GitHub - cloudposse-terraform-components/aws-tgw-hub: This component is responsible for provisioning an AWS Transit Gateway hub that acts as a centralized gateway for connecting VPCs from other spoke accounts

This component is responsible for provisioning an AWS Transit Gateway hub that acts as a centralized gateway for connecting VPCs from other spoke accounts.

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Usage

Stack Level: Regional

Basic Usage with `tgw/spoke`

Here's an example snippet for how to configure and use this component:

components:
  terraform:
    tgw/hub/defaults:
      metadata:
        type: abstract
        component: tgw/hub
      vars:
        enabled: true
        name: tgw-hub
        expose_eks_sg: false
        tags:
          Team: sre
          Service: tgw-hub

    tgw/hub:
      metadata:
        inherits:
          - tgw/hub/defaults
        component: tgw/hub
      vars:
        connections:
          - account:
              tenant: core
              stage: network
            vpc_component_names:
              - vpc-dev
          - account:
              tenant: core
              stage: artifacts
          - account:
              tenant: core
              stage: auto
            eks_component_names:
              - eks/cluster
          - account:
              tenant: plat
              stage: dev
            vpc_component_names:
              - vpc
              - vpc/data/1
            eks_component_names:
              - eks/cluster
          - account:
              tenant: plat
              stage: staging
            vpc_component_names:
              - vpc
              - vpc/data/1
            eks_component_names:
              - eks/cluster
          - account:
              tenant: plat
              stage: prod
            vpc_component_names:
              - vpc
              - vpc/data/1
            eks_component_names:
              - eks/cluster

To provision the Transit Gateway and all related resources, run the following commands:

atmos terraform plan tgw/hub -s <tenant>-<environment>-network
atmos terraform apply tgw/hub -s <tenant>-<environment>-network

Alternate Usage with `tgw/attachment`, `tgw/routes`, and `vpc/routes`

Components Overview

tgw/hub: Creates the Transit Gateway in the network account
tgw/attachment: Creates and manages Transit Gateway VPC attachments in connected accounts
tgw/hub-connection: Creates the Transit Gateway peering connection between two tgw/hub deployments
tgw/routes: Manages Transit Gateway route tables in the network account
vpc-routes (vpc/routes/private): Configures VPC route tables in connected accounts to route traffic through the Transit Gateway (Note: This component lives outside the tgw/ directory since it's not specific to Transit Gateway)

Architecture

The Transit Gateway components work together in the following way:

Transit Gateway is created in the network account (tgw/hub)
VPCs in other accounts attach to the Transit Gateway (tgw/attachment)
Route tables in connected VPCs direct traffic across accounts (vpc-routes)
Transit Gateway route tables control routing between attachments (tgw/routes)

graph TD
    subgraph core-use1-network
        TGW[Transit Gateway]
        TGW_RT[TGW Route Tables]
    end

    subgraph plat-use1-dev
        VPC1[VPC]
        VPC1_RT[VPC Route Tables]
        ATT1[TGW Attachment]
    end

    subgraph core-use1-auto
        VPC2[VPC]
        VPC2_RT[VPC Route Tables]
        ATT2[TGW Attachment]
    end

    ATT1 <--> TGW
    ATT2 <--> TGW
    TGW <--> TGW_RT
    VPC1_RT <--> VPC1
    VPC2_RT <--> VPC2
    VPC1 <--> ATT1
    VPC2 <--> ATT2

Deployment Steps

1. Deploy Transit Gateway Hub

First, create the Transit Gateway in the network account.

Tip

Leave var.connections empty. With this refactor, the tgw/hub component is only responsible for creating the Transit Gateway and its route tables. We do not need to fetch and store outputs for the connected components anymore.

components:
  terraform:
    tgw/hub:
      vars:
        connections: []

2. Deploy VPC Attachments

Important: Deploy attachments in connected accounts first, before deploying attachments in the network account.

Connected Account Attachments

components:
  terraform:
    tgw/attachment:
      vars:
        transit_gateway_id: !terraform.output tgw/hub core-use1-network transit_gateway_id
        transit_gateway_route_table_id: !terraform.output tgw/hub core-use1-network transit_gateway_route_table_id
        create_transit_gateway_route_table_association: false

Network Account Attachment

components:
  terraform:
    tgw/attachment:
      vars:
        transit_gateway_id: !terraform.output tgw/hub core-use1-network transit_gateway_id
        transit_gateway_route_table_id: !terraform.output tgw/hub core-use1-network transit_gateway_route_table_id

        # Route table associations are required so that route tables can propagate their routes to other route tables.
        # Set the following to true in the same account where the Transit Gateway and its route tables are deployed
        create_transit_gateway_route_table_association: true

        # Associate connected accounts with the Transit Gateway route table
        additional_associations:
          - attachment_id: !terraform.output tgw/attachment core-use1-auto transit_gateway_vpc_attachment_id
            route_table_id: !terraform.output tgw/hub transit_gateway_route_table_id
          - attachment_id: !terraform.output tgw/attachment plat-use1-dev transit_gateway_vpc_attachment_id
            route_table_id: !terraform.output tgw/hub transit_gateway_route_table_id

3. Configure VPC Routes

Configure routes in all connected VPCs.

components:
  terraform:
    vpc/routes/private:
      metadata:
        component: vpc-routes
      vars:
        route_table_ids: !terraform.output vpc private_route_table_ids
        routes:
          # Route to network account
          - destination:
              cidr_block: !terraform.output vpc core-use1-network vpc_cidr
            target:
              type: transit_gateway_id
              value: !terraform.output tgw/hub core-use1-network transit_gateway_id

          # Route to core-auto account, if necessary
          - destination:
              cidr_block: !terraform.output vpc core-use1-auto vpc_cidr
            target:
              type: transit_gateway_id
              value: !terraform.output tgw/hub core-use1-network transit_gateway_id

Configure routes in the Network Account VPCs.

components:
  terraform:
    vpc/routes/private:
      vars:
        route_table_ids: !terraform.output vpc private_route_table_ids
        routes:
          # Routes to connected accounts
          - destination:
              cidr_block: !terraform.output vpc core-use1-auto vpc_cidr
            target:
              type: transit_gateway_id
              value: !terraform.output tgw/hub transit_gateway_id
          - destination:
              cidr_block: !terraform.output vpc plat-use1-dev vpc_cidr
            target:
              type: transit_gateway_id
              value: !terraform.output tgw/hub transit_gateway_id

4. Deploy Transit Gateway Route Table Routes

Deploy the tgw/routes component in the network account to create route tables and routes.

components:
  terraform:
    tgw/routes:
      vars:
        transit_gateway_route_table_id: !terraform.output tgw/hub transit_gateway_route_table_id
        # Use propagated routes to route through VPC attachments
        propagated_routes:
          # Route to this account
          - attachment_id: !terraform.output tgw/attachment core-use1-network transit_gateway_attachment_id
          # Route to any connected account
          - attachment_id: !terraform.output tgw/attachment core-use1-auto transit_gateway_attachment_id
          - attachment_id: !terraform.output tgw/attachment plat-use1-dev transit_gateway_attachment_id

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.

Related Projects

Check out these related projects.

Cloud Posse Terraform Modules - Our collection of reusable Terraform modules used by our reference architectures.
Atmos - Atmos is like docker-compose but for your infrastructure

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License

Preamble to the Apache License, Version 2.0

Licensed to the Apache Software Foundation (ASF) under one
or more contributor license agreements.  See the NOTICE file
distributed with this work for additional information
regarding copyright ownership.  The ASF licenses this file
to you under the Apache License, Version 2.0 (the
"License"); you may not use this file except in compliance
with the License.  You may obtain a copy of the License at

  https://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing,
software distributed under the License is distributed on an
"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
KIND, either express or implied.  See the License for the
specific language governing permissions and limitations
under the License.

Trademarks

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

Requirements

Name	Version
terraform	>= 1.0.0
aws	>= 4.1

Providers

No providers.

Modules

Name	Source	Version
account_map	cloudposse/stack-config/yaml//modules/remote-state	1.5.0
eks	cloudposse/stack-config/yaml//modules/remote-state	1.5.0
iam_roles	../../account-map/modules/iam-roles	n/a
tgw_hub	cloudposse/transit-gateway/aws	0.11.0
this	cloudposse/label/null	0.25.0
vpc	cloudposse/stack-config/yaml//modules/remote-state	1.5.0

Resources

No resources.

Inputs

Name	Description	Type	Default	Required
account_map_environment_name	The name of the environment where `account_map` is provisioned	`string`	`"gbl"`	no
account_map_stage_name	The name of the stage where `account_map` is provisioned	`string`	`"root"`	no
account_map_tenant_name	The name of the tenant where `account_map` is provisioned. If the `tenant` label is not used, leave this as `null`.	`string`	`null`	no
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
allow_external_principals	Set true to allow the TGW to be RAM shared with external principals specified in ram_principals	`bool`	`false`	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
connections	A list of objects to define each TGW connections. By default, each connection will look for only the default `vpc` component.	list(object({ account = object({ stage = string environment = optional(string, "") tenant = optional(string, "") }) vpc_component_names = optional(list(string), ["vpc"]) eks_component_names = optional(list(string), []) }))	`[]`	no
context	Single object for setting entire context at once. See description of individual variables for details. Leave string and numeric variables as `null` to use default value. Individual variable settings (non-null) override settings in context object, except for attributes, tags, and additional_tag_map, which are merged.	`any`	{ "additional_tag_map": {}, "attributes": [], "delimiter": null, "descriptor_formats": {}, "enabled": true, "environment": null, "id_length_limit": null, "label_key_case": null, "label_order": [], "label_value_case": null, "labels_as_tags": [ "unset" ], "name": null, "namespace": null, "regex_replace_chars": null, "stage": null, "tags": {}, "tenant": null }	no
delimiter	Delimiter to be used between ID elements. Defaults to `-` (hyphen). Set to `""` to use no delimiter at all.	`string`	`null`	no
descriptor_formats	Describe additional descriptors to be output in the `descriptors` output map. Map of maps. Keys are names of descriptors. Values are maps of the form `{<br/> format = string<br/> labels = list(string)<br/>}` (Type is `any` so the map values can later be enhanced to provide additional options.) `format` is a Terraform format string to be passed to the `format()` function. `labels` is a list of labels, in order, to pass to `format()` function. Label values will be normalized before being passed to `format()` so they will be identical to how they appear in `id`. Default is `{}` (`descriptors` output will be empty).	`any`	`{}`	no
enabled	Set to false to prevent the module from creating any resources	`bool`	`null`	no
environment	ID element. Usually used for region e.g. 'uw2', 'us-west-2', OR role 'prod', 'staging', 'dev', 'UAT'	`string`	`null`	no
expose_eks_sg	Set true to allow EKS clusters to accept traffic from source accounts	`bool`	`true`	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
label_key_case	Controls the letter case of the `tags` keys (label names) for tags generated by this module. Does not affect keys of tags passed in via the `tags` input. Possible values: `lower`, `title`, `upper`. Default value: `title`.	`string`	`null`	no
label_order	The order in which the labels (ID elements) appear in the `id`. Defaults to ["namespace", "environment", "stage", "name", "attributes"]. You can omit any of the 6 labels ("tenant" is the 6th), but at least one must be present.	`list(string)`	`null`	no
label_value_case	Controls the letter case of ID elements (labels) as included in `id`, set as tag values, and output by this module individually. Does not affect values of tags passed in via the `tags` input. Possible values: `lower`, `title`, `upper` and `none` (no transformation). Set this to `title` and set `delimiter` to `""` to yield Pascal Case IDs. Default value: `lower`.	`string`	`null`	no
labels_as_tags	Set of labels (ID elements) to include as tags in the `tags` output. Default is to include all labels. Tags with empty values will not be included in the `tags` output. Set to `[]` to suppress all generated tags. Notes: The value of the `name` tag, if included, will be the `id`, not the `name`. Unlike other `null-label` inputs, the initial setting of `labels_as_tags` cannot be changed in later chained modules. Attempts to change it will be silently ignored.	`set(string)`	[ "default" ]	no
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
ram_principals	A list of AWS account IDs to share the TGW with outside the organization	`list(string)`	`[]`	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
region	AWS Region	`string`	n/a	yes
stage	ID element. Usually used to indicate role, e.g. 'prod', 'staging', 'source', 'build', 'test', 'deploy', 'release'	`string`	`null`	no
tags	Additional tags (e.g. `{'BusinessUnit': 'XYZ'}`). Neither the tag keys nor the tag values will be modified by this module.	`map(string)`	`{}`	no
tenant	ID element _(Rarely used, not included by default)_. A customer identifier, indicating who this instance of a resource is for	`string`	`null`	no

Outputs

Name	Description
eks	Accounts with EKS and EKSs information
tgw_config	Transit Gateway config
transit_gateway_arn	Transit Gateway ARN
transit_gateway_id	Transit Gateway ID
transit_gateway_route_table_id	Transit Gateway route table ID
vpcs	Accounts with VPC and VPCs information

Name		Name	Last commit message	Last commit date
Latest commit History 27 Commits
.github		.github
docs		docs
src		src
test		test
.editorconfig		.editorconfig
.gitattributes		.gitattributes
.gitignore		.gitignore
.pre-commit-config.yaml		.pre-commit-config.yaml
.tflint.hcl		.tflint.hcl
Makefile		Makefile
README.md		README.md
README.yaml		README.yaml
_typos.toml		_typos.toml

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👽 Use Atmos with Terraform

Usage

Basic Usage with `tgw/spoke`

Alternate Usage with `tgw/attachment`, `tgw/routes`, and `vpc/routes`

Components Overview

Architecture

Deployment Steps

1. Deploy Transit Gateway Hub

2. Deploy VPC Attachments

Connected Account Attachments

Network Account Attachment

3. Configure VPC Routes

4. Deploy Transit Gateway Route Table Routes

Related Projects

Use Terraform Reference Architectures for AWS

Day-0: Your Foundation for Success

Day-2: Your Operational Mastery

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👽 Use Atmos with Terraform

Usage

Basic Usage with tgw/spoke

Alternate Usage with tgw/attachment, tgw/routes, and vpc/routes

Components Overview

Architecture

Deployment Steps

1. Deploy Transit Gateway Hub

2. Deploy VPC Attachments

Connected Account Attachments

Network Account Attachment

3. Configure VPC Routes

4. Deploy Transit Gateway Route Table Routes

Related Projects

Use Terraform Reference Architectures for AWS

Day-0: Your Foundation for Success

Day-2: Your Operational Mastery

✨ Contributing

🌎 Slack Community

📰 Newsletter

📆 Office Hours

License

Trademarks

Requirements

Providers

Modules

Resources

Inputs

Outputs

About

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Basic Usage with `tgw/spoke`

Alternate Usage with `tgw/attachment`, `tgw/routes`, and `vpc/routes`

Packages