Forced tunneling lets you redirect or "force" all Internet-bound traffic back to your on-premises location via a Site-to-Site VPN tunnel for inspection and auditing. This is a critical security requirement for most enterprise IT policies. Without forced tunneling, Internet-bound traffic from your VMs in Azure always traverses from Azure network infrastructure directly out to the Internet, without the option to allow you to inspect or audit the traffic. Unauthorized Internet access can potentially lead to information disclosure or other types of security breaches.
Azure currently works with two deployment models: Resource Manager and classic. The two models are not completely compatible with each other. Before you begin, you need to know which model that you want to work in. For information about the deployment models, see Understanding deployment models. If you are new to Azure, we recommend that you use the Resource Manager deployment model.
This article walks you through configuring forced tunneling for virtual networks created using the Resource Manager deployment model. Forced tunneling can be configured by using PowerShell, not through the portal. If you want to configure forced tunneling for the classic deployment model, select classic article from the following dropdown list:
About forced tunneling
The following diagram illustrates how forced tunneling works.
In the example above, the Frontend subnet is not forced tunneled. The workloads in the Frontend subnet can continue to accept and respond to customer requests from the Internet directly. The Mid-tier and Backend subnets are forced tunneled. Any outbound connections from these two subnets to the Internet will be forced or redirected back to an on-premises site via one of the S2S VPN tunnels.
This allows you to restrict and inspect Internet access from your virtual machines or cloud services in Azure, while continuing to enable your multi-tier service architecture required. If there are no Internet-facing workloads in your virtual networks, you also can apply forced tunneling to the entire virtual networks.
Requirements and considerations
Forced tunneling in Azure is configured via virtual network user-defined routes. Redirecting traffic to an on-premises site is expressed as a Default Route to the Azure VPN gateway. For more information about user-defined routing and virtual networks, see User-defined routes and IP forwarding.
Each virtual network subnet has a built-in, system routing table. The system routing table has the following three groups of routes:
- Local VNet routes: Directly to the destination VMs in the same virtual network.
- On-premises routes: To the Azure VPN gateway.
- Default route: Directly to the Internet. Packets destined to the private IP addresses not covered by the previous two routes are dropped.
- This procedure uses user-defined routes (UDR) to create a routing table to add a default route, and then associate the routing table to your VNet subnet(s) to enable forced tunneling on those subnets.
- Forced tunneling must be associated with a VNet that has a route-based VPN gateway. You need to set a "default site" among the cross-premises local sites connected to the virtual network. Also, the on-premises VPN device must be configured using 0.0.0.0/0 as traffic selectors.
- ExpressRoute forced tunneling is not configured via this mechanism, but instead, is enabled by advertising a default route via the ExpressRoute BGP peering sessions. For more information, see the ExpressRoute Documentation.
The following procedure helps you create a resource group and a VNet. You'll then create a VPN gateway and configure forced tunneling. In this procedure, the virtual network 'MultiTier-VNet' has three subnets: 'Frontend', 'Midtier', and 'Backend', with four cross-premises connections: 'DefaultSiteHQ', and three Branches.
The procedure steps set the 'DefaultSiteHQ' as the default site connection for forced tunneling, and configure the 'Midtier' and 'Backend' subnets to use forced tunneling.
Before you begin
Install the latest version of the Azure Resource Manager PowerShell cmdlets. See How to install and configure Azure PowerShell for more information about installing the PowerShell cmdlets.
To log in
Before beginning this configuration, you must log in to your Azure account. The cmdlet prompts you for the login credentials for your Azure account. After logging in, it downloads your account settings so they are available to Azure PowerShell. For more information, see Using Windows PowerShell with Resource Manager.
To log in, open your PowerShell console with elevated privileges, and connect to your account. Use the following example to help you connect:
If you have multiple Azure subscriptions, check the subscriptions for the account.
Specify the subscription that you want to use.
Select-AzureRmSubscription -SubscriptionName "Replace_with_your_subscription_name"
Configure forced tunneling
Create a resource group.
New-AzureRmResourceGroup -Name 'ForcedTunneling' -Location 'North Europe'
Create a virtual network and specify subnets.
$s1 = New-AzureRmVirtualNetworkSubnetConfig -Name "Frontend" -AddressPrefix "10.1.0.0/24" $s2 = New-AzureRmVirtualNetworkSubnetConfig -Name "Midtier" -AddressPrefix "10.1.1.0/24" $s3 = New-AzureRmVirtualNetworkSubnetConfig -Name "Backend" -AddressPrefix "10.1.2.0/24" $s4 = New-AzureRmVirtualNetworkSubnetConfig -Name "GatewaySubnet" -AddressPrefix "10.1.200.0/28" $vnet = New-AzureRmVirtualNetwork -Name "MultiTier-VNet" -Location "North Europe" -ResourceGroupName "ForcedTunneling" -AddressPrefix "10.1.0.0/16" -Subnet $s1,$s2,$s3,$s4
Create the local network gateways.
$lng1 = New-AzureRmLocalNetworkGateway -Name "DefaultSiteHQ" -ResourceGroupName "ForcedTunneling" -Location "North Europe" -GatewayIpAddress "126.96.36.199" -AddressPrefix "192.168.1.0/24" $lng2 = New-AzureRmLocalNetworkGateway -Name "Branch1" -ResourceGroupName "ForcedTunneling" -Location "North Europe" -GatewayIpAddress "188.8.131.52" -AddressPrefix "192.168.2.0/24" $lng3 = New-AzureRmLocalNetworkGateway -Name "Branch2" -ResourceGroupName "ForcedTunneling" -Location "North Europe" -GatewayIpAddress "184.108.40.206" -AddressPrefix "192.168.3.0/24" $lng4 = New-AzureRmLocalNetworkGateway -Name "Branch3" -ResourceGroupName "ForcedTunneling" -Location "North Europe" -GatewayIpAddress "220.127.116.11" -AddressPrefix "192.168.4.0/24"
Create the route table and route rule.
New-AzureRmRouteTable –Name "MyRouteTable" -ResourceGroupName "ForcedTunneling" –Location "North Europe" $rt = Get-AzureRmRouteTable –Name "MyRouteTable" -ResourceGroupName "ForcedTunneling" Add-AzureRmRouteConfig -Name "DefaultRoute" -AddressPrefix "0.0.0.0/0" -NextHopType VirtualNetworkGateway -RouteTable $rt Set-AzureRmRouteTable -RouteTable $rt
Associate the route table to the Midtier and Backend subnets.
$vnet = Get-AzureRmVirtualNetwork -Name "MultiTier-Vnet" -ResourceGroupName "ForcedTunneling" Set-AzureRmVirtualNetworkSubnetConfig -Name "MidTier" -VirtualNetwork $vnet -AddressPrefix "10.1.1.0/24" -RouteTable $rt Set-AzureRmVirtualNetworkSubnetConfig -Name "Backend" -VirtualNetwork $vnet -AddressPrefix "10.1.2.0/24" -RouteTable $rt Set-AzureRmVirtualNetwork -VirtualNetwork $vnet
Create the Gateway with a default site. This step takes some time to complete, sometimes 45 minutes or more, because you are creating and configuring the gateway.
The -GatewayDefaultSite is the cmdlet parameter that allows the forced routing configuration to work, so take care to configure this setting properly. This parameter is available in PowerShell 1.0 or later.
$pip = New-AzureRmPublicIpAddress -Name "GatewayIP" -ResourceGroupName "ForcedTunneling" -Location "North Europe" -AllocationMethod Dynamic $gwsubnet = Get-AzureRmVirtualNetworkSubnetConfig -Name "GatewaySubnet" -VirtualNetwork $vnet $ipconfig = New-AzureRmVirtualNetworkGatewayIpConfig -Name "gwIpConfig" -SubnetId $gwsubnet.Id -PublicIpAddressId $pip.Id New-AzureRmVirtualNetworkGateway -Name "Gateway1" -ResourceGroupName "ForcedTunneling" -Location "North Europe" -IpConfigurations $ipconfig -GatewayType Vpn -VpnType RouteBased -GatewaySku VpnGw1 -GatewayDefaultSite $lng1 -EnableBgp $false
Establish the Site-to-Site VPN connections.
$gateway = Get-AzureRmVirtualNetworkGateway -Name "Gateway1" -ResourceGroupName "ForcedTunneling" $lng1 = Get-AzureRmLocalNetworkGateway -Name "DefaultSiteHQ" -ResourceGroupName "ForcedTunneling" $lng2 = Get-AzureRmLocalNetworkGateway -Name "Branch1" -ResourceGroupName "ForcedTunneling" $lng3 = Get-AzureRmLocalNetworkGateway -Name "Branch2" -ResourceGroupName "ForcedTunneling" $lng4 = Get-AzureRmLocalNetworkGateway -Name "Branch3" -ResourceGroupName "ForcedTunneling" New-AzureRmVirtualNetworkGatewayConnection -Name "Connection1" -ResourceGroupName "ForcedTunneling" -Location "North Europe" -VirtualNetworkGateway1 $gateway -LocalNetworkGateway2 $lng1 -ConnectionType IPsec -SharedKey "preSharedKey" New-AzureRmVirtualNetworkGatewayConnection -Name "Connection2" -ResourceGroupName "ForcedTunneling" -Location "North Europe" -VirtualNetworkGateway1 $gateway -LocalNetworkGateway2 $lng2 -ConnectionType IPsec -SharedKey "preSharedKey" New-AzureRmVirtualNetworkGatewayConnection -Name "Connection3" -ResourceGroupName "ForcedTunneling" -Location "North Europe" -VirtualNetworkGateway1 $gateway -LocalNetworkGateway2 $lng3 -ConnectionType IPsec -SharedKey "preSharedKey" New-AzureRmVirtualNetworkGatewayConnection -Name "Connection4" -ResourceGroupName "ForcedTunneling" -Location "North Europe" -VirtualNetworkGateway1 $gateway -LocalNetworkGateway2 $lng4 -ConnectionType IPsec -SharedKey "preSharedKey" Get-AzureRmVirtualNetworkGatewayConnection -Name "Connection1" -ResourceGroupName "ForcedTunneling"