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About migrating to an availability zone-enabled ExpressRoute virtual network gateway

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When you create an ExpressRoute virtual network gateway, you need to choose the gateway SKU. If you choose a higher-level SKU, more CPUs and network bandwidth are allocated to the gateway. As a result, the gateway can support higher network throughput and more dependable network connections to the virtual network.

The following SKUs are available for ExpressRoute virtual network gateways:

  • Standard
  • HighPerformance
  • UltraPerformance
  • ErGw1Az
  • ErGw2Az
  • ErGw3Az
  • ErGwScale (Preview)

Availability zone enabled SKUs

The ErGw1Az, ErGw2Az, ErGw3Az, and ErGwScale (Preview) SKUs, also known as Az-Enabled SKUs, support Availability zone deployments. This feature provides high availability and resiliency to the gateway by distributing the gateway across multiple availability zones.

The Standard, HighPerformance, and UltraPerformance SKUs, which are also known as nonavailability zone enabled SKUs are historically associated with Basic IPs, don't support the distribution of the gateway across multiple availability zones.

For enhanced reliability, it's recommended to use an Availability-Zone Enabled virtual network gateway SKU. These SKUs support a zone-redundant setup and are, by default, associated with Standard IPs. This setup ensures that even if one zone experiences an issue, the virtual network gateway infrastructure remains operational due to the distribution across multiple zones. For a deeper understanding of zone redundant gateways, please refer to Availability Zone deployments.

Gateway migration experience

Historically, users had to use the Resize-AzVirtualNetworkGateway PowerShell command or delete and recreate the virtual network gateway to migrate between SKUs.

With the guided gateway migration experience you can deploy a second virtual network gateway in the same GatewaySubnet and Azure automatically transfers the control plane and data path configuration from the old gateway to the new one. During the migration process, there will be two virtual network gateways in operation within the same GatewaySubnet. This feature is designed to support migrations without downtime. However, users may experience brief connectivity issues or interruptions during the migration process.

Gateway migration is recommended if you have a non-Az enabled Gateway SKU or a non-Az enabled Gateway Basic IP Gateway SKU.

Migrate from Non-Az enabled Gateway SKU Migrate to Az-enabled Gateway SKU
Standard, HighPerformance, UltraPerformance ErGw1Az, ErGw2Az, ErGw3Az, ErGwScale (Preview)
Basic IP Standard IP

Supported migration scenarios

Azure portal

The guided gateway migration experience supports non-Az-enabled SKU to Az-enabled SKU migration. To learn more, see Migrate to an availability zone-enabled ExpressRoute virtual network gateway in Azure portal.

Azure PowerShell

The guided gateway migration experience supports:

  • Non-Az-enabled SKU on Basic IP to Non-az enabled SKU on Standard IP.
  • Non-Az-enabled SKU to Az-enabled SKU.

It's recommended to migrate to an Az-enabled SKU for enhanced reliability and high availability. To learn more, see Migrate to an availability zone-enabled ExpressRoute virtual network gateway using PowerShell.

Limitations

The guided gateway migration experience doesn't support these scenarios:

  • Downgrade scenarios, Az-enabled Gateway SKU to non-Az-enabled Gateway SKU.

Private endpoints (PEs) in the virtual network, connected over ExpressRoute private peering, might have connectivity problems during the migration. To understand and reduce this issue, see Private endpoint connectivity.

Common validation errors

In the gateway migration experience, you need to validate if your resource is capable of migration. Here are some Common migration errors:

Virtual network

  • Gateway Subnet needs two or more prefixes for migration.
  • MaxGatewayCountInVnetReached – Reached maximum number of gateways that can be created in a Virtual Network.

If your first address prefix is large enough for the second gateway creation and deployment, such as /24, you won't need to add a second prefix.

Connection

The virtual network gateway connection resource isn't in a succeed state.

Next steps