How to advertise VNET IPv6 prefixes via Expressroute to on prem BGP peer

Question

I have VNET on dual stack. I have multiple IPv6 and IPv4 subnets. On Expressroute I have configured private IPv6 BGP peering with on prem router. Connection between VNET and Expressroute is Virtual Network Gateway in dual stack. I also have VM in VNET which is in dual stack with 3 interfaces and all are active. When I click on Expressroute private peering route table I can only see IPv4 /16 prefix of my VNET. How can I get IPv6 prefixes being advertised between VNET and onprem network?

I found few articles in Azure KB however issue is still present.

Appreciate all the help in advance!

Answer 1

Hello @Alex ,

Welcome to Microsoft Q&A Platform. Thank you for reaching out & hope you are doing well.

I understand that you would like to advertise VNET IPv6 prefixes via ExpressRoute to on prem BGP peer.

Could you please confirm if your existing gateway is zone-redundant?

To use IPv6-based private peering over ExpressRoute, you need to create a gateway with AZ SKU (ErGw1AZ, ErGw2AZ, ErGw3AZ) for -GatewaySku or use Non-AZ SKU (Standard, HighPerformance, UltraPerformance) for -GatewaySKU with Standard and Static Public IP.

Refer: https://learn.microsoft.com/en-us/azure/expressroute/expressroute-howto-add-gateway-resource-manager#add-a-gateway

If you have an existing gateway that is not zone-redundant (meaning it is Standard, High Performance, or Ultra Performance SKU) and uses a Basic public IP address, you will need to delete and recreate the gateway using any SKU and a Standard, Static public IP address or use AZ SKU.

Refer: https://learn.microsoft.com/en-us/azure/expressroute/expressroute-howto-add-ipv6-portal

As mentioned in the IPv6 support for private peering limitations,

While IPv6 support is available for connections to deployments in global Azure regions, it doesn't support the following use case: Connections to existing ExpressRoute gateways that aren't zone-redundant. Newly created ExpressRoute gateways of any SKU (both zone-redundant and not) using a Standard, Static IP address can be used for dual-stack ExpressRoute connections.

Also, as noted in the above public documentation,

Some aspects of the portal experience are still being implemented. Therefore, follow the exact order of steps provided in the document to successfully add IPv6 support via the portal. Specifically, make sure to create your virtual network and subnet, or add IPv6 address space to your existing virtual network and GatewaySubnet, prior to creating a new virtual network gateway in the portal.

So, I would request you to validate the above and if needed, delete and recreate the ExpressRoute gateway using the required SKU and IP address (specifically if you are using Azure Portal to make the changes). And you must also configure IPv6 on your on-premises CPE device.

Kindly let us know if the above helps or you need further assistance on this issue.

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