Tutorial: Connect a virtual network to an ExpressRoute circuit

This article helps you link virtual networks (VNets) to Azure ExpressRoute circuits by using the Resource Manager deployment model and PowerShell. Virtual networks can either be in the same subscription or part of another subscription. This article also shows you how to update a virtual network link.

  • You can link up to 10 virtual networks to a standard ExpressRoute circuit. All virtual networks must be in the same geopolitical region when using a standard ExpressRoute circuit.

  • A single VNet can be linked to up to 16 ExpressRoute circuits. Use the steps in this article to create a new connection object for each ExpressRoute circuit you're connecting to. The ExpressRoute circuits can be in the same subscription, different subscriptions, or a mix of both.

  • If you enable the ExpressRoute premium add-on, you can link virtual networks outside of the geopolitical region of the ExpressRoute circuit. The premium add-on will also allow you to connect more than 10 virtual networks to your ExpressRoute circuit depending on the bandwidth chosen. Check the FAQ for more details on the premium add-on.

  • In order to create the connection from the ExpressRoute circuit to the target ExpressRoute virtual network gateway, the number of address spaces advertised from the local or peered virtual networks needs to be equal to or less than 200. Once the connection has been successfully created, you can add additional address spaces, up to 1,000, to the local or peered virtual networks.

In this tutorial, you learn how to:

  • Connect a virtual network in the same subscription to a circuit
  • Connect a virtual network in a different subscription to a circuit
  • Modify a virtual network connection
  • Configure ExpressRoute FastPath

Prerequisites

  • Review the prerequisites, routing requirements, and workflows before you begin configuration.

  • You must have an active ExpressRoute circuit.

    • Follow the instructions to create an ExpressRoute circuit and have the circuit enabled by your connectivity provider.
    • Ensure that you have Azure private peering configured for your circuit. See the configure routing article for routing instructions.
    • Ensure that Azure private peering gets configured and establishes BGP peering between your network and Microsoft for end-to-end connectivity.
    • Ensure that you have a virtual network and a virtual network gateway created and fully provisioned. Follow the instructions to create a virtual network gateway for ExpressRoute. A virtual network gateway for ExpressRoute uses the GatewayType 'ExpressRoute', not VPN.

Working with Azure PowerShell

The steps and examples in this article use Azure PowerShell Az modules. To install the Az modules locally on your computer, see Install Azure PowerShell. To learn more about the new Az module, see Introducing the new Azure PowerShell Az module. PowerShell cmdlets are updated frequently. If you are not running the latest version, the values specified in the instructions may fail. To find the installed versions of PowerShell on your system, use the Get-Module -ListAvailable Az cmdlet.

You can use Azure Cloud Shell to run most PowerShell cmdlets and CLI commands, instead of installing Azure PowerShell or CLI locally. Azure Cloud Shell is a free interactive shell that has common Azure tools preinstalled and is configured to use with your account. To run any code contained in this article on Azure Cloud Shell, open a Cloud Shell session, use the Copy button on a code block to copy the code, and paste it into the Cloud Shell session with Ctrl+Shift+V on Windows and Linux, or Cmd+Shift+V on macOS. Pasted text is not automatically executed, press Enter to run code.

There are a few ways to launch the Cloud Shell:

Option Link
Click Try It in the upper right corner of a code block. Cloud Shell in this article
Open Cloud Shell in your browser. https://shell.azure.com/powershell
Click the Cloud Shell button on the menu in the upper right of the Azure portal. Cloud Shell in the portal

Connect a virtual network in the same subscription to a circuit

You can connect a virtual network gateway to an ExpressRoute circuit by using the following cmdlet. Make sure that the virtual network gateway is created and is ready for linking before you run the cmdlet:

$circuit = Get-AzExpressRouteCircuit -Name "MyCircuit" -ResourceGroupName "MyRG"
$gw = Get-AzVirtualNetworkGateway -Name "ExpressRouteGw" -ResourceGroupName "MyRG"
$connection = New-AzVirtualNetworkGatewayConnection -Name "ERConnection" -ResourceGroupName "MyRG" -Location "East US" -VirtualNetworkGateway1 $gw -PeerId $circuit.Id -ConnectionType ExpressRoute

Connect a virtual network in a different subscription to a circuit

You can share an ExpressRoute circuit across multiple subscriptions. The following figure shows a simple schematic of how sharing works for ExpressRoute circuits across multiple subscriptions.

Note

Connecting virtual networks between Azure sovereign clouds and Public Azure cloud is not supported. You can only link virtual networks from different subscriptions in the same cloud.

Each of the smaller clouds within the large cloud is used to represent subscriptions that belong to different departments within an organization. Each of the departments within the organization uses their own subscription for deploying their services--but they can share a single ExpressRoute circuit to connect back to your on-premises network. A single department (in this example: IT) can own the ExpressRoute circuit. Other subscriptions within the organization may use the ExpressRoute circuit.

Note

Connectivity and bandwidth charges for the ExpressRoute circuit will be applied to the subscription owner. All virtual networks share the same bandwidth.

Cross-subscription connectivity

Administration - circuit owners and circuit users

The 'circuit owner' is an authorized Power User of the ExpressRoute circuit resource. The circuit owner can create authorizations that can be redeemed by 'circuit users'. Circuit users are owners of virtual network gateways that aren't within the same subscription as the ExpressRoute circuit. Circuit users can redeem authorizations (one authorization per virtual network).

The circuit owner has the power to modify and revoke authorizations at any time. Revoking an authorization results in all link connections being deleted from the subscription whose access was revoked.

Circuit owner operations

To create an authorization

The circuit owner creates an authorization, which creates an authorization key to be used by a circuit user to connect their virtual network gateways to the ExpressRoute circuit. An authorization is valid for only one connection.

The following cmdlet snippet shows how to create an authorization:

$circuit = Get-AzExpressRouteCircuit -Name "MyCircuit" -ResourceGroupName "MyRG"
Add-AzExpressRouteCircuitAuthorization -ExpressRouteCircuit $circuit -Name "MyAuthorization1"
Set-AzExpressRouteCircuit -ExpressRouteCircuit $circuit

$circuit = Get-AzExpressRouteCircuit -Name "MyCircuit" -ResourceGroupName "MyRG"
$auth1 = Get-AzExpressRouteCircuitAuthorization -ExpressRouteCircuit $circuit -Name "MyAuthorization1"

The response to the previous commands will contain the authorization key and status:

Name                   : MyAuthorization1
Id                     : /subscriptions/&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&/resourceGroups/ERCrossSubTestRG/providers/Microsoft.Network/expressRouteCircuits/CrossSubTest/authorizations/MyAuthorization1
Etag                   : &&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&& 
AuthorizationKey       : ####################################
AuthorizationUseStatus : Available
ProvisioningState      : Succeeded

To review authorizations

The circuit owner can review all authorizations that are issued on a particular circuit by running the following cmdlet:

$circuit = Get-AzExpressRouteCircuit -Name "MyCircuit" -ResourceGroupName "MyRG"
$authorizations = Get-AzExpressRouteCircuitAuthorization -ExpressRouteCircuit $circuit

To add authorizations

The circuit owner can add authorizations by using the following cmdlet:

$circuit = Get-AzExpressRouteCircuit -Name "MyCircuit" -ResourceGroupName "MyRG"
Add-AzExpressRouteCircuitAuthorization -ExpressRouteCircuit $circuit -Name "MyAuthorization2"
Set-AzExpressRouteCircuit -ExpressRouteCircuit $circuit

$circuit = Get-AzExpressRouteCircuit -Name "MyCircuit" -ResourceGroupName "MyRG"
$authorizations = Get-AzExpressRouteCircuitAuthorization -ExpressRouteCircuit $circuit

To delete authorizations

The circuit owner can revoke/delete authorizations to the user by running the following cmdlet:

Remove-AzExpressRouteCircuitAuthorization -Name "MyAuthorization2" -ExpressRouteCircuit $circuit
Set-AzExpressRouteCircuit -ExpressRouteCircuit $circuit

Circuit user operations

The circuit user needs the peer ID and an authorization key from the circuit owner. The authorization key is a GUID.

Peer ID can be checked from the following command:

Get-AzExpressRouteCircuit -Name "MyCircuit" -ResourceGroupName "MyRG"

To redeem a connection authorization

The circuit user can run the following cmdlet to redeem a link authorization:

$id = "/subscriptions/********************************/resourceGroups/ERCrossSubTestRG/providers/Microsoft.Network/expressRouteCircuits/MyCircuit"    
$gw = Get-AzVirtualNetworkGateway -Name "ExpressRouteGw" -ResourceGroupName "MyRG"
$connection = New-AzVirtualNetworkGatewayConnection -Name "ERConnection" -ResourceGroupName "RemoteResourceGroup" -Location "East US" -VirtualNetworkGateway1 $gw -PeerId $id -ConnectionType ExpressRoute -AuthorizationKey "^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^"

To release a connection authorization

You can release an authorization by deleting the connection that links the ExpressRoute circuit to the virtual network.

Modify a virtual network connection

You can update certain properties of a virtual network connection.

To update the connection weight

Your virtual network can be connected to multiple ExpressRoute circuits. You may receive the same prefix from more than one ExpressRoute circuit. To choose which connection to send traffic destined for this prefix, you can change RoutingWeight of a connection. Traffic will be sent on the connection with the highest RoutingWeight.

$connection = Get-AzVirtualNetworkGatewayConnection -Name "MyVirtualNetworkConnection" -ResourceGroupName "MyRG"
$connection.RoutingWeight = 100
Set-AzVirtualNetworkGatewayConnection -VirtualNetworkGatewayConnection $connection

The range of RoutingWeight is 0 to 32000. The default value is 0.

Configure ExpressRoute FastPath

You can enable ExpressRoute FastPath if your virtual network gateway is Ultra Performance or ErGw3AZ. FastPath improves data path performance such as packets per second and connections per second between your on-premises network and your virtual network.

Configure FastPath on a new connection

$circuit = Get-AzExpressRouteCircuit -Name "MyCircuit" -ResourceGroupName "MyRG" 
$gw = Get-AzVirtualNetworkGateway -Name "MyGateway" -ResourceGroupName "MyRG" 
$connection = New-AzVirtualNetworkGatewayConnection -Name "MyConnection" -ResourceGroupName "MyRG" -ExpressRouteGatewayBypass -VirtualNetworkGateway1 $gw -PeerId $circuit.Id -ConnectionType ExpressRoute -Location "MyLocation" 

Updating an existing connection to enable FastPath

$connection = Get-AzVirtualNetworkGatewayConnection -Name "MyConnection" -ResourceGroupName "MyRG" 
$connection.ExpressRouteGatewayBypass = $True
Set-AzVirtualNetworkGatewayConnection -VirtualNetworkGatewayConnection $connection

Note

You can use Connection Monitor to verify that your traffic is reaching the destination using FastPath.

Enroll in ExpressRoute FastPath features (preview)

FastPath support for virtual network peering is now in Public preview.

FastPath and virtual network peering

With FastPath and virtual network peering, you can enable ExpressRoute connectivity directly to VMs in a local or peered virtual network, bypassing the ExpressRoute virtual network gateway in the data path.

To enroll in this preview, run the follow Azure PowerShell command in the target Azure subscription:

Register-AzProviderFeature -FeatureName ExpressRouteVnetPeeringGatewayBypass -ProviderNamespace Microsoft.Network

Note

Any connections configured for FastPath in the target subscription will be enrolled in this preview. We do not advise enabling this preview in production subscriptions. If you already have FastPath configured and want to enroll in the preview feature, you need to do the following:

  1. Enroll in the FastPath preview feature with the Azure PowerShell command above.
  2. Disable and then re-enable FastPath on the target connection.

Clean up resources

If you no longer need the ExpressRoute connection, from the subscription where the gateway is located use the Remove-AzVirtualNetworkGatewayConnection command to remove the link between the gateway and the circuit.

Remove-AzVirtualNetworkGatewayConnection "MyConnection" -ResourceGroupName "MyRG"

Next steps

For more information about ExpressRoute, see the ExpressRoute FAQ.