To enable a web app hosted in Azure App Service to connect securely to an on-premises SMB share (Share1), you must create hybrid network connectivity between your Azure environment and your on-premises network.
According to the Microsoft Azure Administrator Study Guide and Microsoft Learn documentation, Azure Web Apps running in an App Service Plan cannot directly access on-premises file shares over the public internet for security reasons. You must extend your on-premises network to Azure through a Virtual Network (VNet) and then integrate the web app with that network.
The Virtual Network Gateway is the component that enables this hybrid connectivity. It establishes a Site-to- Site VPN or ExpressRoute connection between the Azure VNet and the on-premises network, allowing the web app (after VNet integration) to access internal resources such as SMB shares, SQL Servers, or file servers.
Once the VPN gateway is configured and the web app is integrated with the VNet (Regional VNet Integration), the web app can securely access Share1 over the private network channel.
Official Microsoft Documentation Extract (Summary):
"To access on-premises resources from Azure App Service, configure VNet Integration and establish a Site-to- Site VPN or ExpressRoute connection using a Virtual Network Gateway. This allows Azure resources to securely communicate with on-premises systems such as SMB file shares or databases." (Source: Microsoft Learn - Connect an App Service app to an on-premises network using Azure VPN Gateway.)