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Azure Virtual WAN - ExpressRoute Gateway traffic flow

Peter Stieber 180 Reputation points
2025-07-25T18:14:49.6+00:00

Hello,

I'm trying to better understand the traffic flow in an Azure Virtual WAN (vWAN) setup that includes ExpressRoute.

When inspecting the ExpressRoute route table, I notice a BGP peer IP that falls within the Virtual Hub address space—for example, something like 10.254.x.x. I'm trying to determine the nature of this IP.

Is this IP specifically associated with the ExpressRoute gateway, or is it a general address used by the Virtual Hub? It doesn’t match any of the Virtual Hub’s virtualRouterIps.

Does traffic from the ExpressRoute circuit actually flow through the ExpressRoute gateway?

Azure Virtual WAN
Azure Virtual WAN
An Azure virtual networking service that provides optimized and automated branch-to-branch connectivity.
Accepted answer
  1. Praveen Bandaru 6,850 Reputation points Microsoft External Staff Moderator
    2025-07-28T03:31:00.2+00:00

    Hello Peter Stieber
    I understand that you’re looking for clarification on the traffic flow in your Azure Virtual WAN setup with ExpressRoute, especially concerning a BGP peer IP listed in your route table.

    The BGP peer IP address located within the Virtual Hub address space (such as 10.254.x.x) is generally linked to the ExpressRoute gateway. 

    This address is used for BGP peering between your on-premises network and the Azure Virtual Hub. While it might not match the virtualRouterIps, it is still an essential part of the routing setup for ExpressRoute connections in the Virtual WAN environment.

    Also, please check in the VHUB overview in the Azure portal. In the JSON file, you can find the Azure Route Server private IPs. You can validate these as well to confirm if it is Route Server IP or not. If that IP is not a route server IP, then it is definitely a BGP peer IP only.

    Yes, traffic from the ExpressRoute circuit does pass through the ExpressRoute gateway when connecting on-premises networks to Azure resources. The gateway serves as the entry point, allowing your on-premises traffic to reach Azure Virtual Network resources via the designated Virtual Hub.

    Check the reference document:

    https://docs.azure.cn/en-us/expressroute/expressroute-routing#support-for-bgp-communities

    Hope the above answer helps! Please let us know do you have any further queries.

    Please do not forget to “up-vote” wherever the information provided helps you, this can be beneficial to other community members.

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