Use Public IP address with custom DNS label on existing Application Gateway
The Application Gateway does not allow to get a public IP address assigned, for which the DNS label has been set.
Error Message: "You can't choose a public IP address that has a domain name label specified."
When using certificates that are registered on specific CNAMEs, you should be able to set the DNS label of the public IP address of the Application Gateway to match the CNAME.
Thanks for your feedback. Support in portal for this scenario has been started currently. We expect this to be available over next few weeks.