Getting "Multiple address prefixes not supported for GatewaySubnet" when provisioning a VirtualNetworkGateway

Wimatwork 1 Reputation point
2021-11-02T23:29:56.423+00:00

I'm configuring a dualstack Virtual Network Gateway for an expressroute setup. (the expressroute peering is already setup and works fine over ipv4/ipv6)

First a created a dual stack Virtual Network, containing an ipv4 /24 and /19 and an ipv6 /48 and /64 range
I've created a "Gateway Subnet" in it, following the instructions, used a /24 for the "subnet address range" and a /64 for the ipv6 range

145760-image.png

Then I try to create the virtual network gateway, using the virtual network containing the GatewaySubnet I created above.

145914-image.png

And it now fails with the MultipleAddressPrefixesNotSupportedForGateWaySubnet message 

   {"code":"DeploymentFailed","message":"At least one resource deployment operation failed. Please list deployment operations for details. Please see https://aka.ms/DeployOperations for usage details.","details":[{"code":"MultipleAddressPrefixesNotSupportedForGateWaySubnet","message":"Multiple address prefixes not supported for GatewaySubnet /subscriptions/9d8df981-xxxx-yyyy-zzzz-17c72dcf9bba/resourceGroups/ExpressRoutePOC-rg/providers/Microsoft.Network/virtualNetworks/ExpressRoutePOC-Prod/subnets/GatewaySubnet."}]}

I can't find any references to this error on google, anyone an idea what and if I'm doing something wrong?

Thanks

Azure VPN Gateway
Azure VPN Gateway
An Azure service that enables the connection of on-premises networks to Azure through site-to-site virtual private networks.
1,379 questions
Azure ExpressRoute
Azure ExpressRoute
An Azure service that provides private connections between Azure datacenters and infrastructure, either on premises or in a colocation environment.
322 questions
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  1. msrini-MSFT 9,256 Reputation points Microsoft Employee
    2021-11-03T04:57:25.107+00:00

    Hi @Wimatwork ,

    Can you delete the Gateway Subnet and recreate it with IPv4 address only and try again ?

    Is there any use case for you to have both IPv4 and IPv6 address space for Gateway Subnet ?

    If you still need both stack, then I need to take a deeper look as why this happened for which I need your Subscription ID and the time when you made this call. You can send that info to msrini@microsoft.com.

    Let me know if the above suggestion works.

    Regards,
    Msrini

  2. msrini-MSFT 9,256 Reputation points Microsoft Employee
    2021-11-03T12:10:52.603+00:00

    @Wimatwork ,

    I see that you have 2 IPv6 address space which caused this issue.

    1. Delete the gateway subnet.
    2. Delete the /64 address space that you created for the Gateway Subnet.
    3. Create a new subnet with the existing IPv6 address space
    4. Create Gateway.

    Regards,
    Karthik Srinivas