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Copy file name to clipboardExpand all lines: articles/expressroute/gateway-migration.md
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ms.service: azure-expressroute
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ms.custom: ignite-2023
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ms.topic: concept-article
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ms.date: 03/31/2025
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ms.date: 05/19/2025
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ms.author: duau
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---
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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, selecting the appropriate [gateway SKU](expressroute-about-virtual-network-gateways.md#gateway-types) is crucial. Higher-level SKUs allocate more CPUs and network bandwidth to the gateway, enabling higher network throughput and more reliable connections to the virtual network.
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### Available SKUs for ExpressRoute Virtual Network Gateways
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The following SKUs are available:
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-**Standard**
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-**HighPerformance**
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-**UltraPerformance**
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-**ErGw1Az**
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-**ErGw2Az**
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-**ErGw3Az**
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-**ErGwScale** (Preview)
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### Availability Zone-Enabled SKUs
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The SKUs **ErGw1Az**, **ErGw2Az**, **ErGw3Az**, and **ErGwScale** (Preview) are referred to as Availability Zone (Az)-Enabled SKUs. These SKUs support deployment across multiple availability zones, providing enhanced resiliency and high availability by distributing the gateway infrastructure across zones.
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In contrast, the **Standard**, **HighPerformance**, and **UltraPerformance** SKUs, also known as non-Az-enabled SKUs, are typically associated with Basic IPs and don't support distribution across availability zones.
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### Recommendation for enhanced reliability
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For improved reliability, we recommend using an Az-enabled virtual network gateway SKU. These SKUs support zone-redundant configurations and are associated with Standard IPs by default. A zone-redundant setup ensures that the gateway infrastructure remains operational even if one availability zone encounters an issue. To learn more about zone-redundant gateways, see [Availability Zone deployments](../reliability/availability-zones-overview.md).
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## Gateway migration experience
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Previously, migrating between SKUs required using the `Resize-AzVirtualNetworkGateway` PowerShell command or manually deleting and recreating the virtual network gateway.
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The guided gateway migration experience simplifies this process by allowing you to deploy a second virtual network gateway within the same GatewaySubnet. Azure automatically transfers the control plane and data path configurations from the old gateway to the new one. During the migration, both gateways operate simultaneously within the same GatewaySubnet. While this feature minimizes disruption, brief connectivity interruptions might still occur.
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Once the migration is complete and the old gateway along with its connections are deleted, the newly created gateway is tagged with `"CreatedBy : GatewaySKUMigration"`. This tag helps distinguish migrated gateways from others that haven't undergone migration and shouldn't be deleted.
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### Steps to migrate to a new gateway
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1.**Validate**: Ensure all resources are in a succeeded state to confirm the gateway is ready for migration. If prerequisites aren't met, validation fails, and you can't proceed.
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2.**Prepare**: Create a new Virtual Network gateway, Public IP, and connections. This operation can take up to 45 minutes. You can choose a preferred name for the new gateway and connections. If you don't change the name, the tag **_migrate** will be appended by default. During this process, the existing Virtual Network gateway will be locked, preventing any creation or modification of connections.
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3.**Migrate**: Select the new gateway to transfer traffic from the old gateway to the new one. This operation can take up to 15 minutes and may cause brief interruptions.
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4.**Commit**: Finalize the migration by deleting the old gateway and connections.
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> [!IMPORTANT]
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> 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.
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.
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## Supported Migration Scenarios
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-**ExpressRoute Only**: The migration tool is designed for **ExpressRoute virtual network gateways**. It does **not** support VPN gateways or other gateway types.
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-**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.
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-**No Downgrades**: Downgrading from an **Az-enabled SKU** to a **non-Az-enabled SKU** is **not** supported.
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-**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](https://learn.microsoft.com/en-us/azure/virtual-network/how-to-multiple-prefixes-subnet) for more information.
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-**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](../virtual-network/virtual-network-manage-subnet.md) for more information.
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-**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](expressroute-about-virtual-network-gateways.md#private-endpoint-connectivity-and-planned-maintenance-events).
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-**Legacy Gateways**: ExpressRoute gateways created or connected to circuits in **2017 or earlier** aren't supported.
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-**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.
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For detailed troubleshooting errors and best practices, see [Troubleshooting Gateway Migration](gateway-migration-error-messaging).
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For detailed troubleshooting errors and best practices, see [Troubleshooting Gateway Migration](gateway-migration-error-messaging.md).
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## Gateway migration experience
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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.
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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.
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### Steps to migrate to a new gateway
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1.**Validate**: Check that all resources are in a succeeded state. If any prerequisites aren't met, validation fails and migration can't proceed.
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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 **_migrate** 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.
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|--|--|
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| Basic IP | Standard IP |
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## Common Validation Errors
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## FAQ
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### How do I add a second prefix to the GatewaySubnet?
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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](../virtual-network/virtual-network-manage-subnet.md).
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### How do I monitor the health of the new gateway?
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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.
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### Will migration cause downtime?
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Migration may cause a few minutes of downtime. Plan to perform the migration during a maintenance window to minimize impact.
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### How long can I wait before committing to the new gateway?
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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.
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During the gateway migration process, it's essential to validate whether your resources are ready for migration. Below are some common validation errors you can encounter:
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### How do I check if my gateway SKU is eligible for migration?
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### Virtual Network
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Azure Advisor notifications will alert you if your gateway requires migration. Attempting to migrate an ineligible gateway will result in an error. For more details, see [Troubleshooting Gateway Migration](gateway-migration-error-messaging.md).
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-**MaxGatewayCountInVnetReached**: This error indicates that the maximum number of gateways allowed in the virtual network was reached.
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## Next Steps
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- Troubleshoot migration issues with [Troubleshooting Gateway Migration](gateway-migration-error-messaging.md).
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- Learn how to [migrate using the Azure portal](expressroute-howto-gateway-migration-portal.md).
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- Learn how to [migrate using PowerShell](expressroute-howto-gateway-migration-powershell.md).
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- Explore best practices for [designing for high availability](designing-for-high-availability-with-expressroute.md).
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- Plan for [disaster recovery](designing-for-disaster-recovery-with-expressroute-privatepeering.md) and [using VPN as a backup](use-s2s-vpn-as-backup-for-expressroute-privatepeering.md).
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- Explore best practices for [designing for high availability](designing-for-high-availability-with-expressroute.md).
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