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Create on-premises virtual network in Azure using Terraform

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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.

This article shows how to implement an on-premises network in Azure. You can replace the sample network with a private virtual network. To do so, modify the subnet IP addresses to suit your environment.

In this article, you learn how to:

  • Implement an on-premises VNet in hub-spoke topology
  • Create hub network appliance resources
  • Create on-premises virtual machine
  • Create on-premises virtual private network gateway

1. Configure your environment

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

2. Implement the Terraform code

  1. Make the example directory created in the first article of this series the current directory.

  2. Create a file named on-prem.tf and insert the following code:

    locals {
    onprem-location       = "eastus"
    onprem-resource-group = "onprem-vnet-rg"
    prefix-onprem         = "onprem"
}

resource "azurerm_resource_group" "onprem-vnet-rg" {
    name     = local.onprem-resource-group
    location = local.onprem-location
}

resource "azurerm_virtual_network" "onprem-vnet" {
    name                = "onprem-vnet"
    location            = azurerm_resource_group.onprem-vnet-rg.location
    resource_group_name = azurerm_resource_group.onprem-vnet-rg.name
    address_space       = ["192.168.0.0/16"]

    tags = {
    environment = local.prefix-onprem
    }
}

resource "azurerm_subnet" "onprem-gateway-subnet" {
    name                 = "GatewaySubnet"
    resource_group_name  = azurerm_resource_group.onprem-vnet-rg.name
    virtual_network_name = azurerm_virtual_network.onprem-vnet.name
    address_prefixes     = ["192.168.255.224/27"]
}

resource "azurerm_subnet" "onprem-mgmt" {
    name                 = "mgmt"
    resource_group_name  = azurerm_resource_group.onprem-vnet-rg.name
    virtual_network_name = azurerm_virtual_network.onprem-vnet.name
    address_prefixes     = ["192.168.1.128/25"]
}

resource "azurerm_public_ip" "onprem-pip" {
    name                         = "${local.prefix-onprem}-pip"
    location            = azurerm_resource_group.onprem-vnet-rg.location
    resource_group_name = azurerm_resource_group.onprem-vnet-rg.name
    allocation_method   = "Dynamic"

    tags = {
        environment = local.prefix-onprem
    }
}

resource "azurerm_network_interface" "onprem-nic" {
    name                 = "${local.prefix-onprem}-nic"
    location             = azurerm_resource_group.onprem-vnet-rg.location
    resource_group_name  = azurerm_resource_group.onprem-vnet-rg.name
    enable_ip_forwarding = true

    ip_configuration {
    name                          = local.prefix-onprem
    subnet_id                     = azurerm_subnet.onprem-mgmt.id
    private_ip_address_allocation = "Dynamic"
    public_ip_address_id          = azurerm_public_ip.onprem-pip.id
    }
}

# Create Network Security Group and rule
resource "azurerm_network_security_group" "onprem-nsg" {
    name                = "${local.prefix-onprem}-nsg"
    location            = azurerm_resource_group.onprem-vnet-rg.location
    resource_group_name = azurerm_resource_group.onprem-vnet-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 = "*"
    }

    tags = {
        environment = "onprem"
    }
}

resource "azurerm_subnet_network_security_group_association" "mgmt-nsg-association" {
    subnet_id                 = azurerm_subnet.onprem-mgmt.id
    network_security_group_id = azurerm_network_security_group.onprem-nsg.id
}

resource "azurerm_virtual_machine" "onprem-vm" {
    name                  = "${local.prefix-onprem}-vm"
    location              = azurerm_resource_group.onprem-vnet-rg.location
    resource_group_name   = azurerm_resource_group.onprem-vnet-rg.name
    network_interface_ids = [azurerm_network_interface.onprem-nic.id]
    vm_size               = var.vmsize

    storage_image_reference {
    publisher = "Canonical"
    offer     = "UbuntuServer"
    sku       = "16.04-LTS"
    version   = "latest"
    }

    storage_os_disk {
    name              = "myosdisk1"
    caching           = "ReadWrite"
    create_option     = "FromImage"
    managed_disk_type = "Standard_LRS"
    }

    os_profile {
    computer_name  = "${local.prefix-onprem}-vm"
    admin_username = var.username
    admin_password = var.password
    }

    os_profile_linux_config {
    disable_password_authentication = false
    }

    tags = {
    environment = local.prefix-onprem
    }
}

resource "azurerm_public_ip" "onprem-vpn-gateway1-pip" {
    name                = "${local.prefix-onprem}-vpn-gateway1-pip"
    location            = azurerm_resource_group.onprem-vnet-rg.location
    resource_group_name = azurerm_resource_group.onprem-vnet-rg.name

    allocation_method = "Dynamic"
}

resource "azurerm_virtual_network_gateway" "onprem-vpn-gateway" {
    name                = "onprem-vpn-gateway1"
    location            = azurerm_resource_group.onprem-vnet-rg.location
    resource_group_name = azurerm_resource_group.onprem-vnet-rg.name

    type     = "Vpn"
    vpn_type = "RouteBased"

    active_active = false
    enable_bgp    = false
    sku           = "VpnGw1"

    ip_configuration {
    name                          = "vnetGatewayConfig"
    public_ip_address_id          = azurerm_public_ip.onprem-vpn-gateway1-pip.id
    private_ip_address_allocation = "Dynamic"
    subnet_id                     = azurerm_subnet.onprem-gateway-subnet.id
    }
    depends_on = [azurerm_public_ip.onprem-vpn-gateway1-pip]

}

Troubleshoot Terraform on Azure

Troubleshoot common problems when using Terraform on Azure

Next steps

Create a hub virtual network with Terraform in Azure