Azure Virtual WAN is a networking service that brings together networking, security, and routing functionalities into a single, unified platform.
Let’s say you’ve got a few branch offices, each with its own on-premises network, and you want to connect them all securely and efficiently to your Azure resources. Instead of setting up individual VPN tunnels from each branch to your Azure Virtual Network (VNet), Virtual WAN acts as a central hub. Think of it like a massive, managed router in the cloud.
Here’s a simplified view of how it works in action. Imagine you have two branch offices, "London" and "New York," and an Azure VNet with some virtual machines (VMs) in it.
First, you deploy a Virtual WAN resource in Azure. Then, you create a Virtual Hub within that Virtual WAN. This Virtual Hub is the core of your connectivity.
Next, you set up Virtual Network (VNet) connections. You connect your Azure VNet (where your VMs live) to the Virtual Hub. This makes your Azure resources accessible through the hub.
For your branch offices, you deploy Virtual WAN VPN sites. You configure an on-premises VPN device in London to establish a Site-to-Site VPN connection to the Virtual Hub. The same is done for New York. These aren’t direct tunnels to your Azure VNet; they terminate at the Virtual Hub.
Now, when a VM in Azure needs to talk to a server in London, the traffic goes from the Azure VNet to the Virtual Hub, and then through the VPN tunnel to London. Similarly, traffic from London to Azure VNet goes through the VPN tunnel to the Virtual Hub, and then to the Azure VNet.
The magic is that the Virtual Hub handles all the routing. It learns about the routes from your Azure VNet and from each of your branch offices. It then propagates these routes so that all connected sites (Azure VNet and branch offices) know how to reach each other. You don’t need to manually configure complex routing tables on individual VPN gateways or VNets.
The Virtual Hub can also integrate with Azure Firewall for centralized security inspection or with a Network Virtual Appliance (NVA) for advanced routing and filtering. This means you can enforce consistent security policies across all your connected sites.
For example, if you wanted to inspect all traffic going from your branch offices to Azure, you would deploy Azure Firewall into the Virtual Hub. Then, you’d configure the Virtual Hub’s routing to send this branch-to-Azure traffic through the firewall before it reaches your Azure VNet.
The exact levers you control are primarily within the Virtual Hub configuration. You manage the VNet connections, the VPN site connections, and crucially, the routing. You can define routing tables within the hub to control how traffic flows between different connections (e.g., which branch office can talk to which Azure VNet, or if traffic should go through a firewall). You also configure the IP address spaces for your branch offices and Azure VNets, ensuring they don’t overlap.
What most people don’t realize is that the Virtual Hub is not just a passive router; it’s an active component that can host services like Azure Firewall or NVAs, and it dynamically exchanges routes with connected spokes (VNets) and branches using BGP. This dynamic route exchange is key to simplifying management at scale.
The next concept you’ll likely encounter is optimizing traffic flow for specific scenarios, such as connecting multiple Azure regions or enabling express route circuits.