Update public-ip-upgrade-vm.md

CSS has received multiple cases where customers report that the script does not account for NICs assigned to the AppGW backend pool.
If a NIC with a Basic Public IP is upgraded using this script, it will be removed from the AppGW backend pool.
Customers must manually reassign the NIC after the script runs — but many are unaware of this until it's too late.
Therefore, I strongly recommend adding this Q&A to the MS Learn page to help prevent confusion and reduce support cases.

Author: maotsuk

articles/virtual-network/ip-services/public-ip-upgrade-vm.md

@@ -108,6 +108,11 @@ There is no way to evaluate upgrading a Public IP without completing the action.
 
 Yes, the process of upgrading a Zonal Basic SKU Public IP to a Zonal Standard SKU Public IP is identical and works in the script.
 
+### If I specify a NIC associated with a public IP targeted for migration in the AppGW backend pool, will this script remove it from the pool?
+
+Yes, it will be removed. After running the script, you will need to manually reassign the NIC to the AppGW backend pool.
+Alternatively, you can avoid this issue by explicitly specifying the private IP address in the backend pool configuration before migration.
+
 ## Use Resource Graph to list VMs with Public IPs requiring upgrade
 
 ### Query to list virtual machines with Basic SKU public IP addresses