How to Import an Azure Subnet NAT Gateway Association into Terraform

Import Azure Subnet NAT Gateway Association with Terraback (recommended)

Terraback reverse-engineers your live infrastructure: it reads the Azure Networking resource with read-only credentials, generates the HCL, and produces the exact import block. Two commands take you from a live Azure Subnet NAT Gateway Association to managed Terraform.

terraback scan all azure --subscription-id YOUR_ID

terraback azure 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 = azurerm_subnet_nat_gateway_association.main
  id = "/subscriptions/00000000-0000-0000-0000-000000000000/resourceGroups/prod-rg/providers/Microsoft.Network/virtualNetworks/prod-vnet/subnets/app-subnet"
}

Example azurerm_subnet_nat_gateway_association configuration

Here is a realistic Azure Subnet NAT Gateway Association block. Terraback generates a fuller version from your actual resource attributes; this is a minimal, valid starting point.

resource "azurerm_subnet_nat_gateway_association" "main" {
  subnet_id      = azurerm_subnet.app.id
  nat_gateway_id = azurerm_nat_gateway.main.id
}

Gotchas when importing a Azure Subnet NAT Gateway Association

• The import ID is the SUBNET's ARM resource ID, not the NAT gateway's; the association is modeled as a property of the subnet.
• A subnet can be associated with only one NAT gateway, so there is exactly one association resource per subnet.
• Avoid also setting the association inline on the azurerm_subnet resource; managing it both inline and via this resource causes Terraform to fight itself on every plan.
• The NAT gateway and the subnet's virtual network must be in the same region and subscription.

Doing it manually with terraform import

The native approach is to write the azurerm_subnet_nat_gateway_association block by hand, then run terraform import azurerm_subnet_nat_gateway_association.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 Azure resources