dns server set azure public ip address as first in order

Author: schaffererin

articles/aks/private-clusters.md

@@ -26,7 +26,7 @@ Private cluster is available in public regions, Azure Government, and Azure Chin
 * The `aks-preview` extension 0.5.29 or higher.
 * If using Azure Resource Manager (ARM) or the Azure REST API, the AKS API version must be 2021-05-01 or higher.
 * Azure Private Link service is supported on Standard Azure Load Balancer only. Basic Azure Load Balancer isn't supported.  
-* To use a custom DNS server, add the Azure public IP address 168.63.129.16 as the upstream DNS server in the custom DNS server. For more information about the Azure IP address, see [What is IP address 168.63.129.16?][virtual-networks-168.63.129.16]
+* To use a custom DNS server, add the Azure public IP address 168.63.129.16 as the upstream DNS server in the custom DNS server, and make sure to add this public IP address as the *first* DNS server. For more information about the Azure IP address, see [What is IP address 168.63.129.16?][virtual-networks-168.63.129.16]
 
 ## Limitations