Why does a request through Azure front door shows backend pool urls on the browser instead of frontends/domains?

Question

I have an azure front door which has custom frontends/domains, backend-pools, and routing rules configured to use azure web apps as backends. When i go the website the request passes through front door as it should and picks the best available backend, but it displays the azure webapp's url on the browser from the backend pool and not the azure front door domain. I expect to have the frontend/domain in the browser when i am directed to the backend and do not display the azure web app's url in the browser.

For example, when i go to www.mysite.com, i want it to be like www.mysite.com/foo (displaying the content from backend web app) and not mywebapp.azurewebsites.net/foo

Any guidance on how it can be achieved or is it possible to achieve?

Answer 1

The Azure front door just does a simple URL forwarding for the incoming client traffic. After my validation, if we select the forwarding protocol to HTTPS only, the address bar will not display the backend URL when you access the front door URL.

However, you actually still see the real backend domain in the set-cookie.

For more information, you could read the Backend host header and a similar question here1 and here2.