You can configure integration between a web app and your virtual network, with this feature you can allow for example a connection to your SQL Server running on a virtual machine.
More details you can find here.
The integration required a dedicate subnet.
These are the steps to make a virtual network integration:
- In your web app click search for Network and click on VNet-Integration:
- +Add Vnets, select your subscription and the virtual network and OK:
It is done! Now your web app can access your resources inside your virtual network!