block non-AZ SKU” - Update VPN Gateway SKU migration information

Added details regarding the migration of non-AZ VPN Gateways and the implications of the 'block non-AZ SKU' rollout, including error handling and migration steps.

Author: raboilla

articles/vpn-gateway/gateway-sku-consolidation.md

@@ -92,6 +92,32 @@ Using the Standard SKU public IP address parameter with a VPN Gateway Basic SKU
 
 Standard and HighPerformance gateway will be migrated to AZ gateways in CY26. For more information, see this [announcement](https://azure.microsoft.com/updates/standard-and-highperformance-vpn-gateway-skus-will-be-retired-on-30-september-2025/) and [Working with VPN Gateway legacy SKUs](vpn-gateway-about-skus-legacy.md).
 
+### What happens to existing non-AZ VPN Gateways after the “block non-AZ SKU” rollout starting in February'26?
+### I have an existing VPN Gateway using a non-Availability Zone (non-AZ) SKU (VpnGw1–VpnGw5). What changes after this rollout?
+
+After the “block non-AZ SKU” feature flag rolls out, existing VPN Gateways using non-AZ SKUs will no longer allow configuration changes. If you attempt any management or configuration operation on a non-AZ gateway, you will receive a ValidationException. This is expected behavior after the rollout.
+
+### Why am I seeing a ValidationException? example error message: Microsoft.WindowsAzure.Networking.Nrp.Frontend.Common.ValidationException: VpnGw1-5 non-AZ SKUs are no longer supported for VPN gateways. Only VpnGw1-5AZ SKUs can be created going forward
+
+The exception indicates that configuration changes on non-AZ VPN Gateway SKUs are no longer supported. To proceed, the gateway must first be migrated to an equivalent Availability Zone–enabled (AZ) SKU.
+
+### What action is required to resolve this error?
+
+You must migrate your VPN Gateway from a non-AZ SKU to the corresponding AZ SKU before making any other changes.
+For example:
+
+VpnGw1 → VpnGw1AZ  
+VpnGw2 → VpnGw2AZ  
+
+### Will migrating to an AZ SKU cause downtime?
+
+Same SKU family migration (for example, VpnGw1 → VpnGw1AZ) is non-disruptive and is a metadata-only change.  
+Cross-family migration (for example, VpnGw1 → VpnGw3AZ) is disruptive, consistent with existing VPN Gateway resize behavior.  
+
+### Do AZ SKUs automatically become zone-redundant?
+
+AZ SKUs are AZ-capable. They become zone-redundant only in regions that support Availability Zones, as described in the [existing documentation](https://learn.microsoft.com/en-us/azure/vpn-gateway/gateway-sku-consolidation#will-there-be-any-performance-impact-on-my-gateways-with-this-migration)
+
 ## Next steps
 
 For more information about SKUs, see [About gateway SKUs](about-gateway-skus.md).