IaaS DNS Forwarders

src/bicep/examples/iaas-dns-forwarders/README.md

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+# Azure IaaS DNS Forwarders example
+
+This example deploys DNS Forwarder Virtual Machines in the MLZ HUB, to enables proper resolution of Private Endpoint and internal domains accross all Virtual Networks.
+
+## What this example does
+
+### Follows best-practices
+
+This Infrastructure as Code deploys the components to follow best practices: [Private Link and DNS integration in hub and spoke network architectures](https://docs.microsoft.com/en-us/azure/cloud-adoption-framework/ready/azure-best-practices/private-link-and-dns-integration-at-scale#private-link-and-dns-integration-in-hub-and-spoke-network-architectures)
+
+### Configures proper DNS resolution in DoD Azure environments
+
+The two Windows DNS Servers are configured to act as DNS servers for all Virtual Networks, and then forward DNS requests three different ways, as depicted below.
+
+![DNS Forwarders diagram](diagram.png)
+
+1. Azure Private Endpoint-related DNS requests get forwarded to the Azure DNS server (168.63.129.16), which uses the Private DNS zones configured as part of MLZ.
+2. Active Directory-related DNS requests get forwarded to the Domain Controllers in the Identity tier.
+3. All other DNS requests (Internet...) get forwarded to the default server forwarder, typically DISA DNS servers.
+
+## Pre-requisites
+
+1. A Mission LZ deployment (a deployment of mlz.bicep)
+2. The outputs from a deployment of mlz.bicep (./src/bicep/examples/deploymentVariables.json).  
+
+See below for information on how to create the appropriate deployment variables file for use with this template.
+
+### Template Parameters
+
+Template Parameters Name       | Description
+---                            | ---
+vmNamePrefix                   | 3 to 12 characters VM name prefix. -01 and -02 will get appended to that prefix.
+vmAdminPassword                | local administrator password.
+nicPrivateIPAddresses          | array of two static IP addresses available in the HUB VNET subnet.
+extensionsFilesContainerUri    | uri to the storage account used to host the DSC configuration and custom script file (if not relying on the public repo)           
+extensionsFilesContainerSas    | storage account account SAS token used to host the DSC configuration and custom script file (if not relying on the public repo)  
+dnsServerForwardersIpAddresses | default DNS server forwarders (for instance: DISA's). Defaults to Azure DNS.
+conditionalDnsServerForwarders | array of conditional forwarders to create, including Azure Private DNS zones and Active Directory-related zones. Defaults to Azure US Government's private endpoint DNS zones.
+
+### Generate MLZ Variable File (deploymentVariables.json)
+
+For instructions on generating 'deploymentVariables.json' using both Azure PowerShell and Azure CLI, please see the [README at the root of the examples folder](..\README.md).
+
+Place the resulting 'deploymentVariables.json' file within the ./src/bicep/examples folder.
+
+### Deploying IaaS DNS Forwarders
+
+Connect to the appropriate Azure Environment and set appropriate context, see getting started with Azure PowerShell for help if needed.  The commands below assume you are deploying in Azure Government and show the entire process from deploying MLZ and then adding DNS forwarders post-deployment.
+
+```PowerShell
+cd .\src\bicep
+Connect-AzAccount -Environment AzureUSGovernment
+New-AzSubscriptionDeployment -Name contoso -TemplateFile .\mlz.bicep -resourcePrefix 'contoso' -Location 'USGovVirginia'
+cd .\examples
+(Get-AzSubscriptionDeployment -Name contoso).outputs | ConvertTo-Json | Out-File -FilePath .\deploymentVariables.json
+cd .\keyVault
+New-AzResourceGroupDeployment -DeploymentName IaaSDNSForwarders `
+                              -TemplateFile .\forwarderVm.bicep
+                              -ResourceGroupName 'contoso-rg-hub-mlz'
+                              -vmNamePrefix 'contoso-dnsfwd'
+                              -nicPrivateIPAddresses "10.9.0.4", "10.9.0.5"
+                              -dnsServerForwardersIpAddresses "2.2.2.2"                 
+```
+
+### Setting all Virtual Networks to use the Forwarders as DNS servers
+
+The PowerShell script below configures the (existing) Virtual Networks to use the DNS Forwarders as DNS servers.
+
+```PowerShell
+$dnsForwarders = "10.9.0.4", "10.9.0.5"
+$virtualNetworks = Get-AzVirtualNetwork
+foreach($vnet in $virtualnetworks){
+    Write-Output ("Changing VNET " + [char]34 + $vnet.Name + [char]34 + " DNS Servers...")
+    $vnet.DhcpOptions.DnsServers = $dnsForwarders
+    $vnetSave = $vnet | Set-AzVirtualNetwork
+}
+```
+

src/bicep/examples/iaas-dns-forwarders/extensions/Set-ConditionalDnsForwarders.ps1

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+# Script to set Windows DNS Server Conditional DNS Forwarders
+[CmdletBinding()]
+param (
+    [Parameter(Position = 0,
+        HelpMessage = "JSON Array of DNS Conditional Forwarders to configure",
+        Mandatory = $true)]
+    [String]
+    $ConditionalDnsForwardersJSON
+)
+
+# Convert from JSON
+$conditionalDnsForwarders = $ConditionalDnsForwardersJSON | ConvertFrom-Json
+if (!($conditionalDnsForwarders)) { throw("Could not convert from JSON:`r`n" + $ConditionalDnsForwardersJSON) }
+
+# Loop through conditional forwarders
+foreach ($conditionalDnsForwarder in $conditionalDnsForwarders) {
+    # Get existing zone
+    $existingZone = Get-DnsServerZone -Name $conditionalDnsForwarder.Name -ErrorAction:SilentlyContinue
+    if ($existingZone) {Write-Output ("Found existing zone for " + [char]34 + $conditionalDnsForwarder.Name + [char]34 + "...")}
+    # Create conditional forwarder
+    else {
+        Add-DnsServerConditionalForwarderZone -Name $conditionalDnsForwarder.Name -MasterServers $conditionalDnsForwarder.Forwarders
+        # Verify forwarder was created
+        $fwdGet = Get-DnsServerZone -Name $conditionalDnsForwarder.Name -ErrorAction:SilentlyContinue
+        if ($fwdGet) {
+            Write-Output ([char]34 + $conditionalDnsForwarder.Name + [char]34 + " was successfully created...")
+        }   
+        else{throw("Could not create Conditional DNS Forwarder for name " + [char]34 + $conditionalDnsForwarder.Name + [char]34 + ".")}
+    }
+}