Configure a VNet-to-VNet connection for the classic deployment model

This article walks you through the steps to create and connect virtual networks together using the classic deployment model (also known as Service Management). The following steps use the Azure classic portal to create the VNets and gateways, and PowerShell to configure the VNet-to-VNet connection. You cannot configure the connection in the portal.

VNet to VNet Connectivity Diagram

Deployment models and methods for VNet-to-VNet connections

It's important to understand that Azure currently works with two deployment models: Resource Manager and classic. Before beginning your configuration, verify that you are using the instructions for the deployment model that you want to work in. For more information, see Understanding deployment models.

The following table shows the currently available deployment models and methods for VNet-to-VNet configurations. When an article with configuration steps is available, we link directly to it from this table.

Deployment Model/Method Azure Portal Classic Portal PowerShell
Classic Not Supported Article* Supported
Resource Manager Article+ Not Supported Article
Connections between different deployment models Article* Supported* Article

(+) denotes this deployment method is available only for VNets in the same subscription.
(*) denotes that this deployment method also requires PowerShell.

About VNet-to-VNet connections

Connecting a virtual network to another virtual network (VNet-to-VNet) is similar to connecting a virtual network to an on-premises site location. Both connectivity types use a VPN gateway to provide a secure tunnel using IPsec/IKE.

The VNets you connect can be in different subscriptions and different regions. You can combine VNet to VNet communication with multi-site configurations. This lets you establish network topologies that combine cross-premises connectivity with inter-virtual network connectivity.

Why connect virtual networks?

You may want to connect virtual networks for the following reasons:

  • Cross region geo-redundancy and geo-presence

    • You can set up your own geo-replication or synchronization with secure connectivity without going over Internet-facing endpoints.
    • With Azure Load Balancer and Microsoft or third-party clustering technology, you can set up highly available workload with geo-redundancy across multiple Azure regions. One important example is to set up SQL Always On with Availability Groups spreading across multiple Azure regions.
  • Regional multi-tier applications with strong isolation boundary

    • Within the same region, you can set up multi-tier applications with multiple VNets connected together with strong isolation and secure inter-tier communication.
  • Cross subscription, inter-organization communication in Azure

    • If you have multiple Azure subscriptions, you can connect workloads from different subscriptions together securely between virtual networks.
    • For enterprises or service providers, you can enable cross-organization communication with secure VPN technology within Azure.

VNet-to-VNet considerations for classic VNets

  • The virtual networks can be in the same or different subscriptions.
  • The virtual networks can be in the same or different Azure regions (locations).
  • A cloud service or a load balancing endpoint can't span across virtual networks, even if they are connected together.
  • Connecting multiple virtual networks together doesn't require any VPN devices.
  • VNet-to-VNet supports connecting Azure Virtual Networks. It does not support connecting virtual machines or cloud services that are not deployed to a virtual network.
  • VNet-to-VNet requires dynamic routing gateways. Azure static routing gateways are not supported.
  • Virtual network connectivity can be used simultaneously with multi-site VPNs. There is a maximum of 10 VPN tunnels for a virtual network VPN gateway connecting to either other virtual networks, or on-premises sites.
  • The address spaces of the virtual networks and on-premises local network sites must not overlap. Overlapping address spaces will cause the creation of virtual networks or uploading netcfg configuration files to fail.
  • Redundant tunnels between a pair of virtual networks are not supported.
  • All VPN tunnels for the VNet, including P2S VPNs, share the available bandwidth for the VPN gateway, and the same VPN gateway uptime SLA in Azure.
  • VNet-to-VNet traffic travels across the Azure backbone.

Step 1 - Plan your IP address ranges

It’s important to decide the ranges that you’ll use to configure your virtual networks. For this configuration, you must make sure that none of your VNet ranges overlap with each other, or with any of the local networks that they connect to.

The following table shows an example of how to define your VNets. Use the ranges as a guideline only. Write down the ranges for your virtual networks. You need this information for later steps.

Example settings

Virtual Network Address Space Region Connects to local network site
VNet1 VNet1 (10.1.0.0/16) US West VNet2Local (10.2.0.0/16)
VNet2 VNet2 (10.2.0.0/16) Japan East VNet1Local (10.1.0.0/16)

Step 2 - Create VNet1

In this step, we create VNet1. When using any of the examples, be sure to substitute your own values. If your VNet already exists, you don't need to do this step. But, you do need to verify that the IP address ranges don't overlap with the ranges for your second VNet, or with any of the other VNets to which you want to connect.

  1. Log in to the Azure classic portal. In this article, we use the classic portal because some of the required configuration settings are not yet available in the Azure portal.
  2. In the lower left-hand corner of the screen, click New > Network Services > Virtual Network > Custom Create to begin the configuration wizard. As you navigate through the wizard, add the specified values to each page.

Virtual Network Details

On the Virtual Network Details page, enter the following information:

Virtual Network Details

  • Name - Name your virtual network. For example, VNet1.
  • Location – When you create a virtual network, you associate it with an Azure location (region). For example, if you want your VMs that are deployed to your virtual network to be physically located in West US, select that location. You can’t change the location associated with your virtual network after you create it.

DNS Servers and VPN Connectivity

On the DNS Servers and VPN Connectivity page, enter the following information, and then click the next arrow on the lower right.

DNS Servers and VPN Connectivity

  • DNS Servers - Enter the DNS server name and IP address, or select a previously registered DNS server from the dropdown. This setting does not create a DNS server. It allows you to specify the DNS servers that you want to use for name resolution for this virtual network. If you want to have name resolution between your virtual networks, you have to configure your own DNS server, rather than using the name resolution that is provided by Azure.
  • Don’t select any of the checkboxes for P2S or S2S connectivity. Click the arrow on the lower right to move to the next screen.

Virtual Network Address Spaces

On the Virtual Network Address Spaces page, specify the address range that you want to use for your virtual network. These are the dynamic IP addresses (DIPS) that will be assigned to the VMs and other role instances that you deploy to this virtual network.

If you are creating a VNet that will also have a connection to your on-premises network, it's especially important to select a range that does not overlap with any of the ranges that are used for your on-premises network. In that case, you need to coordinate with your network administrator. Your network administrator may need to carve out a range of IP addresses from your on-premises network address space for you to use for your VNet.

Virtual Network Address Spaces page

  • Address Space - including Starting IP and Address Count. Verify that the address spaces you specify don’t overlap with any of the address spaces that you have on your on-premises network. For this example, we use 10.1.0.0/16 for VNet1.
  • Add subnet - including Starting IP and Address Count. Additional subnets are not required, but you may want to create a separate subnet for VMs that will have static DIPS. Or you might want to have your VMs in a subnet that is separate from your other role instances.

Click the checkmark on the lower right of the page and your virtual network will begin to create. When it completes, you will see "Created" listed under Status on the Networks page.

Step 3 - Create VNet2

Next, repeat the preceding steps to create another VNet. In later steps, you will connect the two VNets. You can refer to the example settings in Step 1. If your VNet already exists, you don't need to do this step. However, you need to verify that the IP address ranges don't overlap with any of the other VNets or on-premises networks that you want to connect to.

Step 4 - Add the local network sites

When you create a VNet-to-VNet configuration, you need to configure local network sites, which are shown in the Local Networks page of the portal. Azure uses the settings specified in each local network site to determine how to route traffic between the VNets. You determine the name you want to use to refer to each local network site. It's best to use something descriptive, as you select the value from a dropdown list in later steps.

For example, VNet1 connects to a local network site that you create named "VNet2Local". The settings for VNet2Local contain the address prefixes for VNet2, and a public IP address for the VNet2 gateway. VNet2 connects to a local network site you create named "VNet1Local" that contains the address prefixes for VNet1 and the public IP address for the VNet1 gateway.

Add the local network site VNet1Local

  1. In the lower left-hand corner of the screen, click New > Network Services > Virtual Network > Add Local Network.
  2. On the Specify your local network details page, for Name, enter a name that you want to use to represent the network that you want to connect to. In this example, you can use "VNet1Local" to refer to the IP address ranges and gateway for VNet1.
  3. For VPN Device IP address (optional), specify any valid public IP address. Typically, you’d use the actual external IP address for a VPN device. For VNet-to-VNet configurations, you use the public IP address that is assigned to the gateway for your VNet. But, given that you’ve not yet created the gateway, you can specify any valid public IP address as a placeholder. Don't leave this blank - it's not optional for this configuration. In a later step, you go back into these settings and configure them with the corresponding gateway IP addresses once Azure generates it. Click the arrow to advance to the next screen.
  4. On the Specify the address page, enter the IP address range and address count for VNet1. This must correspond exactly to the range that is configured for VNet1. Azure uses the IP address ranges that you specify to route the traffic intended for VNet1. Click the checkmark to create the local network.

Add the local network site VNet2Local

Use the steps above to create the local network site "VNet2Local". You can refer to the values in the example settings in Step 1, if necessary.

Configure each VNet to point to a local network

Each VNet must point to the respective local network that you want to route traffic to.

For VNet1

  1. Navigate to the Configure page for virtual network VNet1.
  2. Under site-to-site connectivity, select "Connect to the local network", and then select VNet2Local as the local network from the dropdown.
  3. Save your settings.

For VNet2

  1. Navigate to the Configure page for virtual network VNet2.
  2. Under site-to-site connectivity, select "Connect to the local network", then select VNet1Local from the dropdown as the local network.
  3. Save your settings.

Step 5 - Configure a gateway for each VNet

Configure a Dynamic Routing gateway for each virtual network. This configuration does not support Static Routing gateways. If you are using VNets that were previously configured and that already have Dynamic Routing gateways, you don't need to do this step. If your gateways are Static Routing, you need to delete them and recreate them as Dynamic Routing gateways. If you delete a gateway, the public IP address assigned to it gets released, and you need to go back and reconfigure any of your local networks and VPN devices with the new public IP address for the new gateway.

  1. On the Networks page, verify that the status column for your virtual network is Created.
  2. In the Name column, click the name of your virtual network. For this example, we use "VNet1".
  3. On the Dashboard page, notice that this VNet doesn’t have a gateway configured yet. You’ll see this status change as you go through the steps to configure your gateway.
  4. At the bottom of the page, click Create Gateway and Dynamic Routing. When the system prompts you to confirm that you want the gateway created, click Yes.

    Gateway type

  5. When your gateway is creating, notice the gateway graphic on the page changes to yellow and says "Creating Gateway". It typically takes about 30 minutes for the gateway to create.
  6. Repeat the same steps for VNet2. You don’t need the first VNet gateway to complete before you begin to create the gateway for your other VNet.
  7. When the gateway status changes to "Connecting", the public IP address for each gateway is visible in the Dashboard. Write down the IP address that corresponds to each VNet, taking care not to mix them up. These are the IP addresses that are used when you edit your placeholder IP addresses for the VPN Device for each local network.

Step 6 - Edit the local network

  1. On the Local Networks page, click the name of the Local Network name that you want to edit, then click Edit at the bottom of the page. For VPN Device IP address, input the IP address of the gateway that corresponds to the VNet. For example, for VNet1Local, put in the gateway IP address assigned to VNet1. Then click the arrow at the bottom of the page.
  2. On the Specify the address space page, click the checkmark on the lower right without making any changes.

Step 7 - Create the VPN connection

When all the previous steps have been completed, set the IPsec/IKE pre-shared keys and create the connection. This set of steps uses PowerShell and cannot be configured in the portal. See How to install and configure Azure PowerShell for more information about installing the Azure PowerShell cmdlets. Make sure to download the latest version of the Service Management (SM) cmdlets.

  1. Open Windows PowerShell and log in.

     Add-AzureAccount
    
  2. Select the subscription that your VNets reside in.

     Get-AzureSubscription | Sort SubscriptionName | Select SubscriptionName
     Select-AzureSubscription -SubscriptionName "<Subscription Name>"
    
  3. Create the connections. In the examples, notice that the shared key is exactly the same. The shared key must always match.

    VNet1 to VNet2 connection

     Set-AzureVNetGatewayKey -VNetName VNet1 -LocalNetworkSiteName VNet2Local -SharedKey A1b2C3D4
    

    VNet2 to VNet1 connection

     Set-AzureVNetGatewayKey -VNetName VNet2 -LocalNetworkSiteName VNet1Local -SharedKey A1b2C3D4
    
  4. Wait for the connections to initialize. Once the gateway has initialized, the gateway looks like the following graphic.

    Gateway Status - Connected

Important

When working with gateway subnets, avoid associating a network security group (NSG) to the gateway subnet. Associating a network security group to this subnet may cause your VPN gateway to stop functioning as expected. For more information about network security groups, see What is a network security group?

Next steps

You can add virtual machines to your virtual networks. See the Virtual Machines documentation for more information.