I have an App Service (A) in the customer’s directory with outbound VNet integration enabled. We also have a license App Service (B) in our directory. When App Service (A) tries to send a request to App Service (B), it fails, even though App Service (B) h

Hi @Dhivya s
To establish a connection between App Service (A) and App Service (B) across different directories, you need to ensure that the outbound VNet integration is configured correctly.

Ensure that there are no NSGs blocking outbound traffic from App Service (A) to App Service (B). Since App Service (B) does not have any restrictions, the issue may lie in the configuration of the NSGs associated with the virtual network of App Service (A).

If App Service (B) is secured with service endpoints or private endpoints, ensure that App Service (A) is configured to access these endpoints. This can help facilitate communication without being restricted by public IP address limitations.

If there are issues related to SNAT port limitations, consider using a NAT gateway for App Service (A). This will provide a stable outbound IP address and increase the number of available outbound SNAT ports.

Ensure that any cross-domain access policies are correctly configured, allowing App Service (A) to communicate with App Service (B).

Check the application settings and configurations of both App Services to ensure that they are set up to allow communication between them.

References:

• App Service networking features
• Azure security baseline for App Service
• Troubleshoot intermittent outbound connection errors in Azure App Service What specific error message do you receive when App Service (A) tries to connect to App Service (B)? Can you confirm whether both App Services are set to the required pricing tiers that support VNet integration?
  Let me know if you have further assistances needed.