I have an App service plan with 3 app services with private endpoint, call from app service B to app service C fails with 403 forbidden error

Question

I have an app service plan with 3 app services with Private endpoints for all the 3 apps. Front end calls--> Middleware calls --> back end

calls from Middleware to back-end fails, I don't see any error in the Application logs or log stream of the Middleware, just a log message which says the back end is called.

When I access the backend url directly from the browser I get a response. e.g https://backend.azurewebsites.net/hello response "Hello"

From kudu bash of the middleware when I try tcpping backend.azurewebsites.net:443 I get Bad destination address curl command to the backend from middleware fails with 403 Forbidden Error curl https://backend.azurewebsites.net/hello --> 403 Forbidden Error.

Middleware is Docker container on Linux, Backend run time stack Java 8, Java Web Server Stack - JAVA SE (Embedded Web Server) on Linux

Any guidance on what I'm missing here would be a great help.

Answer 1

Private Endpoint is only used for incoming flows to your Web App.

Outgoing flows will not use this Private Endpoint, the outgoing flows from app services can be routed through your VNET by using the VNET integration feature.

Please refer the link

https://learn.microsoft.com/en-us/azure/app-service/networking/private-endpoint

https://learn.microsoft.com/en-us/azure/app-service/web-sites-integrate-with-vnet#enable-vnet-integration