About Azure Virtual WAN
Azure Virtual WAN is a networking service that brings many networking, security, and routing functionalities together to provide a single operational interface. These functionalities include branch connectivity (via connectivity automation from Virtual WAN Partner devices such as SD-WAN or VPN CPE), Site-to-site VPN connectivity, remote user VPN (Point-to-site) connectivity, private (ExpressRoute) connectivity, intra-cloud connectivity (transitive connectivity for virtual networks), VPN ExpressRoute inter-connectivity, routing, Azure Firewall, and encryption for private connectivity. You do not have to have all of these use cases to start using Virtual WAN. You can simply get started with just one use case, and then adjust your network as it evolves.
The Virtual WAN architecture is a hub and spoke architecture with scale and performance built in for branches (VPN/SD-WAN devices), users (Azure VPN/OpenVPN/IKEv2 clients), ExpressRoute circuits, and virtual networks. It enables global transit network architecture, where the cloud hosted network 'hub' enables transitive connectivity between endpoints that may be distributed across different types of 'spokes'.
Azure regions serve as hubs that you can choose to connect to. All hubs are connected in full mesh in a Standard Virtual WAN making it easy for the user to use the Microsoft backbone for any-to-any (any spoke) connectivity. For spoke connectivity with SD-WAN/VPN devices, users can either manually set it up in Azure Virtual WAN, or use the Virtual WAN CPE (SD-WAN/VPN) partner solution to set up connectivity to Azure. We have a list of partners that support connectivity automation (ability to export the device info into Azure, download the Azure configuration and establish connectivity) with Azure Virtual WAN. For more information, see the Virtual WAN partners and locations article.
This article provides a quick view into the network connectivity in Azure Virtual WAN. Virtual WAN offers the following advantages:
- Integrated connectivity solutions in hub and spoke: Automate site-to-site configuration and connectivity between on-premises sites and an Azure hub.
- Automated spoke setup and configuration: Connect your virtual networks and workloads to the Azure hub seamlessly.
- Intuitive troubleshooting: You can see the end-to-end flow within Azure, and then use this information to take required actions.
Basic and Standard virtual WANs
There are two types of virtual WANs: Basic and Standard. The following table shows the available configurations for each type.
|Virtual WAN type||Hub type||Available configurations|
|Basic||Basic||Site-to-site VPN only|
User VPN (P2S)
Inter-hub and VNet-to-VNet transiting through the virtual hub
You can upgrade from Basic to Standard, but cannot revert from Standard back to Basic.
For steps to upgrade a virtual WAN, see Upgrade a virtual WAN from Basic to Standard.
For information about Virtual WAN architecture and how to migrate to Virtual WAN, see the following articles:
Virtual WAN resources
To configure an end-to-end virtual WAN, you create the following resources:
virtualWAN: The virtualWAN resource represents a virtual overlay of your Azure network and is a collection of multiple resources. It contains links to all your virtual hubs that you would like to have within the virtual WAN. Virtual WAN resources are isolated from each other and cannot contain a common hub. Virtual hubs across Virtual WAN do not communicate with each other.
Hub: A virtual hub is a Microsoft-managed virtual network. The hub contains various service endpoints to enable connectivity. From your on-premises network (vpnsite), you can connect to a VPN Gateway inside the virtual hub, connect ExpressRoute circuits to a virtual hub, or even connect mobile users to a Point-to-site gateway in the virtual hub. The hub is the core of your network in a region. There can only be one hub per Azure region.
A hub gateway is not the same as a virtual network gateway that you use for ExpressRoute and VPN Gateway. For example, when using Virtual WAN, you don't create a site-to-site connection from your on-premises site directly to your VNet. Instead, you create a site-to-site connection to the hub. The traffic always goes through the hub gateway. This means that your VNets do not need their own virtual network gateway. Virtual WAN lets your VNets take advantage of scaling easily through the virtual hub and the virtual hub gateway.
Hub virtual network connection: The Hub virtual network connection resource is used to connect the hub seamlessly to your virtual network.
(Preview) Hub-to-Hub connection - Hubs are all connected to each other in a virtual WAN. This implies that a branch, user, or VNet connected to a local hub can communicate with another branch or VNet using the full mesh architecture of the connected hubs. You can also connect VNets within a hub transiting through the virtual hub, as well as VNets across hub, using the hub-to-hub connected framework.
Hub route table: You can create a virtual hub route and apply the route to the virtual hub route table. You can apply multiple routes to the virtual hub route table.
Additional Virtual WAN resources
- Site: This resource is used for site-to-site connections only. The site resource is vpnsite. It represents your on-premises VPN device and its settings. By working with a Virtual WAN partner, you have a built-in solution to automatically export this information to Azure.
Types of connectivity
Virtual WAN allows the following types of connectivity: Site-to-Site VPN, User VPN (Point-to-Site), and ExpressRoute.
Site-to-site VPN connections
You can connect to your resources in Azure over a Site-to-site IPsec/IKE (IKEv2) connection. For more information, see Create a site-to-site connection using Virtual WAN.
This type of connection requires a VPN device or a Virtual WAN Partner device. Virtual WAN partners provide automation for connectivity, which is the ability to export the device info into Azure, download the Azure configuration, and establish connectivity to the Azure Virtual WAN hub. For a list of the available partners and locations, see the Virtual WAN partners and locations article. If your VPN/SD-WAN device provider is not listed in the mentioned link, then you can simplify use the step-by-step instruction Create a site-to-site connection using Virtual WAN to set up the connection.
User VPN (point-to-site) connections
You can connect to your resources in Azure over an IPsec/IKE (IKEv2) or OpenVPN connection. This type of connection requires a VPN client to be configured on the client computer. For more information, see Create a point-to-site connection.
ExpressRoute lets you connect on-premises network to Azure over a private connection. To create the connection, see Create an ExpressRoute connection using Virtual WAN.
You can connect an Azure virtual network to a virtual hub. For more information, see Connect your VNet to a hub.
Transit connectivity between VNets
Virtual WAN allows transit connectivity between VNets. VNets connect to a virtual hub via a virtual network connection. Transit connectivity between the VNets in Standard Virtual WAN is enabled due to the presence of a router in every virtual hub. This router is instantiated when the virtual hub is first created.
The router can have four routing statuses: Provisioned, Provisioning, Failed, or None. The Routing status is located in the Azure portal by navigating to the Virtual Hub page.
- A None status indicates that the Virtual hub did not provision the router. This can happen if the Virtual WAN is of type Basic, or if the virtual hub was deployed prior to the service being made available.
- A Failed status indicates failure during instantiation. In order to instantiate or reset the router, you can locate the Reset Router option by navigating to the virtual hub Overview page in the Azure portal.
Every virtual hub router supports an aggregate throughput up to 50 Gbps. Connectivity between the virtual network connections assumes a total of 2000 VM workload across all VNets in a virtual WAN.
Transit connectivity between VPN and ExpressRoute
Virtual WAN allows transit connectivity between VPN and ExpressRoute. This implies that VPN-connected sites or remote users can communicate with ExpressRoute-connected sites. There is also an implicit assumption that the Branch-to-branch flag is enabled. This flag can be located in the Azure Virtual WAN settings in the Azure portal. All route management is provided by the virtual hub router, which also enables transit connectivity between virtual networks.
Virtual WAN provides advanced routing enhancements. Ability to set up custom route tables, optimize virtual network routing with route association and propagation, logically group route tables with labels and simplify numerous network virtual appliance or shared services routing scenarios.
Global VNet peering
Global VNet Peering provides a mechanism to connect two VNets in different regions. In Virtual WAN, virtual network connections connect VNets to virtual hubs. The user does not need to set up global VNet peering explicitly. VNets connected to virtual hub is same region incur VNet peering charges. VNets connected to virtual hub in a different region incur Global VNet peering charges.
ExpressRoute traffic encryption
Azure Virtual WAN provides ability to encrypt your ExpressRoute traffic. The technique provides an encrypted transit between the on-premises networks and Azure virtual networks over ExpressRoute, without going over the public internet or using public IP addresses. For more information, see IPsec over ExpressRoute for Virtual WAN.
For location information, see the Virtual WAN partners and locations article.
Route tables in Basic and Standard virtual WANs
Route tables now have features for association and propagation. A pre-existing route table is a route table that does not have these features. If you have pre-existing routes in Hub Routing and would like to use the new capabilities, consider the following:
Standard Virtual WAN Customers with pre-existing routes in virtual hub: To use new route table capabilities, please wait until week of August 3rd for the roll out in Azure to complete. If you have pre-existing routes in Routing section for the hub in Azure portal, you will need to first delete them and then attempt creating new route tables (available in the Route Tables section for the hub in Azure portal).
Basic Virtual WAN Customers with pre-existing routes in virtual hub: To use the new route table capabilities, please wait until week of August 3rd for the roll out in Azure to complete. If you have pre-existing routes in Routing section for the hub in Azure portal, you will need to first delete them, then upgrade your Basic Virtual WAN to Standard Virtual WAN. See Upgrade a virtual WAN from Basic to Standard.
Does the user need to have hub and spoke with SD-WAN/VPN devices to use Azure Virtual WAN?
Virtual WAN provides many functionalities built into a single pane of glass such as Site/Site-to-site VPN connectivity, User/P2S connectivity, ExpressRoute connectivity, Virtual Network connectivity, VPN ExpressRoute Interconnectivity, VNet-to-VNet transitive connectivity, Centralized Routing, Azure Firewall and Firewall Manager security, Monitoring, ExpressRoute Encryption, and many other capabilities. You do not have to have all of these use-cases to start using Virtual WAN. You can get started with just one use case. The Virtual WAN architecture is a hub and spoke architecture with scale and performance built in where branches (VPN/SD-WAN devices), users (Azure VPN Clients, openVPN, or IKEv2 Clients), ExpressRoute circuits, Virtual Networks serve as spokes to Virtual Hub(s). All hubs are connected in full mesh in a Standard Virtual WAN making it easy for the user to use the Microsoft backbone for any-to-any (any spoke) connectivity. For hub and spoke with SD-WAN/VPN devices, users can either manually set it up in the Azure Virtual WAN portal or use the Virtual WAN Partner CPE (SD-WAN/VPN) to set up connectivity to Azure. Virtual WAN partners provide automation for connectivity, which is the ability to export the device info into Azure, download the Azure configuration and establish connectivity to the Azure Virtual WAN hub. For Point-to-site/User VPN connectivity, we support Azure VPN client, OpenVPN, or IKEv2 client.
Can you disable fully meshed hubs in a Virtual WAN?
Virtual WAN comes in two flavors: Basic and Standard. In Basic Virtual WAN, hubs are not meshed. In a Standard Virtual WAN, hubs are meshed and automatically connected when the virtual WAN is first set up. The user does not need to do anything specific. The user also does not have to disable or enable the functionality to obtain meshed hubs. Virtual WAN provides you many routing options to steer traffic between any spoke (VNet, VPN, or ExpressRoute). It provides the ease of fully meshed hubs, and also the flexibility of routing traffic per your needs.
How are Availability Zones and resiliency handled in Virtual WAN?
Virtual WAN is a collection of hubs and services made available inside the hub. The user can have as many virtual wan per their needs. In a Virtual WAN hub, there are multiple services like VPN, ExpressRoute etc. Each of these services is deployed in an Availability Zones region, if the region supports Availability Zones. If a region becomes an Availability Zone after the initial deployment in the hub, the user can recreate the gateways, which will trigger an Availability Zone deployment. All gateways are provisioned in a hub as active-active, implying there is resiliency built in within a hub. Users can connect to multiple hubs if they want resiliency across regions. While the concept of Virtual WAN is global, the actual Virtual WAN resource is Resource Manager-based and deployed regionally. If the virtual WAN region itself were to have an issue, all hubs in that virtual WAN will continue to function as is, but the user will not be able to create new hubs until the virtual WAN region is available.
What client does the Azure Virtual WAN User VPN (Point-to-site) support?
Virtual WAN supports Azure VPN client, OpenVPN Client, or any IKEv2 client. Azure AD authentication is supported with Azure VPN Client.A minimum of Windows 10 client OS version 17763.0 or higher is required. OpenVPN client(s) can support certificate-based authentication. Once cert-based auth is selected on the gateway, you will see the .ovpn file to download to your device. IKEv2 supports both certificate and RADIUS authentication.
For User VPN (Point-to-site)- Why is the P2S client pool split into two routes?
Each gateway has two instances, the split happens so that each gateway instance can independently allocate client IPs for connected clients and traffic from the virtual network is routed back to the correct gateway instance to avoid inter-gateway instance hop.
How do I add DNS servers for P2S clients?
There are two options to add DNS servers for the P2S clients. The first method is preferred as it adds the custom DNS servers to the gateway instead of the client.
Use the following PowerShell script to add the custom DNS servers. Replace the values for your environment.
// Define variables $rgName = "testRG1" $virtualHubName = "virtualHub1" $P2SvpnGatewayName = "testP2SVpnGateway1" $vpnClientAddressSpaces = $vpnServerConfiguration1Name = "vpnServerConfig1" $vpnClientAddressSpaces = New-Object string 2 $vpnClientAddressSpaces = "192.168.2.0/24" $vpnClientAddressSpaces = "192.168.3.0/24" $customDnsServers = New-Object string 2 $customDnsServers = "184.108.40.206" $customDnsServers = "220.127.116.11" $virtualHub = $virtualHub = Get-AzVirtualHub -ResourceGroupName $rgName -Name $virtualHubName $vpnServerConfig1 = Get-AzVpnServerConfiguration -ResourceGroupName $rgName -Name $vpnServerConfiguration1Name // Specify custom dns servers for P2SVpnGateway VirtualHub while creating gateway createdP2SVpnGateway = New-AzP2sVpnGateway -ResourceGroupName $rgname -Name $P2SvpnGatewayName -VirtualHub $virtualHub -VpnGatewayScaleUnit 1 -VpnClientAddressPool $vpnClientAddressSpaces -VpnServerConfiguration $vpnServerConfig1 -CustomDnsServer $customDnsServers // Specify custom dns servers for P2SVpnGateway VirtualHub while updating existing gateway $P2SVpnGateway = Get-AzP2sVpnGateway -ResourceGroupName $rgName -Name $P2SvpnGatewayName $updatedP2SVpnGateway = Update-AzP2sVpnGateway -ResourceGroupName $rgName -Name $P2SvpnGatewayName -CustomDnsServer $customDnsServers // Re-generate Vpn profile either from PS/Portal for Vpn clients to have the specified dns servers
Or, if you are using the Azure VPN Client for Windows 10, you can modify the downloaded profile XML file and add the <dnsservers><dnsserver> </dnsserver></dnsservers> tags before importing it.
<azvpnprofile> <clientconfig> <dnsservers> <dnsserver>x.x.x.x</dnsserver> <dnsserver>y.y.y.y</dnsserver> </dnsservers> </clientconfig> </azvpnprofile>
For User VPN (Point-to-site)- how many clients are supported?
Each User VPN P2S gateway has two instances and each instance supports upto certain users as the scale unit changes. Scale unit 1-3 supports 500 connections, Scale unit 4-6 supports 1000 connections, Scale unit 7-12 supports 5000 connections and Scale unit 13-20 supports up to 10,000 connections.
As an example, lets say the user chooses 1 scale unit. Each scale unit would imply an active-active gateway deployed and each of the instances (in this case 2) would support up to 500 connections. Since you can get 500 connections * 2 per gateway, it does not mean that you plan for 1000 instead of the 500 for this scale unit. Instances may need to be serviced during which connectivity for the extra 500 may be interrupted if you surpass the recommended connection count. Also, be sure to plan for downtime in case you decide to scale up or down on the scale unit, or change the point-to-site configuration on the VPN gateway.
What is the difference between an Azure virtual network gateway (VPN Gateway) and an Azure Virtual WAN VPN gateway?
Virtual WAN provides large-scale site-to-site connectivity and is built for throughput, scalability, and ease of use. When you connect a site to a Virtual WAN VPN gateway, it is different from a regular virtual network gateway that uses a gateway type 'VPN'. Similarly, when you connect an ExpressRoute circuit to a Virtual WAN hub, it uses a different resource for the ExpressRoute gateway than the regular virtual network gateway that uses gateway type 'ExpressRoute'.
Virtual WAN supports up to 20 Gbps aggregate throughput both for VPN and ExpressRoute. Virtual WAN also has automation for connectivity with an ecosystem of CPE branch device partners. CPE branch devices have built-in automation that autoprovisions and connects into Azure Virtual WAN. These devices are available from a growing ecosystem of SD-WAN and VPN partners. See the Preferred Partner List.
How is Virtual WAN different from an Azure virtual network gateway?
A virtual network gateway VPN is limited to 30 tunnels. For connections, you should use Virtual WAN for large-scale VPN. You can connect up to 1,000 branch connections per region (virtual hub) with aggregate of 20 Gbps per hub. A connection is an active-active tunnel from the on-premises VPN device to the virtual hub. You can have one hub per region, which means you can connect more than 1,000 branches across hubs.
What is a Virtual WAN Gateway Scale Unit
A scale unit is a unit defined to pick an aggregate throughput of a gateway in Virtual hub. 1 scale unit of VPN = 500 Mbps. 1 scale unit of ExpressRoute = 2 Gbps. Example: 10 scale unit of VPN would imply 500 Mbps * 10 = 5 Gbps
Which device providers (Virtual WAN partners) are supported?
At this time, many partners support the fully automated Virtual WAN experience. For more information, see Virtual WAN partners.
What are the Virtual WAN partner automation steps?
For partner automation steps, see Virtual WAN partner automation.
Am I required to use a preferred partner device?
No. You can use any VPN-capable device that adheres to the Azure requirements for IKEv2/IKEv1 IPsec support. Virtual WAN also has CPE partner solutions that automate connectivity to Azure Virtual WAN making it easier to set up IPsec VPN connections at scale.
How do Virtual WAN partners automate connectivity with Azure Virtual WAN?
Software-defined connectivity solutions typically manage their branch devices using a controller, or a device provisioning center. The controller can use Azure APIs to automate connectivity to the Azure Virtual WAN. The automation includes uploading branch information, downloading the Azure configuration, setting up IPSec tunnels into Azure Virtual hubs, and automatically setting up connectivity form the branch device to Azure Virtual WAN. When you have hundreds of branches, connecting using Virtual WAN CPE Partners is easy because the onboarding experience takes away the need to set up, configure, and manage large-scale IPsec connectivity. For more information, see Virtual WAN partner automation.
What if a device I am using is not in the Virtual WAN partner list? Can I still use it to connect to Azure Virtual WAN VPN?
Yes as long as the device supports IPsec IKEv1 or IKEv2. Virtual WAN partners automate connectivity from the device to Azure VPN end points. This implies automating steps such as 'branch information upload', 'IPsec and configuration' and 'connectivity'.Since your device is not from a Virtual WAN partner ecosystem, you will need to do the heavy lifting of manually taking the Azure configuration and updating your device to set up IPsec connectivity.
How do new partners that are not listed in your launch partner list get onboarded?
All virtual WAN APIs are open API. You can go over the documentation Virtual WAN partner automation to assess technical feasibility. An ideal partner is one that has a device that can be provisioned for IKEv1 or IKEv2 IPsec connectivity. Once the company has completed the automation work for their CPE device based on the automation guidelines provided above, you can reach out to firstname.lastname@example.org to be listed here Connectivity through partners. If you are a customer that would like a certain company solution to be listed as a Virtual WAN partner, please have the company contact the Virtual WAN by sending an email to email@example.com.
How is Virtual WAN supporting SD-WAN devices?
Virtual WAN partners automate IPsec connectivity to Azure VPN end points. If the Virtual WAN partner is an SD-WAN provider, then it is implied that the SD-WAN controller manages automation and IPsec connectivity to Azure VPN end points. If the SD-WAN device requires its own end point instead of Azure VPN for any proprietary SD-WAN functionality, you can deploy the SD-WAN end point in an Azure VNet and coexist with Azure Virtual WAN.
How many VPN devices can connect to a single hub?
Up to 1,000 connections are supported per virtual hub. Each connection consists of four links and each link connection supports two tunnels that are in an active-active configuration. The tunnels terminate in an Azure virtual hub VPN gateway. Links represent the physical ISP link at the branch/VPN device.
What is a branch connection to Azure Virtual WAN?
A connection from a branch or VPN device into Azure Virtual WAN is nothing but a VPN connection that connects virtually the VPN Site and the Azure VPN Gateway in a virtual hub.
Can the on-premises VPN device connect to multiple Hubs?
Yes. Traffic flow, when commencing, is from the on-premises device to the closest Microsoft network edge, and then to the virtual hub.
Are there new Resource Manager resources available for Virtual WAN?
Yes, Virtual WAN has new Resource Manager resources. For more information, please see the Overview.
Can I deploy and use my favorite network virtual appliance (in an NVA VNet) with Azure Virtual WAN?
Yes, you can connect your favorite network virtual appliance (NVA) VNet to the Azure Virtual WAN.
Can I create a Network Virtual Appliance inside the virtual hub?
A Network Virtual Appliance (NVA) cannot be deployed inside a virtual hub. However, you can create it in a spoke VNet that is connected to the virtual hub and enable appropriate routing to direct traffic per your needs.
Can a spoke VNet have a virtual network gateway?
No. The spoke VNet cannot have a virtual network gateway if it is connected to the virtual hub.
Is there support for BGP in VPN connectivity?
Yes, BGP is supported. When you create a VPN site, you can provide the BGP parameters in it. This will imply that any connections created in Azure for that site will be enabled for BGP.
Is there any licensing or pricing information for Virtual WAN?
Yes. See the Pricing page.
Is it possible to construct Azure Virtual WAN with a Resource Manager template?
A simple configuration of one Virtual WAN with one hub and one vpnsite can be created using an quickstart template. Virtual WAN is primarily a REST or portal driven service.
Can spoke VNets connected to a virtual hub communicate with each other (V2V Transit)?
Yes. Standard Virtual WAN supports VNet-to-VNet transitive connectivity via the Virtual WAN hub that the VNets are connected to. In Virtual WAN terminology, we refer to these paths as “local Virtual WAN VNet transit” for VNets connected to a Virtual Wan Hub within a single region, and “global Virtual WAN VNet transit” for VNets connected through multiple Virtual WAN Hubs across two or more regions. For some scenarios, spoke VNets can also be directly peered with each other using Virtual Network Peering in addition to local or global Virtual WAN VNet transit. In this case, VNet Peering takes precedence over the transitive connection via the Virtual WAN hub.
Is branch-to-branch connectivity allowed in Virtual WAN?
Yes, branch-to-branch connectivity is available in Virtual WAN. Branch is conceptually applicable to VPN Site, ExpressRoute circuits, or Point-to-Site/User VPN users. Enabling branch to branch is enabled by default and can be located in WAN Configuration settings. This enables VPN branches/users to connect to other VPN branches as well as transit connectivity is enabled between VPN and ExpressRoute users.
Does branch-to-branch traffic traverse through the Azure Virtual WAN?
Does Virtual WAN require ExpressRoute from each site?
No. Virtual WAN does not require ExpressRoute from each site. Your sites may be connected to a provider network using an ExpressRoute circuit. For Sites that are connected using ExpressRoute to a virtual hub as well as IPsec VPN into the same hub, virtual hub provides transit connectivity between the VPN and ExpressRoute user.
Is there a network throughput or connection limit when using Azure Virtual WAN?
Network throughput is per service in a virtual WAN hub. While you can have as many virtual WANs as you like, each Virtual WAN allows 1 hub per region. In each hub, the VPN Aggregate throughput is up to 20 Gbps, the ExpressRoute aggregate throughput is up to 20 Gbps and the User VPN/Point-to-site VPN aggregate throughput is up to 20 Gbps. The router in virtual hub supports up to 50 Gbps for VNet-to-VNet traffic flows and assumes a total of 2000 VM workload across all VNets in Virtual WAN hubs.
When VPN Sites connect into a hub, they do so with connections. Virtual WAN supports up to 1000 connections or 2000 IPsec tunnels per virtual hub. When remote users connect into virtual hub, they connect to the P2S VPN gateway, which supports up to 10,000 users depending on the scale unit(bandwidth) chosen for the P2S VPN gateway in the virtual hub.
What is the total VPN throughput of a VPN tunnel and a connection?
The total VPN throughput of a hub is up to 20 Gbps based on the chosen scale unit of the VPN gateway. Throughput is shared by all existing connections. Each tunnel in a connection can support up to 1 Gbps.
I don't see the 20 Gbps setting for the virtual hub in portal. How do I configure that?
Navigate to the VPN gateway inside a hub on the portal and click on the scale unit to change it to the appropriate setting.
Does Virtual WAN allow the on-premises device to utilize multiple ISPs in parallel, or is it always a single VPN tunnel?
On-premises device solutions can apply traffic policies to steer traffic across multiple tunnels into the Azure Virtual WAN hub (VPN gateway in the virtual hub).
What is global transit architecture?
For information about global transit architecture, see Global transit network architecture and Virtual WAN.
How is traffic routed on the Azure backbone?
The traffic follows the pattern: branch device ->ISP->Microsoft network edge->Microsoft DC (hub VNet)->Microsoft network edge->ISP->branch device
In this model, what do you need at each site? Just an internet connection?
Yes. An internet connection and physical device that supports IPsec, preferably from our integrated Virtual WAN partners. Optionally, you can manually manage the configuration and connectivity to Azure from your preferred device.
How do I enable default route (0.0.0.0/0) in a connection (VPN, ExpressRoute, or Virtual Network):
A virtual hub can propagate a learned default route to a virtual network/site-to-site VPN/ExpressRoute connection if the flag is 'Enabled' on the connection. This flag is visible when the user edits a virtual network connection, a VPN connection, or an ExpressRoute connection. By default, this flag is disabled when a site or an ExpressRoute circuit is connected to a hub. It is enabled by default when a virtual network connection is added to connect a VNet to a virtual hub. The default route does not originate in the Virtual WAN hub; the default route is propagated if it is already learned by the Virtual WAN hub as a result of deploying a firewall in the hub, or if another connected site has forced-tunneling enabled.
How does the virtual hub in a Virtual WAN select the best path for a route from multiple hubs
If a Virtual Hub learns the same route from multiple remote hubs, the order in which it decides is as follows:
- Longest prefix match.
- Local routes over interhub.
- Static routes over BGP: This is in context to the decision being made by Virtual Hub router. However if the decision maker is the VPN gateway where a site advertises routes via BGP or provides static address prefixes, static routes may be preferred over BGP routes.
- ExpressRoute (ER) over VPN: ER is preferred over VPN when the context is a local hub. Transit connectivity between ExpressRoute circuits is only available through Global Reach. Therefore in scenarios where ExpressRoute circuit is connected to one hub and there is another ExpressRoute circuit connected to a different hub with VPN connection, VPN may be preferred for inter-hub scenarios.
- AS path length.
Does Virtual WAN hub allow connectivity between ExpressRoute circuits.
Transit between ER-to-ER is always via Global reach. Virtual hub gateways are deployed in DC or Azure regions. When two ExpressRoute circuits connect via Global reach, there is no need for the traffic to come all the way from the edge routers to the virtual hub DC.
Is there a concept of weight in Azure Virtual WAN circuits or VPN connections
When multiple ExpressRoute circuits are connected to a virtual hub, routing weight on the connection provides a mechanism for the ExpressRoute in the virtual hub to prefer one circuit over the other. There is no mechanism to set a weight on a VPN connection. Azure always prefers an ExpressRoute connection over a VPN connection within a single hub.
When two hubs (hub 1 and 2) are connected and there is an ExpressRoute circuit connected as a bow-tie to both the hubs, what is the path for a VNet connected to hub 1 to reach a VNet connected in hub 2?
Current behavior is to prefer the ExpressRoute circuit path over hub-to-hub for VNet-to-VNet connectivity. However, this is not encouraged in a virtual WAN setup. Virtual WAN team is working on a fix to enable the preference for hub-to-hub over the ExpressRoute path. The recommendation is for multiple ExpressRoute circuits (different providers) to connect to one hub and use the hub-to-hub connectivity provided by Virtual WAN for inter-region traffic flows.
Is there support for IPv6 in Virtual WAN?
IPv6 is not supported in Virtual WAN hub and its gateways. If you have a VNet that has IPv6 support and you would like to connect the VNet to Virtual WAN, this scenario not currently supported.