I have been driving a project which most of the components are run on Azure as PaaS and others as IaaS. Due to a service dependency, we built a point to site vpn to connect our Apps to our Azure VNet, and a site to site vpn to connect our VM‘s to to our on-premise. So our Apps are able to communicate to our on-premise through the tunnels. Lastly, we defined a custom DNS server ip address which points to one of our dns servers that run on our on-premise.
The custom dns setting inherits the VM’s inside the VNet. But not for the App.
At this point, we ran into a problem.Although the custom dns server ip address was set and displayed in VNet integration blade, it didn’t effect our App! After a short dialog with Azure Support we were provided a solution :)
As you can see above , we added a variable settings under the Application Settings of our web app. The value, of course, points to our on-premise dns server. The support guy that helped us gave us a promise to update the documentation :)
Wish you great week:)