Quickstart: Create an Azure NAT Gateway using Terraform

Get started with Azure NAT Gateway using Terraform. This Terraform file deploys a virtual network, a NAT gateway resource, and Ubuntu virtual machine. The Ubuntu virtual machine is deployed to a subnet that is associated with the NAT gateway resource.

The script also generates a random SSH public key and associates it with the virtual machine for secure access. The public key is outputted at the end of the script execution.

The script uses the Random and AzAPI providers in addition to the AzureRM provider. The Random provider is used to generate a unique name for the resource group and the SSH key. The AzAPI provider is used to generate the SSH public key.

As with the public key, the names of the created resource group, virtual network, subnet, and NAT gateway are printed when the script is run.

Terraform enables the definition, preview, and deployment of cloud infrastructure. Using Terraform, you create configuration files using HCL syntax. The HCL syntax allows you to specify the cloud provider - such as Azure - and the elements that make up your cloud infrastructure. After you create your configuration files, you create an execution plan that allows you to preview your infrastructure changes before they're deployed. Once you verify the changes, you apply the execution plan to deploy the infrastructure.

Prerequisites

• An Azure account with an active subscription. You can create an account for free.

• Install and configure Terraform.

Implement the Terraform code

1. Create a directory in which to test and run the sample Terraform code and make it the current directory.

2. Create a file named main.tf and insert the following code:

   # Resource Group
   resource "azurerm_resource_group" "rg" {
     location = var.resource_group_location
     name     = "${random_pet.prefix.id}-rg"
   }
   
   # Virtual Network
   resource "azurerm_virtual_network" "my_terraform_network" {
     name                = "${random_pet.prefix.id}-vnet"
     address_space       = ["10.0.0.0/16"]
     location            = azurerm_resource_group.rg.location
     resource_group_name = azurerm_resource_group.rg.name
   }
   
   # Subnet 1
   resource "azurerm_subnet" "my_terraform_subnet_1" {
     name                 = "subnet-1"
     resource_group_name  = azurerm_resource_group.rg.name
     virtual_network_name = azurerm_virtual_network.my_terraform_network.name
     address_prefixes     = ["10.0.0.0/24"]
   }
   
   # Public IP address for NAT gateway
   resource "azurerm_public_ip" "my_public_ip" {
     name                = "public-ip-nat"
     location            = azurerm_resource_group.rg.location
     resource_group_name = azurerm_resource_group.rg.name
     allocation_method   = "Static"
     sku                 = "Standard"
   }
   
   # NAT Gateway
   resource "azurerm_nat_gateway" "my_nat_gateway" {
     name                = "nat-gateway"
     location            = azurerm_resource_group.rg.location
     resource_group_name = azurerm_resource_group.rg.name
   }
   
   # Associate NAT Gateway with Public IP
   resource "azurerm_nat_gateway_public_ip_association" "example" {
     nat_gateway_id       = azurerm_nat_gateway.my_nat_gateway.id
     public_ip_address_id = azurerm_public_ip.my_public_ip.id
   }
   
   # Associate NAT Gateway with Subnet
   resource "azurerm_subnet_nat_gateway_association" "example" {
     subnet_id      = azurerm_subnet.my_terraform_subnet_1.id
     nat_gateway_id = azurerm_nat_gateway.my_nat_gateway.id
   }
   
   # Create public IP for virtual machine
   resource "azurerm_public_ip" "my_public_ip_vm" {
     name                = "public-ip-vm"
     location            = azurerm_resource_group.rg.location
     resource_group_name = azurerm_resource_group.rg.name
     allocation_method   = "Static"
     sku                 = "Standard"
   }
   
   # Create Network Security Group and rule
   resource "azurerm_network_security_group" "my_terraform_nsg" {
     name                = "nsg-1"
     location            = azurerm_resource_group.rg.location
     resource_group_name = azurerm_resource_group.rg.name
   
     security_rule {
       name                       = "SSH"
       priority                   = 1001
       direction                  = "Inbound"
       access                     = "Allow"
       protocol                   = "Tcp"
       source_port_range          = "*"
       destination_port_range     = "22"
       source_address_prefix      = "*"
       destination_address_prefix = "*"
     }
   }
   
   # Create network interface
   resource "azurerm_network_interface" "my_terraform_nic" {
     name                = "nic-1"
     location            = azurerm_resource_group.rg.location
     resource_group_name = azurerm_resource_group.rg.name
   
     ip_configuration {
       name                          = "my_nic_configuration"
       subnet_id                     = azurerm_subnet.my_terraform_subnet_1.id
       private_ip_address_allocation = "Dynamic"
       public_ip_address_id          = azurerm_public_ip.my_public_ip_vm.id
     }
   }
   
   # Connect the security group to the network interface
   resource "azurerm_network_interface_security_group_association" "example" {
     network_interface_id      = azurerm_network_interface.my_terraform_nic.id
     network_security_group_id = azurerm_network_security_group.my_terraform_nsg.id
   }
   
   # Generate random text for a unique storage account name
   resource "random_id" "random_id" {
     keepers = {
       # Generate a new ID only when a new resource group is defined
       resource_group = azurerm_resource_group.rg.name
     }
   
     byte_length = 8
   }
   
   # Create storage account for boot diagnostics
   resource "azurerm_storage_account" "my_storage_account" {
     name                     = "diag${random_id.random_id.hex}"
     location                 = azurerm_resource_group.rg.location
     resource_group_name      = azurerm_resource_group.rg.name
     account_tier             = "Standard"
     account_replication_type = "LRS"
   }
   
   # Create virtual machine
   resource "azurerm_linux_virtual_machine" "my_terraform_vm" {
     name                  = "vm-1"
     location              = azurerm_resource_group.rg.location
     resource_group_name   = azurerm_resource_group.rg.name
     network_interface_ids = [azurerm_network_interface.my_terraform_nic.id]
     size                  = "Standard_DS1_v2"
   
     os_disk {
       name                 = "myOsDisk"
       caching              = "ReadWrite"
       storage_account_type = "Premium_LRS"
     }
   
     source_image_reference {
       publisher = "Canonical"
       offer     = "0001-com-ubuntu-server-jammy"
       sku       = "22_04-lts-gen2"
       version   = "latest"
     }
   
     computer_name  = "hostname"
     admin_username = var.username
   
     admin_ssh_key {
       username   = var.username
       public_key = jsondecode(azapi_resource_action.ssh_public_key_gen.output).publicKey
     }
   
     boot_diagnostics {
       storage_account_uri = azurerm_storage_account.my_storage_account.primary_blob_endpoint
     }
   }
   
   resource "random_pet" "prefix" {
     prefix = var.resource_group_name_prefix
     length = 1
   }
   

3. Create a file named outputs.tf and insert the following code:

   output "resource_group_name" {
     description = "The name of the created resource group."
     value       = azurerm_resource_group.rg.name
   }
   
   output "virtual_network_name" {
     description = "The name of the created virtual network."
     value       = azurerm_virtual_network.my_terraform_network.name
   }
   
   output "subnet_name_1" {
     description = "The name of the created subnet 1."
     value       = azurerm_subnet.my_terraform_subnet_1.name
   }
   
   output "nat_gateway"{
     description = "The name of the created NAT gateway."
     value       = azurerm_nat_gateway.my_nat_gateway.id
   }
   

4. Create a file named providers.tf and insert the following code:

   terraform {
     required_providers {
       azapi = {
         source  = "azure/azapi"
         version = "~>1.5"
       }
       azurerm = {
         source  = "hashicorp/azurerm"
         version = "~>3.0"
       }
       random = {
         source  = "hashicorp/random"
         version = "~>3.0"
       }
     }
   }
   
   provider "azurerm" {
     features {}
   }
   

5. Create a file named ssh.tf and insert the following code:

   resource "random_pet" "ssh_key_name" {
     prefix    = "ssh"
     separator = ""
   }
   
   resource "azapi_resource_action" "ssh_public_key_gen" {
     type        = "Microsoft.Compute/sshPublicKeys@2022-11-01"
     resource_id = azapi_resource.ssh_public_key.id
     action      = "generateKeyPair"
     method      = "POST"
   
     response_export_values = ["publicKey", "privateKey"]
   }
   
   resource "azapi_resource" "ssh_public_key" {
     type      = "Microsoft.Compute/sshPublicKeys@2022-11-01"
     name      = random_pet.ssh_key_name.id
     location  = azurerm_resource_group.rg.location
     parent_id = azurerm_resource_group.rg.id
   }
   
   output "key_data" {
     value = jsondecode(azapi_resource_action.ssh_public_key_gen.output).publicKey
   }
   

6. Create a file named variables.tf and insert the following code:

   variable "resource_group_location" {
     type        = string
     default     = "eastus"
     description = "Location of the resource group."
   }
   
   variable "resource_group_name_prefix" {
     type        = string
     default     = "rg"
     description = "Prefix of the resource group name that's combined with a random ID so name is unique in your Azure subscription."
   }
   
   variable "username" {
     type        = string
     description = "The username for the local account that will be created on the new VM."
     default     = "azureuser"
   }
   

Initialize Terraform

Run terraform init to initialize the Terraform deployment. This command downloads the Azure provider required to manage your Azure resources.

terraform init -upgrade

Key points:

• The -upgrade parameter upgrades the necessary provider plugins to the newest version that complies with the configuration's version constraints.

Create a Terraform execution plan

Run terraform plan to create an execution plan.

terraform plan -out main.tfplan

Key points:

• The terraform plan command creates an execution plan, but doesn't execute it. Instead, it determines what actions are necessary to create the configuration specified in your configuration files. This pattern allows you to verify whether the execution plan matches your expectations before making any changes to actual resources.
• The optional -out parameter allows you to specify an output file for the plan. Using the -out parameter ensures that the plan you reviewed is exactly what is applied.

Apply a Terraform execution plan

Run terraform apply to apply the execution plan to your cloud infrastructure.

terraform apply main.tfplan

Key points:

• The example terraform apply command assumes you previously ran terraform plan -out main.tfplan.
• If you specified a different filename for the -out parameter, use that same filename in the call to terraform apply.
• If you didn't use the -out parameter, call terraform apply without any parameters.

Verify the results

resource_group_name=$(terraform output -raw resource_group_name)

    nat_gateway=$(terraform output -raw nat_gateway)

az network nat gateway show \
    --resource-group $resource_group_name \
    --ids $nat_gateway

$resource_group_name=$(terraform output -raw resource_group_name)

$nat_gateway=$(terraform output -raw nat_gateway)

$nat = @{
    Name = $nat_gateway
    ResourceGroupName = $resource_group_name
}
Get-AzNatGateway @nat

Clean up resources

When you no longer need the resources created via Terraform, do the following steps:

1. Run terraform plan and specify the destroy flag.

   terraform plan -destroy -out main.destroy.tfplan
   

   Key points:

   • The terraform plan command creates an execution plan, but doesn't execute it. Instead, it determines what actions are necessary to create the configuration specified in your configuration files. This pattern allows you to verify whether the execution plan matches your expectations before making any changes to actual resources.
   • The optional -out parameter allows you to specify an output file for the plan. Using the -out parameter ensures that the plan you reviewed is exactly what is applied.

2. Run terraform apply to apply the execution plan.

   terraform apply main.destroy.tfplan
   

Troubleshoot Terraform on Azure

Troubleshoot common problems when using Terraform on Azure.

Next steps