»Transit Gateway Attachments
AWS provides a network transit hub called a Transit Gateway. One or more VPCs and HVNs can connect to a Transit Gateway through a Transit Gateway (TGW) Attachment.
The Transit Gateway must be created in an AWS account and shared with the HVN through the AWS Resource Access Manager. The TGW and Resource share must also be in the same region as the HVN. When a TGW Attachment is created in HCP, the shared resource is identified by the provided Resource share Amazon Resource Name (ARN) and the Transit gateway ID. Then, an outgoing attachment request is initiated. The attachment request must be approved in the AWS account before HCP will route traffic through the TGW.
»Sharing a Transit Gateway Resource
To share a TGW with an HVN, you will need the AWS account ID of the desired HVN. You can find this by navigating to the Transit gateway attachments > Create attachment section of your HVN in the HCP Portal.
»Creating an Attachment
HCP requires the Transit gateway ID and Resource shared ARN to locate the TGW, and then issues an attachment request.
Creating a TGW Attachment can be done through the HCP Portal or with the HCP Terraform provider.
All HVN routing is managed by HVN Routes. See Connect an Amazon Transit Gateway to your HashiCorp Virtual Network for steps on how to add or modify traffic sent through a TGW Attachment.