| \u003ca name=\"input_route_create_timeout\"\u003e\u003c/a\u003e [route\\_create\\_timeout](#input\\_route\\_create\\_timeout) | Time to wait for a network routing table entry to be created, specified as a Go Duration, e.g. `2m`. Use `null` for proivder default. | `string` | `null` | no |\n| \u003ca name=\"input_route_delete_timeout\"\u003e\u003c/a\u003e [route\\_delete\\_timeout](#input\\_route\\_delete\\_timeout) | Time to wait for a network routing table entry to be deleted, specified as a Go Duration, e.g. `2m`. Use `null` for proivder default. | `string` | `null` | no |\n| \u003ca name=\"input_stage\"\u003e\u003c/a\u003e [stage](#input\\_stage) | ID element. Usually used to indicate role, e.g. 'prod', 'staging', 'source', 'build', 'test', 'deploy', 'release' | `string` | `null` | no |\n| \u003ca name=\"input_subnet_create_timeout\"\u003e\u003c/a\u003e [subnet\\_create\\_timeout](#input\\_subnet\\_create\\_timeout) | Time to wait for a subnet to be created, specified as a Go Duration, e.g. `2m`. Use `null` for proivder default. | `string` | `null` | no |\n| \u003ca name=\"input_subnet_delete_timeout\"\u003e\u003c/a\u003e [subnet\\_delete\\_timeout](#input\\_subnet\\_delete\\_timeout) | Time to wait for a subnet to be deleted, specified as a Go Duration, e.g. `5m`. Use `null` for proivder default. | `string` | `null` | no |\n| \u003ca name=\"input_subnet_type_tag_key\"\u003e\u003c/a\u003e [subnet\\_type\\_tag\\_key](#input\\_subnet\\_type\\_tag\\_key) | DEPRECATED: Use `public_subnets_additional_tags` and `private_subnets_additional_tags` instead\u003cbr/\u003eKey for subnet type tag to provide information about the type of subnets, e.g. `cpco.io/subnet/type: private` or `cpco.io/subnet/type: public` | `string` | `null` | no |\n| \u003ca name=\"input_subnet_type_tag_value_format\"\u003e\u003c/a\u003e [subnet\\_type\\_tag\\_value\\_format](#input\\_subnet\\_type\\_tag\\_value\\_format) | DEPRECATED: Use `public_subnets_additional_tags` and `private_subnets_additional_tags` instead.\u003cbr/\u003eThe value of the `subnet_type_tag_key` will be set to `format(var.subnet_type_tag_value_format, \u003ctype\u003e)`\u003cbr/\u003ewhere `\u003ctype\u003e` is either `public` or `private`. | `string` | `\"%s\"` | no |\n| \u003ca name=\"input_subnets_per_az_count\"\u003e\u003c/a\u003e [subnets\\_per\\_az\\_count](#input\\_subnets\\_per\\_az\\_count) | The number of subnet of each type (public or private) to provision per Availability Zone. | `number` | `1` | no |\n| \u003ca name=\"input_subnets_per_az_names\"\u003e\u003c/a\u003e [subnets\\_per\\_az\\_names](#input\\_subnets\\_per\\_az\\_names) | The subnet names of each type (public or private) to provision per Availability Zone.\u003cbr/\u003eThis variable is optional.\u003cbr/\u003eIf a list of names is provided, the list items will be used as keys in the outputs `named_private_subnets_map`, `named_public_subnets_map`,\u003cbr/\u003e`named_private_route_table_ids_map` and `named_public_route_table_ids_map` | `list(string)` | \u003cpre\u003e[\u003cbr/\u003e  \"common\"\u003cbr/\u003e]\u003c/pre\u003e | no |\n| \u003ca name=\"input_tags\"\u003e\u003c/a\u003e [tags](#input\\_tags) | Additional tags (e.g. `{'BusinessUnit': 'XYZ'}`).\u003cbr/\u003eNeither the tag keys nor the tag values will be modified by this module. | `map(string)` | `{}` | no |\n| \u003ca name=\"input_tenant\"\u003e\u003c/a\u003e [tenant](#input\\_tenant) | ID element \\_(Rarely used, not included by default)\\_. A customer identifier, indicating who this instance of a resource is for | `string` | `null` | no |\n| \u003ca name=\"input_vpc_id\"\u003e\u003c/a\u003e [vpc\\_id](#input\\_vpc\\_id) | VPC ID where subnets will be created (e.g. `vpc-aceb2723`) | `string` | n/a | yes |\n\n## Outputs\n\n| Name | Description |\n|------|-------------|\n| \u003ca name=\"output_availability_zone_ids\"\u003e\u003c/a\u003e [availability\\_zone\\_ids](#output\\_availability\\_zone\\_ids) | List of Availability Zones IDs where subnets were created, when available |\n| \u003ca name=\"output_availability_zones\"\u003e\u003c/a\u003e [availability\\_zones](#output\\_availability\\_zones) | List of Availability Zones where subnets were created |\n| \u003ca name=\"output_az_private_route_table_ids_map\"\u003e\u003c/a\u003e [az\\_private\\_route\\_table\\_ids\\_map](#output\\_az\\_private\\_route\\_table\\_ids\\_map) | Map of AZ names to list of private route table IDs in the AZs |\n| \u003ca name=\"output_az_private_subnets_map\"\u003e\u003c/a\u003e [az\\_private\\_subnets\\_map](#output\\_az\\_private\\_subnets\\_map) | Map of AZ names to list of private subnet IDs in the AZs |\n| \u003ca name=\"output_az_public_route_table_ids_map\"\u003e\u003c/a\u003e [az\\_public\\_route\\_table\\_ids\\_map](#output\\_az\\_public\\_route\\_table\\_ids\\_map) | Map of AZ names to list of public route table IDs in the AZs |\n| \u003ca name=\"output_az_public_subnets_map\"\u003e\u003c/a\u003e [az\\_public\\_subnets\\_map](#output\\_az\\_public\\_subnets\\_map) | Map of AZ names to list of public subnet IDs in the AZs |\n| \u003ca name=\"output_named_private_route_table_ids_map\"\u003e\u003c/a\u003e [named\\_private\\_route\\_table\\_ids\\_map](#output\\_named\\_private\\_route\\_table\\_ids\\_map) | Map of subnet names (specified in `private_subnets_per_az_names` or `subnets_per_az_names` variable) to lists of private route table IDs |\n| \u003ca name=\"output_named_private_subnets_map\"\u003e\u003c/a\u003e [named\\_private\\_subnets\\_map](#output\\_named\\_private\\_subnets\\_map) | Map of subnet names (specified in `private_subnets_per_az_names` or `subnets_per_az_names` variable) to lists of private subnet IDs |\n| \u003ca name=\"output_named_private_subnets_stats_map\"\u003e\u003c/a\u003e [named\\_private\\_subnets\\_stats\\_map](#output\\_named\\_private\\_subnets\\_stats\\_map) | Map of subnet names (specified in `private_subnets_per_az_names` or `subnets_per_az_names` variable) to lists of objects with each object having four items: AZ, private subnet ID, private route table ID, NAT Gateway ID (the NAT Gateway that this private subnet routes to for egress) |\n| \u003ca name=\"output_named_public_route_table_ids_map\"\u003e\u003c/a\u003e [named\\_public\\_route\\_table\\_ids\\_map](#output\\_named\\_public\\_route\\_table\\_ids\\_map) | Map of subnet names (specified in `public_subnets_per_az_names` or `subnets_per_az_names` variable) to lists of public route table IDs |\n| \u003ca name=\"output_named_public_subnets_map\"\u003e\u003c/a\u003e [named\\_public\\_subnets\\_map](#output\\_named\\_public\\_subnets\\_map) | Map of subnet names (specified in `public_subnets_per_az_names` or `subnets_per_az_names` variable) to lists of public subnet IDs |\n| \u003ca name=\"output_named_public_subnets_stats_map\"\u003e\u003c/a\u003e [named\\_public\\_subnets\\_stats\\_map](#output\\_named\\_public\\_subnets\\_stats\\_map) | Map of subnet names (specified in `public_subnets_per_az_names` or `subnets_per_az_names` variable) to lists of objects with each object having four items: AZ, public subnet ID, public route table ID, NAT Gateway ID (the NAT Gateway in this public subnet, if any) |\n| \u003ca name=\"output_nat_eip_allocation_ids\"\u003e\u003c/a\u003e [nat\\_eip\\_allocation\\_ids](#output\\_nat\\_eip\\_allocation\\_ids) | Elastic IP allocations in use by NAT |\n| \u003ca name=\"output_nat_gateway_ids\"\u003e\u003c/a\u003e [nat\\_gateway\\_ids](#output\\_nat\\_gateway\\_ids) | IDs of the NAT Gateways created |\n| \u003ca name=\"output_nat_gateway_private_ips\"\u003e\u003c/a\u003e [nat\\_gateway\\_private\\_ips](#output\\_nat\\_gateway\\_private\\_ips) | Private IP addresses of the NAT Gateways |\n| \u003ca name=\"output_nat_gateway_public_ips\"\u003e\u003c/a\u003e [nat\\_gateway\\_public\\_ips](#output\\_nat\\_gateway\\_public\\_ips) | DEPRECATED: use `nat_ips` instead. Public IPv4 IP addresses in use by NAT. |\n| \u003ca name=\"output_nat_instance_ami_id\"\u003e\u003c/a\u003e [nat\\_instance\\_ami\\_id](#output\\_nat\\_instance\\_ami\\_id) | ID of AMI used by NAT instance |\n| \u003ca name=\"output_nat_instance_ids\"\u003e\u003c/a\u003e [nat\\_instance\\_ids](#output\\_nat\\_instance\\_ids) | IDs of the NAT Instances created |\n| \u003ca name=\"output_nat_ips\"\u003e\u003c/a\u003e [nat\\_ips](#output\\_nat\\_ips) | Elastic IP Addresses in use by NAT |\n| \u003ca name=\"output_private_network_acl_id\"\u003e\u003c/a\u003e [private\\_network\\_acl\\_id](#output\\_private\\_network\\_acl\\_id) | ID of the Network ACL created for private subnets |\n| \u003ca name=\"output_private_route_table_ids\"\u003e\u003c/a\u003e [private\\_route\\_table\\_ids](#output\\_private\\_route\\_table\\_ids) | IDs of the created private route tables |\n| \u003ca name=\"output_private_subnet_arns\"\u003e\u003c/a\u003e [private\\_subnet\\_arns](#output\\_private\\_subnet\\_arns) | ARNs of the created private subnets |\n| \u003ca name=\"output_private_subnet_cidrs\"\u003e\u003c/a\u003e [private\\_subnet\\_cidrs](#output\\_private\\_subnet\\_cidrs) | IPv4 CIDR blocks of the created private subnets |\n| \u003ca name=\"output_private_subnet_ids\"\u003e\u003c/a\u003e [private\\_subnet\\_ids](#output\\_private\\_subnet\\_ids) | IDs of the created private subnets |\n| \u003ca name=\"output_private_subnet_ipv6_cidrs\"\u003e\u003c/a\u003e [private\\_subnet\\_ipv6\\_cidrs](#output\\_private\\_subnet\\_ipv6\\_cidrs) | IPv6 CIDR blocks of the created private subnets |\n| \u003ca name=\"output_public_network_acl_id\"\u003e\u003c/a\u003e [public\\_network\\_acl\\_id](#output\\_public\\_network\\_acl\\_id) | ID of the Network ACL created for public subnets |\n| \u003ca name=\"output_public_route_table_ids\"\u003e\u003c/a\u003e [public\\_route\\_table\\_ids](#output\\_public\\_route\\_table\\_ids) | IDs of the created public route tables |\n| \u003ca name=\"output_public_subnet_arns\"\u003e\u003c/a\u003e [public\\_subnet\\_arns](#output\\_public\\_subnet\\_arns) | ARNs of the created public subnets |\n| \u003ca name=\"output_public_subnet_cidrs\"\u003e\u003c/a\u003e [public\\_subnet\\_cidrs](#output\\_public\\_subnet\\_cidrs) | IPv4 CIDR blocks of the created public subnets |\n| \u003ca name=\"output_public_subnet_ids\"\u003e\u003c/a\u003e [public\\_subnet\\_ids](#output\\_public\\_subnet\\_ids) | IDs of the created public subnets |\n| \u003ca name=\"output_public_subnet_ipv6_cidrs\"\u003e\u003c/a\u003e [public\\_subnet\\_ipv6\\_cidrs](#output\\_public\\_subnet\\_ipv6\\_cidrs) | IPv6 CIDR blocks of the created public subnets |\n\u003c!-- markdownlint-restore --\u003e\n\n\n\n\n\n## Subnet calculation logic\n\n`terraform-aws-dynamic-subnets` creates a set of subnets based on various CIDR inputs and \nthe maximum possible number of subnets, which is `max_subnet_count` when specified or\nthe number of Availability Zones in the region when `max_subnet_count` is left at \nits default value of zero.\n\nYou can explicitly provide CIDRs for subnets via `ipv4_cidrs` and `ipv6_cidrs` inputs if you want,\nbut the usual use case is to provide a single CIDR which this module will subdivide into a set\nof CIDRs as follows:\n\n1. Get number of available AZ in the region:\n```\nexisting_az_count = length(data.aws_availability_zones.available.names)\n```\n2. Determine how many sets of subnets are being created. (Usually it is `2`: `public` and `private`): `subnet_type_count`.\n3. Multiply the results of (1) and (2) to determine how many CIDRs to reserve:\n```\ncidr_count = existing_az_count * subnet_type_count\n```\n\n4. Calculate the number of bits needed to enumerate all the CIDRs:\n```\nsubnet_bits = ceil(log(cidr_count, 2))\n```\n5. Reserve CIDRs for private subnets using [`cidrsubnet`](https://www.terraform.io/language/functions/cidrsubnet): \n```\nprivate_subnet_cidrs = [ for netnumber in range(0, existing_az_count): cidrsubnet(cidr_block, subnet_bits, netnumber) ]\n```\n6. Reserve CIDRs for public subnets in the second half of the CIDR block:\n```\npublic_subnet_cidrs = [ for netnumber in range(existing_az_count, existing_az_count * 2): cidrsubnet(cidr_block, subnet_bits, netnumber) ]\n```\n\n\nNote that this means that, for example, in a region with 4 availability zones, if you specify only 3 availability zones \nin `var.availability_zones`, this module will still reserve CIDRs for the 4th zone. This is so that if you later\nwant to expand into that zone, the existing subnet CIDR assignments will not be disturbed. If you do not want\nto reserve these CIDRs, set `max_subnet_count` to the number of zones you are actually using.\n\n\n## Related Projects\n\nCheck out these related projects.\n\n- [terraform-aws-vpc](https://github.com/cloudposse/terraform-aws-vpc) - Terraform Module that defines a VPC with public/private subnets across multiple AZs with Internet Gateways\n- [terraform-aws-vpc-peering](https://github.com/cloudposse/terraform-aws-vpc-peering) - Terraform module to create a peering connection between two VPCs\n- [terraform-aws-kops-vpc-peering](https://github.com/cloudposse/terraform-aws-kops-vpc-peering) - Terraform module to create a peering connection between a backing services VPC and a VPC created by Kops\n- [terraform-aws-named-subnets](https://github.com/cloudposse/terraform-aws-named-subnets) - Terraform module for named subnets provisioning.\n\n\n\u003e [!TIP]\n\u003e #### Use Terraform Reference Architectures for AWS\n\u003e\n\u003e Use Cloud Posse's ready-to-go [terraform architecture blueprints](https://cloudposse.com/reference-architecture/) for AWS to get up and running quickly.\n\u003e\n\u003e ✅ We build it together with your team.\u003cbr/\u003e\n\u003e ✅ Your team owns everything.\u003cbr/\u003e\n\u003e ✅ 100% Open Source and backed by fanatical support.\u003cbr/\u003e\n\u003e\n\u003e \u003ca href=\"https://cpco.io/commercial-support?utm_source=github\u0026utm_medium=readme\u0026utm_campaign=cloudposse/terraform-aws-dynamic-subnets\u0026utm_content=commercial_support\"\u003e\u003cimg alt=\"Request Quote\" src=\"https://img.shields.io/badge/request%20quote-success.svg?style=for-the-badge\"/\u003e\u003c/a\u003e\n\u003e \u003cdetails\u003e\u003csummary\u003e📚 \u003cstrong\u003eLearn More\u003c/strong\u003e\u003c/summary\u003e\n\u003e\n\u003e \u003cbr/\u003e\n\u003e\n\u003e Cloud Posse is the leading [**DevOps Accelerator**](https://cpco.io/commercial-support?utm_source=github\u0026utm_medium=readme\u0026utm_campaign=cloudposse/terraform-aws-dynamic-subnets\u0026utm_content=commercial_support) for funded startups and enterprises.\n\u003e\n\u003e *Your team can operate like a pro today.*\n\u003e\n\u003e Ensure that your team succeeds by using Cloud Posse's proven process and turnkey blueprints. Plus, we stick around until you succeed.\n\u003e #### Day-0:  Your Foundation for Success\n\u003e - **Reference Architecture.** You'll get everything you need from the ground up built using 100% infrastructure as code.\n\u003e - **Deployment Strategy.** Adopt a proven deployment strategy with GitHub Actions, enabling automated, repeatable, and reliable software releases.\n\u003e - **Site Reliability Engineering.** Gain total visibility into your applications and services with Datadog, ensuring high availability and performance.\n\u003e - **Security Baseline.** Establish a secure environment from the start, with built-in governance, accountability, and comprehensive audit logs, safeguarding your operations.\n\u003e - **GitOps.** Empower your team to manage infrastructure changes confidently and efficiently through Pull Requests, leveraging the full power of GitHub Actions.\n\u003e\n\u003e \u003ca href=\"https://cpco.io/commercial-support?utm_source=github\u0026utm_medium=readme\u0026utm_campaign=cloudposse/terraform-aws-dynamic-subnets\u0026utm_content=commercial_support\"\u003e\u003cimg alt=\"Request Quote\" src=\"https://img.shields.io/badge/request%20quote-success.svg?style=for-the-badge\"/\u003e\u003c/a\u003e\n\u003e\n\u003e #### Day-2: Your Operational Mastery\n\u003e - **Training.** Equip your team with the knowledge and skills to confidently manage the infrastructure, ensuring long-term success and self-sufficiency.\n\u003e - **Support.** Benefit from a seamless communication over Slack with our experts, ensuring you have the support you need, whenever you need it.\n\u003e - **Troubleshooting.** Access expert assistance to quickly resolve any operational challenges, minimizing downtime and maintaining business continuity.\n\u003e - **Code Reviews.** Enhance your team’s code quality with our expert feedback, fostering continuous improvement and collaboration.\n\u003e - **Bug Fixes.** Rely on our team to troubleshoot and resolve any issues, ensuring your systems run smoothly.\n\u003e - **Migration Assistance.** Accelerate your migration process with our dedicated support, minimizing disruption and speeding up time-to-value.\n\u003e - **Customer Workshops.** Engage with our team in weekly workshops, gaining insights and strategies to continuously improve and innovate.\n\u003e\n\u003e \u003ca href=\"https://cpco.io/commercial-support?utm_source=github\u0026utm_medium=readme\u0026utm_campaign=cloudposse/terraform-aws-dynamic-subnets\u0026utm_content=commercial_support\"\u003e\u003cimg alt=\"Request Quote\" src=\"https://img.shields.io/badge/request%20quote-success.svg?style=for-the-badge\"/\u003e\u003c/a\u003e\n\u003e \n\u003c/details\u003e\n\n## ✨ Contributing\n\nThis project is under active development, and we encourage contributions from our community.\n\n\n\nMany thanks to our outstanding contributors:\n\n\u003ca href=\"https://github.com/cloudposse/terraform-aws-dynamic-subnets/graphs/contributors\"\u003e\n  \u003cimg src=\"https://contrib.rocks/image?repo=cloudposse/terraform-aws-dynamic-subnets\u0026max=24\" /\u003e\n\u003c/a\u003e\n\nFor 🐛 bug reports \u0026 feature requests, please use the [issue tracker](https://github.com/cloudposse/terraform-aws-dynamic-subnets/issues).\n\nIn general, PRs are welcome. We follow the typical \"fork-and-pull\" Git workflow.\n 1. Review our [Code of Conduct](https://github.com/cloudposse/terraform-aws-dynamic-subnets/?tab=coc-ov-file#code-of-conduct) and [Contributor Guidelines](https://github.com/cloudposse/.github/blob/main/CONTRIBUTING.md).\n 2. **Fork** the repo on GitHub\n 3. **Clone** the project to your own machine\n 4. **Commit** changes to your own branch\n 5. **Push** your work back up to your fork\n 6. Submit a **Pull Request** so that we can review your changes\n\n**NOTE:** Be sure to merge the latest changes from \"upstream\" before making a pull request!\n\n\n## Running Terraform Tests\n\nWe use [Atmos](https://atmos.tools) to streamline how Terraform tests are run. It centralizes configuration and wraps common test workflows with easy-to-use commands.\n\nAll tests are located in the [`test/`](test) folder.\n\nUnder the hood, tests are powered by Terratest together with our internal [Test Helpers](https://github.com/cloudposse/test-helpers) library, providing robust infrastructure validation.\n\nSetup dependencies:\n- Install Atmos ([installation guide](https://atmos.tools/install/))\n- Install Go [1.24+ or newer](https://go.dev/doc/install)\n- Install Terraform or OpenTofu\n\nTo run tests:\n\n- Run all tests:  \n  ```sh\n  atmos test run\n  ```\n- Clean up test artifacts:  \n  ```sh\n  atmos test clean\n  ```\n- Explore additional test options:  \n  ```sh\n  atmos test --help\n  ```\nThe configuration for test commands is centrally managed. To review what's being imported, see the [`atmos.yaml`](https://raw.githubusercontent.com/cloudposse/.github/refs/heads/main/.github/atmos/terraform-module.yaml) file.\n\nLearn more about our [automated testing in our documentation](https://docs.cloudposse.com/community/contribute/automated-testing/) or implementing [custom commands](https://atmos.tools/core-concepts/custom-commands/) with atmos.\n\n### 🌎 Slack Community\n\nJoin our [Open Source Community](https://cpco.io/slack?utm_source=github\u0026utm_medium=readme\u0026utm_campaign=cloudposse/terraform-aws-dynamic-subnets\u0026utm_content=slack) on Slack. It's **FREE** for everyone! Our \"SweetOps\" community is where you get to talk with others who share a similar vision for how to rollout and manage infrastructure. This is the best place to talk shop, ask questions, solicit feedback, and work together as a community to build totally *sweet* infrastructure.\n\n### 📰 Newsletter\n\nSign up for [our newsletter](https://cpco.io/newsletter?utm_source=github\u0026utm_medium=readme\u0026utm_campaign=cloudposse/terraform-aws-dynamic-subnets\u0026utm_content=newsletter) and join 3,000+ DevOps engineers, CTOs, and founders who get insider access to the latest DevOps trends, so you can always stay in the know.\nDropped straight into your Inbox every week — and usually a 5-minute read.\n\n### 📆 Office Hours \u003ca href=\"https://cloudposse.com/office-hours?utm_source=github\u0026utm_medium=readme\u0026utm_campaign=cloudposse/terraform-aws-dynamic-subnets\u0026utm_content=office_hours\"\u003e\u003cimg src=\"https://img.cloudposse.com/fit-in/200x200/https://cloudposse.com/wp-content/uploads/2019/08/Powered-by-Zoom.png\" align=\"right\" /\u003e\u003c/a\u003e\n\n[Join us every Wednesday via Zoom](https://cloudposse.com/office-hours?utm_source=github\u0026utm_medium=readme\u0026utm_campaign=cloudposse/terraform-aws-dynamic-subnets\u0026utm_content=office_hours) for your weekly dose of insider DevOps trends, AWS news and Terraform insights, all sourced from our SweetOps community, plus a _live Q\u0026A_ that you can’t find anywhere else.\nIt's **FREE** for everyone!\n## License\n\n\u003ca href=\"https://opensource.org/licenses/Apache-2.0\"\u003e\u003cimg src=\"https://img.shields.io/badge/License-Apache%202.0-blue.svg?style=for-the-badge\" alt=\"License\"\u003e\u003c/a\u003e\n\n\u003cdetails\u003e\n\u003csummary\u003ePreamble to the Apache License, Version 2.0\u003c/summary\u003e\n\u003cbr/\u003e\n\u003cbr/\u003e\n\nComplete license is available in the [`LICENSE`](LICENSE) file.\n\n```text\nLicensed to the Apache Software Foundation (ASF) under one\nor more contributor license agreements.  See the NOTICE file\ndistributed with this work for additional information\nregarding copyright ownership.  The ASF licenses this file\nto you under the Apache License, Version 2.0 (the\n\"License\"); you may not use this file except in compliance\nwith the License.  You may obtain a copy of the License at\n\n  https://www.apache.org/licenses/LICENSE-2.0\n\nUnless required by applicable law or agreed to in writing,\nsoftware distributed under the License is distributed on an\n\"AS IS\" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY\nKIND, either express or implied.  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