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Create a hub virtual network in Azure by 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.

The hub virtual network acts as the central point of connectivity to the on-premises network. The virtual network hosts shared services consumed by workloads hosted in the spoke virtual networks. For demo purposes, no shared services are implemented in this article.

In this article, you learn how to:

  • Implement the hub virtual network in a hub-and-spoke topology.
  • Create a hub jumpbox virtual machine.
  • Create a hub virtual private network gateway.
  • Create hub and on-premises gateway connections.

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

The hub network consists of the following components:

  • A hub virtual network
  • A hub virtual network gateway
  • Hub gateway connections

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

  2. In the example directory, create a file named hub-vnet.tf.

  3. Insert the following code:

    locals {
    prefix-hub         = "hub"
    hub-location       = "eastus"
    hub-resource-group = "hub-vnet-rg"
    shared-key         = "4-v3ry-53cr37-1p53c-5h4r3d-k3y"
}

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

resource "azurerm_virtual_network" "hub-vnet" {
    name                = "${local.prefix-hub}-vnet"
    location            = azurerm_resource_group.hub-vnet-rg.location
    resource_group_name = azurerm_resource_group.hub-vnet-rg.name
    address_space       = ["10.0.0.0/16"]

    tags = {
    environment = "hub-spoke"
    }
}

resource "azurerm_subnet" "hub-gateway-subnet" {
    name                 = "GatewaySubnet"
    resource_group_name  = azurerm_resource_group.hub-vnet-rg.name
    virtual_network_name = azurerm_virtual_network.hub-vnet.name
    address_prefixes     = ["10.0.255.224/27"]
}

resource "azurerm_subnet" "hub-mgmt" {
    name                 = "mgmt"
    resource_group_name  = azurerm_resource_group.hub-vnet-rg.name
    virtual_network_name = azurerm_virtual_network.hub-vnet.name
    address_prefixes       = ["10.0.0.64/27"]
}

resource "azurerm_subnet" "hub-dmz" {
    name                 = "dmz"
    resource_group_name  = azurerm_resource_group.hub-vnet-rg.name
    virtual_network_name = azurerm_virtual_network.hub-vnet.name
    address_prefixes       = ["10.0.0.32/27"]
}

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

    ip_configuration {
    name                          = local.prefix-hub
    subnet_id                     = azurerm_subnet.hub-mgmt.id
    private_ip_address_allocation = "Dynamic"
    }

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

#Virtual Machine
resource "azurerm_virtual_machine" "hub-vm" {
    name                  = "${local.prefix-hub}-vm"
    location              = azurerm_resource_group.hub-vnet-rg.location
    resource_group_name   = azurerm_resource_group.hub-vnet-rg.name
    network_interface_ids = [azurerm_network_interface.hub-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-hub}-vm"
    admin_username = var.username
    admin_password = var.password
    }

    os_profile_linux_config {
    disable_password_authentication = false
    }

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

# Virtual Network Gateway
resource "azurerm_public_ip" "hub-vpn-gateway1-pip" {
    name                = "hub-vpn-gateway1-pip"
    location            = azurerm_resource_group.hub-vnet-rg.location
    resource_group_name = azurerm_resource_group.hub-vnet-rg.name

    allocation_method = "Dynamic"
}

resource "azurerm_virtual_network_gateway" "hub-vnet-gateway" {
    name                = "hub-vpn-gateway1"
    location            = azurerm_resource_group.hub-vnet-rg.location
    resource_group_name = azurerm_resource_group.hub-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.hub-vpn-gateway1-pip.id
    private_ip_address_allocation = "Dynamic"
    subnet_id                     = azurerm_subnet.hub-gateway-subnet.id
    }
    depends_on = [azurerm_public_ip.hub-vpn-gateway1-pip]
}

resource "azurerm_virtual_network_gateway_connection" "hub-onprem-conn" {
    name                = "hub-onprem-conn"
    location            = azurerm_resource_group.hub-vnet-rg.location
    resource_group_name = azurerm_resource_group.hub-vnet-rg.name

    type           = "Vnet2Vnet"
    routing_weight = 1

    virtual_network_gateway_id      = azurerm_virtual_network_gateway.hub-vnet-gateway.id
    peer_virtual_network_gateway_id = azurerm_virtual_network_gateway.onprem-vpn-gateway.id

    shared_key = local.shared-key
}

resource "azurerm_virtual_network_gateway_connection" "onprem-hub-conn" {
    name                = "onprem-hub-conn"
    location            = azurerm_resource_group.onprem-vnet-rg.location
    resource_group_name = azurerm_resource_group.onprem-vnet-rg.name
    type                            = "Vnet2Vnet"
    routing_weight = 1
    virtual_network_gateway_id      = azurerm_virtual_network_gateway.onprem-vpn-gateway.id
    peer_virtual_network_gateway_id = azurerm_virtual_network_gateway.hub-vnet-gateway.id

    shared_key = local.shared-key
}

Troubleshoot Terraform on Azure

Troubleshoot common problems when using Terraform on Azure

Next steps

Create a hub virtual network appliance with Terraform in Azure