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Routing weight on Azure connection between multiple VNETs and a single Express Route circuit

Alex H 145 Reputation points
2025-10-07T07:33:51.77+00:00

Hi,

I have a question about Route Weight on Connection between VNETs and an ER circuit.

Document mentions Routing weight is used to determine the primary and secondary connections. The connection with the higher routing weight is the preferred circuit.

However, I would like to confirm whether this behavior applies when a single ExpressRoute circuit has connections to multiple VNETs.

For example:

  • An ExpressRoute circuit has two connections - one to VNET1 with a routing weight of 50, and one to VNET2 with a routing weight of 0.
  • Both VNET1 and VNET2 advertise 0.0.0.0/0 to the ExpressRoute circuit, along with their respective VNET-specific routes.

In this scenario, my understanding is that the ExpressRoute circuit would learn 0.0.0.0/0 from both VNETs but would prefer the path through VNET1 due to its higher routing weight.

As a result, internet-bound traffic from on-premises to Azure would always be routed via the VNET1 gateway, as long as that path remains available.

Could you please confirm if this assumption is correct?

Thanks

Alex

Azure ExpressRoute
Azure ExpressRoute
An Azure service that provides private connections between Azure datacenters and infrastructure, either on premises or in a colocation environment.
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  1. Ravi Varma Mudduluru 4,090 Reputation points Microsoft External Staff Moderator
    2025-10-07T07:46:44.13+00:00

    Hello @Alex H

    Thanks for reaching out to Microsoft Q&A. 

    I understand that you need clarity on how routing weight works for ExpressRoute connections to multiple VNETs.

    In this scenario, the ExpressRoute circuit will prioritize the path through VNET1, as its routing weight of 50 is higher than VNET2's weight of 0.

    Yes, your assumption is correct. With both VNETs advertising 0.0.0.0/0, the ExpressRoute circuit receives routes from each one. However, the routing weight determines that traffic will use VNET1 as long as that route is available. As a result, internet-bound traffic from your on-premises network to Azure will go through the gateway connected to VNET1.

    • The higher the routing weight, the more preferred the route.
    • Since both VNETs advertise the same routes, the path with the higher weight (VNET1) will be chosen for routing.

    If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".

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