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About ExpressRoute Gateway Migration

This article explains the ExpressRoute gateway migration process, enabling you to move from non-Availability Zone (non-Az)-enabled SKUs to Az-enabled SKUs, and from Basic IP to Standard IP. Migrating to Az-enabled SKUs and Standard IPs improves the reliability and high availability of your ExpressRoute virtual network gateways.

For guidance on upgrading Basic SKU public IP addresses for other networking services, see Upgrading Basic to Standard SKU.

Important

On September 30, 2025, Basic SKU public IPs will be retired. For more information, see the official announcement. If you're currently using Basic SKU public IPs, make sure to upgrade to Standard SKU public IPs prior to the retirement date.

Gateway SKUs

The ErGw1Az, ErGw2Az, ErGw3Az, and ErGwScale (Preview) SKUs are known as Availability Zone (Az)-enabled SKUs. These SKUs allow deployment across multiple availability zones, increasing resiliency and high availability by distributing gateway resources across zones.

By comparison, the Standard, HighPerformance, and UltraPerformance SKUs are non-Az-enabled. They're typically used with Basic public IP addresses and don't support availability zone distribution.

Gateway migration experience

The gateway migration experience allows you to deploy a second virtual network gateway in the same GatewaySubnet. Azure migrates your configurations from the old gateway to the new one. Both gateways run simultaneously during migration, minimizing disruption – though brief connectivity interruptions may still occur.

After migration, the old gateway and its connections are deleted, and the new gateway is tagged with CreatedBy: GatewaySKUMigration to identify it as a migrated resource and shouldn’t be deleted.

Supported Migration Scenarios

The guided gateway migration experience supports the following scenarios:

  • Migrating from a non-Az-enabled SKU with a Basic IP to a non-Az-enabled SKU with a Standard IP.
  • Migrating from a non-Az-enabled SKU with a Basic IP to an Az-enabled SKU with a Standard IP.

If you have an ExpressRoute gateway deployed in the same virtual network as a VPN Gateway, you can use the ExpressRoute Gateway migration tool. There is no expected impact to VPN Gateway traffic during this process.

Learn how to migrate using the Azure portal.
Learn how to migrate using PowerShell.

For enhanced reliability and high availability, we recommend migrating to an Az-enabled SKU.

Steps to migrate to a new gateway

  1. Validate: Check that all resources are in a succeeded state. If any prerequisites aren't met, validation fails and migration can't proceed.
  2. Prepare: Azure creates a new virtual network gateway, public IP, and connections. This step can take up to 45 minutes. You can specify a name for the new gateway, or Azure will add _migrated to the original name by default. During preparation, the existing gateway is locked to prevent changes. If you need to stop the migration, you can abort at this stage, which deletes the new gateway and connections.

Note

The new gateway is created in the same region as the existing one. To change regions, you must delete the current gateway and create a new one in the desired region.

  1. Migrate: Switch traffic from the old gateway to the new one. This step can take up to 15 minutes and may cause brief connectivity interruptions.
  2. Commit: Finalize the migration by deleting the original gateway and its connections. If you need to cancel the migration, first switch traffic back to the original gateway by selecting the radio button in the Migrate section, then click Migrate, and finally choose Abort to delete the new gateway and its connections.

Important

After migration, validate your connectivity to ensure everything is functioning as expected. You can revert to the old gateway by selecting Abort after the prepare step, which will delete the new gateway and connections.

Limitations

The guided gateway migration experience has the following limitations:

  • ExpressRoute Only: The migration tool is designed for ExpressRoute virtual network gateways. It does not support VPN gateways or other gateway types. -Same Virtual Network Requirement: Migration is only supported within the same virtual network. Cross-subscription, cross-region, or cross-gateway-type migrations (for example, to/from VPN gateways) aren't supported.
  • No Downgrades: Downgrading from an Az-enabled SKU to a non-Az-enabled SKU is not supported.
  • GatewaySubnet Size: The GatewaySubnet must have a /27 prefix or longer to proceed with migration. For more information, see Create multiple prefixes for a subnet for more information.
  • Private Endpoint Connectivity: Private endpoints (PEs) connected via ExpressRoute private peering may experience connectivity issues during migration. Refer to guidance on mitigating these issues in the Private endpoint connectivity documentation. Private endpoint connectivity.
  • Legacy Gateways: ExpressRoute gateways created or connected to circuits in 2017 or earlier aren't supported.
  • Unsupported SKUs: Gateways using the "default" SKU aren't eligible for migration. To check the migration eligibility of your Gateway, there should be an Advisor notification.

For detailed troubleshooting errors and best practices, see Troubleshooting Gateway Migration.

FAQ

How do I add a second prefix to the GatewaySubnet?

Adding multiple prefixes to the GatewaySubnet is currently in Public Preview and supported only via PowerShell. For instructions, see Create multiple prefixes for a subnet.

How do I monitor the health of the new gateway?

Monitoring for the new gateway is the same as for the old gateway. The new gateway is a separate resource with its own metrics. During migration, you can also observe traffic patterns using the migration tool.

After migration, if you had existing monitoring, alerting, customer-defined maintenance windows, or diagnostic settings configured, you'll need to reconfigure these on the newly created gateway.

Will migration cause downtime?

Migration may cause a few minutes of downtime. Plan to perform the migration during a maintenance window to minimize impact.

How long can I wait before committing to the new gateway?

You have up to 15 days to commit after migration preparation. Use this time to validate connectivity and ensure all requirements are met before finalizing the migration.

How do I check if my gateway SKU is eligible for migration?

Azure Advisor will notify you if your gateway is eligible or requires migration. You can also check your ExpressRoute Gateway resource in the Azure portal—if your gateway is eligible, a banner at the top of the page will display the message "Implement Zone Redundant ExpressRoute Gateways."

Image showing Azure Advisor notification in overview of the gateway.

How do I validate if my gateway is Zone Resilient after migration?

To confirm your gateway is zone resilient after migration:

  • Check Azure Advisor: If your gateway is zone resilient, you will no longer see Advisor alerts recommending a zone-redundant gateway.
  • Verify resource tags: The migrated gateway will have a default tag labeled GatewaySKUMigration, indicating it has been moved to the zone-resilient deployment model.

These checks confirm that your gateway is now zone resilient.

Can I roll back this change?

Yes, until it is committed. The migration is composed of four major steps:​

  1. Validate – Confirms if your gateway is eligible for migration. ​ No changes at this stage; nothing to roll back​

  2. Prepare – Creates a new Virtual Network Gateway with the desired configuration. ​ The process can be aborted after step 2 and the new gateway will be deleted.​

  3. Migrate – Transfer the configuration from the existing gateway to the new one.​ If needed, the configuration can be reverted to the existing gateway after step 3.​

  4. Commit – Finalize the migration by decommissioning the old gateway and its connections. ​ Once the change has been committed, it can no longer be rolled back.

What is the traffic impact during migration? Is there packet loss or routing disruption?

During the migration process, traffic is rerouted seamlessly. There is no expected packet loss or routing disruption under normal conditions.

What should I do if the Prepare step fails due to a cross-region connection on a Basic SKU circuit during gateway migration?

If the Prepare step fails because your Basic SKU circuit has a cross-region connection, abort the gateway migration and upgrade the circuit SKU before trying again. This configuration is unsupported, and migration will continue to fail until the circuit SKU is upgraded.

Next Steps