Step-by-Step: User-Defined Routing in the Cloud with Azure Resource Manager and Azure PowerShell 1.0 Preview

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Custom IP routing topologies on Azure Virtual Networks have been available for several months via native User-Defined Routing (UDR) and IP Forwarding features.  However, recently I’ve been receiving questions on how to configure IP forwarding and user-defined routes via the new Azure Resource Manager (ARM) API. 

Azure UDR 2

In this article, we’ll step through a set of PowerShell snippets that walk-through the entire end-to-end process of using the new Azure PowerShell 1.0 Preview module cmdlets for ARM to implement user-defined routing for the front-end subnet pictured above.

# Sign-in with Azure account credentials

Login-AzureRmAccount

# Select Azure Subscription

$subscriptionId =
(Get-AzureRmSubscription |
Out-GridView `
-Title "Select an Azure Subscription ..." `
-PassThru).SubscriptionId

Select-AzureRmSubscription `
-SubscriptionId $subscriptionId

# First time only - register ARM core resource providers

Register-AzureRmResourceProvider `
-ProviderNamespace Microsoft.Compute

Register-AzureRmResourceProvider `
-ProviderNamespace Microsoft.Storage

Register-AzureRmResourceProvider `
-ProviderNamespace Microsoft.Network

Get-AzureRmResourceProvider |
Select-Object `
-Property ProviderNamespace `
-ExpandProperty ResourceTypes

# Select Resource Group in which existing VNET is provisioned

$rgName =
(Get-AzureRmResourceGroup |
Out-GridView `
-Title "Select an Azure Resource Group ..." `
-PassThru).ResourceGroupName

# Select Azure VNET and Location on which to enable UDR

$vnetName =
(Get-AzureRmVirtualNetwork `
-ResourceGroupName $rgName).Name |
Out-GridView `
-Title "Select an Azure VNET ..." `
-PassThru

$vnet = Get-AzureRmVirtualNetwork `
-ResourceGroupName $rgName `
-Name $vnetName

$location = $vnet.Location

# Select Azure Subnet on which to enable UDR

$subnetName =
$vnet.Subnets.Name |
Out-GridView `
-Title "Select an Azure Subnet ..." `
-PassThru

$subnet = $vnet.Subnets |
Where-Object Name -eq $subnetName

# Create new UDR table

$routeTableName = "frontendroutetable"

$routeTable = New-AzureRmRouteTable `
-Name $routeTableName `
-ResourceGroupName $rgName `
-Location $location

# Add a route to the UDR Table

$routeName = "frontendroute"

$routeTable |
Add-AzureRmRouteConfig `
-Name $routeName `
-AddressPrefix "192.168.2.0/24" `
-NextHopType VirtualAppliance `
-NextHopIpAddress "192.168.0.101" |
Set-AzureRmRouteTable

# Assign UDR table to selected subnet

Set-AzureRmVirtualNetworkSubnetConfig `
-VirtualNetwork $vnet `
-Name $subnetName `
-AddressPrefix $subnet.AddressPrefix `
-RouteTableId $routeTable.Id |
Set-AzureRmVirtualNetwork

# Confirm UDR table is provisioned and assigned to subnet

Get-AzureRmRouteTable `
-ResourceGroupName $rgName `
-Name $routeTableName

# Configure “Appliance” VM for IP Forwarding on each NIC

$vmName =
(Get-AzureRmVM -ResourceGroupName $rgName).Name |
Out-GridView `
-Title "Select a VM to configure forwarding ..." `
-PassThru

$nicName =
((Get-AzureRmVM `
-ResourceGroupName $rgName `
-Name $vmName).NetworkInterfaceIDs).Split("/")[-1] |
Out-GridView `
-Title "Select a NIC to configure forwarding ..." `
-PassThru

$nicConfig =
Get-AzureRmNetworkInterface `
-ResourceGroupName $rgName `
-Name $nicName

$nicConfig.EnableIPForwarding = $true

$nicConfig | Set-AzureRmNetworkInterface

See you in the Clouds!

- Keith