Ensuring Outbound Rules of Azure App Service

In situations where Azure App Service is configured with network protection, it is crucial to know which systems and applications have access to the App Service, and which applications and systems can be accessed from the App Service (outbound). This blog explains a simple but useful trick that can be used to check the outbound rules of the App Service.

Prerequisites: Azure App Service with restricted internet access

Go to the Azure portal, open the App Service, and click on the Console under Development tools.

Type the tcpping command followed by the IP address or URL of the application that needs to be accessed from the App Service.

When internet access is restricted from the App Service, the result for the tcpping www.google.com command will appear as shown below. (Connection attempt failed) 

Enable internet access from the App Service and try the same command again to ensure the outbound rules are configured correctly. Now the App Service can access the specified application or system.

Likewise, the command can be used to test communication/access from the App Service to an application in the same network or different VNETs.