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Are you trying to connect your hub to a VPN Gateway manually by setting up BGP peering? If so, here’s an important tip to keep in mind, especially when working with Virtual WAN. The hub already exchanges routing information with the VPN Gateway automatically. Adding an extra BGP connection to the gateway’s BGP IP address can cause overlaps or conflicts because it duplicates what’s already in place.
In a Hub Virtual Network setup, Azure Route Server (ARS) does not require manual BGP peering with Azure VPN Gateway or ExpressRoute Gateway. When you deploy ARS within the same virtual network and activate route exchange, the platform automatically manages the peering with those gateways. Trying to manually add a BGP peer from ARS to your VPN Gateway will likely fail because the connections are already handled behind the scenes by Azure.
The best approach instead is to deploy ARS in its designated subnet, called the RouteServerSubnet (/26), within your Hub VNet. Then, enable route exchange in ARS. Once set up this way, ARS will automatically exchange routes with your VPN Gateway and, if you have one, the ExpressRoute Gateway. This setup allows seamless, transitive routing between your on-premises network, Azure Virtual WAN, and NVAs — making your network communication smoother and more reliable.
Here’s a helpful article that explains more about this setup: Azure Route Server and VPN Support.
To understand how route exchange works: When you deploy Azure Route Server alongside your virtual network gateways and network virtual appliances (NVAs), it allows these components to share routing information dynamically. However, by default, the Route Server does not propagate routes between different network components. Each device, whether it’s a VPN gateway, ExpressRoute, or NVA, only exchanges routes directly with the Route Server.
A crucial point to remember is that attempting to manually set up a BGP peer between ARS and your Azure VPN Gateway by using their BGP ASN or IP addresses generally won’t work. These sessions are managed by Microsoft’s service and are not intended for direct user configuration.
In short, do not try to peer ARS directly with your VPN Gateway. This isn’t supported and can cause issues. ARS is designed for peering with NVAs inside your virtual network. VPN Gateway handles BGP with your on-premises devices over the VPN connection itself. If you need centralized transit routing between different spokes and gateways, consider using Virtual WAN. Otherwise, keep ARS dedicated to NVA scenarios for effective route management.
To wrap up, route propagation in Virtual WAN hubs is automatically managed by the service. You do not need, and should not attempt, to add extra BGP connections to the Azure-managed gateways.
Hope this helps clear things up! If anything is still unclear or you have more questions, feel free to ask in the comments below.
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