Update key-vault-certs.md

Author: jaesoni

articles/application-gateway/key-vault-certs.md

@@ -12,6 +12,9 @@ ms.author: mbender
 
 # TLS termination with Key Vault certificates
 
+> [!IMPORTANT]
+> Starting **August 31, 2025**, all clients and backend servers interacting with Azure Application Gateway must use Transport Layer Security (TLS) 1.2 or higher, as [support for TLS 1.0 and 1.1 will be discontinued](https://azure.microsoft.com/updates/azure-application-gateway-support-for-tls-10-and-tls-11-will-end-by-31-august-2025).
+
 [Azure Key Vault](/azure/key-vault/general/overview) is a platform-managed secret store that you can use to safeguard secrets, keys, and TLS/SSL certificates. Azure Application Gateway supports integration with Key Vault for server certificates that are attached to HTTPS-enabled listeners. This support is limited to the v2 SKU of Application Gateway.
 
 Application Gateway offers two models for TLS termination: