How to Import an AWS Transit Gateway Route into Terraform

Import AWS Transit Gateway Route with Terraback (recommended)

Terraback reverse-engineers your live infrastructure: it reads the Amazon VPC Transit Gateway resource with read-only credentials, generates the HCL, and produces the exact import block. Two commands take you from a live AWS Transit Gateway Route to managed Terraform.

terraback scan all aws --region us-east-1

terraback aws import --method bulk

The Terraform import block

Terraback emits a Terraform 1.5+ import block like the one below. Because the block lives in your configuration, the import is reviewable in a pull request and repeatable across environments.

import {
  to = aws_ec2_transit_gateway_route.example
  id = "tgw-rtb-12345678_0.0.0.0/0"
}

Example aws_ec2_transit_gateway_route configuration

Here is a realistic AWS Transit Gateway Route block. Terraback generates a fuller version from your actual resource attributes; this is a minimal, valid starting point.

resource "aws_ec2_transit_gateway_route" "example" {
  destination_cidr_block         = "0.0.0.0/0"
  transit_gateway_attachment_id  = "tgw-attach-12345678"
  transit_gateway_route_table_id = "tgw-rtb-12345678"
}

Gotchas when importing a AWS Transit Gateway Route

• A route is a child of an aws_ec2_transit_gateway_route_table; the import ID joins the route table ID and the destination CIDR with an underscore, and the parent route table must already be in state.
• Use the underscore separator exactly as shown (tgw-rtb-...\_0.0.0.0/0); the CIDR itself keeps its slash, so do not confuse the route-table-to-CIDR underscore with the CIDR's own slash.
• Blackhole routes have no transit_gateway_attachment_id; for those set blackhole = true instead, or the apply after import will fail validation.
• Propagated routes are managed by aws_ec2_transit_gateway_route_table_propagation, not this resource; only import static routes here, and avoid importing a CIDR that is actually propagated.

Doing it manually with terraform import

The native approach is to write the aws_ec2_transit_gateway_route block by hand, then run terraform import aws_ec2_transit_gateway_route.example <import-id> for every resource, one at a time. That works for a handful of resources, but it does not scale: you author all the HCL yourself and repeat the command for each item. Terraback generates the HCL and the import blocks for your whole account in one pass.

Import other AWS resources