403 response from App service after routing traffic from Azure Front Door

Question

I am trying to set up a Front door for an app service. The goal here is allow traffic to the App service only from the Front door .

But once I restrict the app service networking to allow access only from the Front door , I keep getting error 403 when accessing the app service Front door URL.

Here's App Service network restriction

Answer 1

@Jagruti Mohanty ,

Welcome to the Microsoft Q&A Platform. Thank you for reaching out & I hope you are doing well.

I understand that you are facing 403 error with your Application behind Azure Front Door.

• I see that your App Service application uses Azure Entra Authentication
• And you are accessing the AFD via the default domain.
• This is not recommended, see Preserve the original HTTP host name between a reverse proxy and its back-end web application
• Your exact situation is documented here
• I would suggest you use a custom domain name across both App Service and AFD to circumvent this issue

Please let us know if we can be of any further assistance here.

Thanks,

Kapil

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