Migrate Azure Firewall Standard to Premium using Terraform

Article
10/27/2023

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.

If you use Terraform to deploy standard Azure Firewall with classic rules, you can modify your Terraform configuration file to migrate your firewall to Azure Firewall Premium using a Premium firewall policy.

In this article, you learn how to:

Deploy a standard Azure Firewall with classic rules using Terraform
Import the firewall rules into a premium firewall policy
Edit the Terraform configuration file to migrate the firewall

1. Configure your environment

Azure subscription: If you don't have an Azure subscription, create a free account before you begin.

Configure Terraform: If you haven't already done so, configure Terraform using one of the following options:

2. Implement the Terraform code

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

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

resource "random_pet" "prefix" {
  prefix = var.prefix
  length = 1
}
resource "azurerm_resource_group" "rg" {
  name     = "${random_pet.prefix.id}-rg"
  location = var.resource_group_location
}

resource "azurerm_virtual_network" "vnet" {
  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
}

resource "azurerm_subnet" "subnet" {
  name                 = "AzureFirewallSubnet"
  resource_group_name  = azurerm_resource_group.rg.name
  virtual_network_name = azurerm_virtual_network.vnet.name
  address_prefixes     = ["10.0.1.0/24"]
}

resource "azurerm_public_ip" "pip" {
  name                = "${random_pet.prefix.id}-pip"
  location            = azurerm_resource_group.rg.location
  resource_group_name = azurerm_resource_group.rg.name
  allocation_method   = "Static"
  sku                 = "Standard"
}

resource "azurerm_firewall" "main" {
  name                = "${random_pet.prefix.id}-fw"
  location            = azurerm_resource_group.rg.location
  resource_group_name = azurerm_resource_group.rg.name
  sku_name            = "AZFW_VNet"
  sku_tier            = "Standard"

  ip_configuration {
    name                 = "configuration"
    subnet_id            = azurerm_subnet.subnet.id
    public_ip_address_id = azurerm_public_ip.pip.id
  }
}

resource "azurerm_firewall_application_rule_collection" "app-rc" {
  name                = "${random_pet.prefix.id}-app-rc"
  azure_firewall_name = azurerm_firewall.main.name
  resource_group_name = azurerm_resource_group.rg.name
  priority            = 100
  action              = "Allow"

  rule {
    name = "testrule"

    source_addresses = [
      "10.0.0.0/16",
    ]

    target_fqdns = [
      "*.google.com",
    ]

    protocol {
      port = "443"
      type = "Https"
    }
  }
}

resource "azurerm_firewall_network_rule_collection" "net-rc" {
  name                = "${random_pet.prefix.id}-net-rc"
  azure_firewall_name = azurerm_firewall.main.name
  resource_group_name = azurerm_resource_group.rg.name
  priority            = 100
  action              = "Allow"

  rule {
    name = "dnsrule"

    source_addresses = [
      "10.0.0.0/16",
    ]

    destination_ports = [
      "53",
    ]

    destination_addresses = [
      "8.8.8.8",
      "8.8.4.4",
    ]

    protocols = [
      "TCP",
      "UDP",
    ]
  }
}

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 "prefix" {
  type        = string
  default     = "firewall-standard"
  description = "Prefix of the resource name"
}

3. 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.

4. 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.

5. 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.

6. Import the firewall rules into a premium policy

Now you have a standard firewall with classic rules. Next, create a premium Firewall Policy and import the rules from the firewall.

On the Azure portal, select Create a resource.
Search for firewall policy and select it.
Select Create.
For Resource group select test-resources .
For Name, type prem-pol.
For Region, select East US.
For Policy tier, select Premium.
Select Next: DNS Settings, and continue until you reach the Rules page.
On the Rules page, select Import rules from an Azure Firewall.
Select testfirewall, and then select Import.
Select Review + create.
Select Create.

7. Edit the Terraform configuration file to migrate the firewall

Open the main.tf file, and make the following changes:

Add the following 'data' section:

data "azurerm_firewall_policy" "prem-pol" {
  name                 = "prem-pol"
  resource_group_name  = azurerm_resource_group.rg.name
}

Modify the firewall resource:

 resource "azurerm_firewall" "fw" {
     name                = "testfirewall"
     location            = azurerm_resource_group.rg.location
     resource_group_name = azurerm_resource_group.rg.name
     firewall_policy_id  = data.azurerm_firewall_policy.prem-pol.id
     sku_tier            = "Premium"

 ip_configuration {
     name                 = "configuration"
     subnet_id            = azurerm_subnet.subnet.id
     public_ip_address_id = azurerm_public_ip.pip.id
 }
}

Delete the classic rule collections:

resource "azurerm_firewall_application_rule_collection" "app-rc" {
  name                = "apptestcollection"
  azure_firewall_name = azurerm_firewall.fw.name
  resource_group_name = azurerm_resource_group.rg.name
  priority            = 100
  action              = "Allow"

  rule {
    name = "testrule"

    source_addresses = [
      "10.0.0.0/16",
    ]

    target_fqdns = [
      "*.google.com",
    ]

    protocol {
      port = "443"
      type = "Https"
    }
  }
}

resource "azurerm_firewall_network_rule_collection" "net-rc" {
  name                = "nettestcollection"
  azure_firewall_name = azurerm_firewall.fw.name
  resource_group_name = azurerm_resource_group.rg.name
  priority            = 100
  action              = "Allow"

  rule {
    name = "dnsrule"

    source_addresses = [
      "10.0.0.0/16",
    ]

    destination_ports = [
      "53",
    ]

    destination_addresses = [
      "8.8.8.8",
      "8.8.4.4",
    ]

    protocols = [
      "TCP",
      "UDP",
    ]
  }
}

8. Apply the modified Terraform execution plan

terraform plan -out main.tfplan
terraform apply main.tfplan

9. Verify the results

Select the test-resources resource group.
Select the testfirewall resource.
Verify the Firewall sku is Premium.
Verify the firewall is using the prem-pol firewall policy.

10. Clean up resources

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

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.
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

Learn more about using Terraform in Azure

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Migrate Azure Firewall Standard to Premium using Terraform

1. Configure your environment

2. Implement the Terraform code

3. Initialize Terraform

4. Create a Terraform execution plan

5. Apply a Terraform execution plan

6. Import the firewall rules into a premium policy

7. Edit the Terraform configuration file to migrate the firewall

8. Apply the modified Terraform execution plan

9. Verify the results

10. Clean up resources

Troubleshoot Terraform on Azure

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