Terraform-Azure-Virtual-WAN-no-Azure-Firewall

The Repo

This blog focuses on this repo: https://github.com/marckean/Terraform-Azure-Virtual-WAN-no-Azure-Firewall

Overview

Multi-environment (Prod / Non-Prod / Shared Services) using Azure Virtual WAN, with 3 vWAN hubs in the same region to provide total isolation of the network. This focuses on the Azure side of things, as a second step to this, you would connect to this from on-prem using either ExpressRoute or VPN.

Pretty much the requirement here is that Prod can talk to Shared ServicesNon-Prod can talk to Shared Services, but Prod & Non-Prod can’t talk to each other. There is total isolation between Prod & Non-Prod.

Deployment Instructions

[!NOTE] In the real world for large enterprise companies, you would most likely already have access to Terraform Cloud and also have a CI/CD setup. So I assume you already know how Terraform works with respect to deployment. In this instance, you take these Terraform files from this repo and build on top of these, do what you will.

Else, as a quick start, you can run this as a test, in a non-prod/dev environment to have a play and see how/what deploys into Azure.

Below the instructions to quickly run the Terraform in this repository with the least amount of effort. We will be using GitHub in this example, however you can use any other type of Git that you or your team are familiar with.

[!NOTE] Cloud Shell automatically has the latest version of Terraform installed. Also, Terraform automatically uses information from the current Azure subscription. As a result, there’s no installation or configuration required.

  1. Connect to CloudDrive (Azure Files Share)
  2. Copy files from this reop to Azure CloudDrive
  3. Setup the Terraform State in Azure Blob Storage
  4. Apply the Azure Storage Account key securely to an environment variable

Detailed instructions:

Use VS Code

Download and Install Visual Studio Code – that is, if you don’t have it already installed already.

Extentions you will need with VS code

Extension NameDescription
Azure ToolsMicrosoft Azure support for Visual Studio Code is provided through a rich set of extensions that make it easy to discover and interact with the cloud services that power your applications.

This includes Azure CLI

Installing the Azure Tools extension installs all of the extensions you need. Some of these extensions will also install the Azure Account extension which provides a single Azure login and subscription filtering experience
HashiCorp TerraformThe HashiCorp Terraform Visual Studio Code (VS Code) extension adds syntax highlighting and other editing features for Terraform files using the Terraform Language Server.

Sign In to Azure

To sign in to your Azure Account, in VS Code, hit F1 or CTRL+SHIFT+P, then type in Sign in to Azure.

[!NOTE] This will be the account used in which Terraform will deploy resources into Azure with.

You may be prompted for access to your computer’s secure credential storage service (e.g. Keychain Access on MacOS or Windows Credential Manager) so you don’t need to sign in every time you start VS Code.

Open Azure Cloud Shell

In VS Code, hit F1 or CTRL+SHIFT+P again, then open Bash in Cloud Shell.

List CloudDrive

Copy files from the GitHub repo, to Azure CloudDrive, so you can access them using Azure CLI. Azure CloudDrive is simply an Azure Files Share.

Assuming you have previously connected to Azure Cloud Shell before and already setup the Storage Account more details here. Next, you will need to connect to the Azure Files share in which CloudDrive is configured to use, so you can copy and paste the Terraform files in this repo. To see which Azure Files share CloudDrive is using, run the df command.

justin@Azure:~$ df
Filesystem                                          1K-blocks   Used  Available Use% Mounted on
overlay                                             29711408 5577940   24117084  19% /
tmpfs                                                 986716       0     986716   0% /dev
tmpfs                                                 986716       0     986716   0% /sys/fs/cgroup
/dev/sda1                                           29711408 5577940   24117084  19% /etc/hosts
shm                                                    65536       0      65536   0% /dev/shm
//mystoragename.file.core.windows.net/fileshareName 5368709120    64 5368709056   1% /home/justin/clouddrive
justin@Azure:~$

There it is: //mystoragename.file.core.windows.net/fileshareName

In this instance, the storage account is mystoragename and the Azure Files Share is fileshareName.

Copy the repo files to the CloudDrive

Next, you can either use Azure Storage Explorer to copy the files to CloudDrive.

Or you can Mount SMB Azure file share you need to do is mount the Azure Files Share on your local device, Windows, Linux, macOS – https://docs.microsoft.com/en-us/azure/storage/files/storage-how-to-use-files-windows.

Simply create a folder in the root of Azure CloudDrive and copy the files this repo to it.

If it’s easier, you can also fork this repo so that the files local to your machine.

Open Azure CloudDrive in VS Code

Either open the folder directly from the SMB mapped network drive, or you can use the VS Code Azure Storage extension and connect directly to the Azure Files share from within VS Code.

Terraform State

The state for Terraform should live in a stateful place which is central, common, secure and accessible to everything. E.g. Azure Storage is a perfect candidate. You’ll need to setup an Azure Storage account with a container. Recommendation would be to apply Azure resource locking on this storage account so that it doesn’t get deleted accidentally. Also, maybe apply some tags to this storage account, clearly specifying what it’s used for. Edit the terraform.tf and change the values for backend "azurerm" to suit your own Azure Storage Account. key = "prod.terraform.tfstate" the same.

You can keep key = "prod.terraform.tfstate" as is, no change.

terraform {
  required_providers {
    azurerm = {
      source  = "hashicorp/azurerm"
      version = ">= 2.68.0" # was 2.46.1
    }
  }
  backend "azurerm" {
    resource_group_name  = "TerraformState_CloudShell"
    storage_account_name = "tfstatecloudshell2021"
    container_name       = "tfstate"
    key                  = "prod.terraform.tfstate"
  }
}

Azure Storage Key

While the terraform.tf file has all the other information for the Azure Storage account, one piece is missing, this is the Azure Storage account key. This is sensitive! So we use the Azure CLI environment variables to help us.

Azure CLI configuration

The Azure CLI allows for user configuration for settings such as logging, data collection, and default argument values. The CLI offers a convenience command for managing some defaults, az config. Other values can be set in a configuration file or with environment variables.

Terraform needs the Azure Storage account key in order to read/write the Terraform state file. In order to not store the Azure storage account key to disk, we will make use of the Azure CLI environment variable access_key.

Environment Variable

NameTypeDescription
access_keyStringThe default access key to use for az batch commands. Only used with aad authorization

Run the following 2 lines. This will grab the Azure Storage account key and apply it’s value to the access_key environment variable in the Azure CLI:

ACCOUNT_KEY=$(az storage account keys list --resource-group $RESOURCE_GROUP_NAME --account-name $STORAGE_ACCOUNT_NAME --query '[0].value' -o tsv)
export ARM_ACCESS_KEY=$ACCOUNT_KEY

Using the access_key environment variable in the Azure CLI prevents you from storing the Azure Storage account key on disk, as per:

Variables to change for your deployment

In the variables.tf file, there’s a list of variables to change to suit your own environment. Make sure you run through this thoroughly and make the necessary changes. It should be fairly obvious which variables you need to change. For starters, one that you definitely would want to change is the Azure Subscription ID:

variable "connectivity_subscription_id" {
  type    = string
  default = "6bx002x5-54x6-4xb1-9xca-5bxefx18x0bx"
}

[!NOTE] For testing purposes, after changing the subscription ID, if you leave every other variable in tack, this will deploy with the current values

Provider Alias (optional)

We are using provider alias’s throughout, this gives us the flexibility to deploy across multiple subscriptions on a resource by resource basis. This means that on a per resource basis you’ll see this line included provider = azurerm.connectivity for every resource, here we’re specifying which Azure subscription to use.

If you want to deploy any resources to other subscriptions, e.g. the spoke Virtual Networks, you can.

Simply create another provider in the terraform.tf file, similar to:

Also create another variable in the variables.tf file similar to:

Now you’re done and ready to deploy.

Terraform deployment commands in Azure CLI

In the Azure CLI, run cd CloudDrive – at this point, you’re at the same location as what you see in the Azure Files Share that has been mounted.

  • Run ls to view the contents of the folder.
  • Run cd FolderName to change to the folder name containing the Terraform Files to which you created just before
  • Run Terraform Init to first initialise the folder to be used with Terraform

When running Terraform Init, the Azure Storage key is consumed by Terraform. You can see the key file here.

The contents of the look like:

> {
  "version": 4,
  "terraform_version": "1.0.2",
  "serial": 0,
  "lineage": "c2c4d0cb-b98f-4683-82cd-6f919faf26d8",
  "outputs": {},
  "resources": []
}
  • Option: Run Terraform Validate to validate the code. (if you just copied files directly fro this repo, then no errors should appear)
  • Run Terraform plan to see what will be deployed
  • Run Terraform apply -auto-approve to apply the configuration directly to Azure.

Deployed Items

The below is “the what”, what is deployed with this repository.

Azure Virtual WAN (vWAN)

Azure vWAN itself, only one deployed into a subscription named Connectivity.

vWAN hubs

A total of 3 virtual hubs are deployed in the same region inside of the one Azure vWAN. Each hub is earmarked to be used for each environment, Prod / Shared Services / Non-Prod.

Virtual Network Connections

This is fairly stock standard, spoke vNets in each environment Prod / Shared Services / Non-Prod connected to the relevant vWAN hub.

Virtual Hub Routing

As for the custom route tables in the vWAN hubs, this is what the effective routes look like:

Route Table NamePrefixNext Hop TypeNext Hop
con-aue-vwanrt-prod10.1.0.0/21Virtual Network Connectioncon-aue-vnt-prod_spoke_01
con-aue-vwanrt-prod10.1.16.0/21Remote Hubcon-aue-vwanhub-ss-003
con-aue-vwanrt-ss10.1.16.0/21Virtual Network Connectioncon-aue-vwanconn-ss_spoke_01
con-aue-vwanrt-ss10.1.0.0/21Remote Hubcon-aue-vwanhub-prod-001
con-aue-vwanrt-ss10.1.8.0/21Remote Hubcon-aue-vwanhub-non_prod-002
con-aue-vwanrt-non_prod10.1.8.0/21Virtual Network Connectioncon-aue-vwanconn-nonprod_spoke_01
con-aue-vwanrt-non_prod10.1.16.0/21Remote Hubcon-aue-vwanhub-ss-003

Virtual Networks

The following Virtual Networks are deployed to BHP’s Petroleum OT Production environment:

NameAddress SpaceSubnetSubnet Address Range
con-aue-vnt-nonprod_spoke_0110.1.8.0/21con-aue-001
con-aue-002
10.1.8.0/24
10.1.9.0/24
con-aue-vnt-prod_spoke_0110.1.0.0/21con-aue-001
con-aue-002
10.1.0.0/24
10.1.1.0/24
con-aue-vnt-ss_spoke_0110.1.16.0/21con-aue-001
con-aue-002
10.1.16.0/24
10.1.17.0/24

Understanding vWAN routing

Routing in vWAN can get a little complicated… But I’ve taken snippets from this video (as shown below) to help explain vWAN routing in more detail.

This covers:

  • Connection & Propagation
  • Route Tables
  • Custom Route Tables
  • Putting it all together

Connection & Propagation

Connections

  • Anything that is connected to a VirtualHub​
    • Vnets – HubVnetConnection​
    • VPN GW – VPNConnection​
    • ER GW – ERConnection​
    • P2S GW – P2S config Connection​
  • Can have static routes, directing traffic for a tiered spoke through an NVA​

Propagation

Connections dynamically propagate routes to a route table. Routes can be propagated to one or multiple route tables. Propagating to the none route table implies that no routes are required to be propagates from that connection.

You can propagate routes to a route table directly, or you can propagate routes to route table labels. Labels provide a mechanism to logically group route tables and exist across all hubs. For example, the Default Route Table has a built-in label called Default. When users propagate connection routes to the Default label, it automatically applies to all the Default labelled Route Tables across every hub in the Virtual WAN. When creating a route table, you can add one or many labels to this route table.

  • Connections dynamically propagate routes to a route table
  • Routes can be propagated to one or multiple route tables
  • Route Tables across Hubs can be groups under labels, you can propagate routes to one or multiple route table labels

Association​

Association allows the connection to reach all the routes in the route table. Multiple connections can be associated to the same route table. VPN Sites, User VPN and ExpressRoute connections are required to be associated to the default route table. Each virtual hub has its own default route table, to which you can add static routes. A static route takes precedence over dynamically learned routes.

  • Each connection is associated to one route table
  • Custom RT used for vNets
  • Branches must be associated with the Default RT
Alt text

Route Tables

  • Collection of routes in each Hub
  • Each Hub may contain multiple Route Tables​
  • Each Hub always contains Default and None​
  • Route Tables across Hubs can be grouped under Labels​
  • Routes: Destination prefix -> Next Hop, example 10.0.1.0/24 ->  VNET_A_1_conn​

Routes​

  • Destination: CIDR prefix e.g. 10.0.1.0/24​
  • Next Hop: Connection, AzFW, Remote Hub​

Labels​

  • Collections of Route Tables across Hubs​
Alt text

Custom Route Tables

Alt text

Putting it all together

Alt text

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