Issues with Front Door and the Origin host header

Rick Rader 0

I have AFD that uses an origin type of app services. I configure the host name that points to my web app service and that works fine. If I don't add the default domain that matches the host name, I get the error 404. My application login functionality doesn't work from the default domain, only when using the custom domain. How can I get around this issue? I tried leaving the Origin host header blank and adding in the custom but both result in the error 404.

KapilAnanth-MSFT 46,876 Reputation points Microsoft Employee

2024-06-24T05:41:14.2566667+00:00
@Rick Rader ,

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

I understand that you would like to configure Authentication with AFD in front of your App Service.

Your observation is correct. For Authentication to work, you should configure the custom domain in the Proxy (AFD).

See : Preserve the original HTTP host name between a reverse proxy and its back-end web application.

To answer your query,

You should add the custom domain to both AFD and the App Service

The DNS should point to the reverse proxy (AFD)

First, make sure you validate the domain with the Origin (App Service)

Then in AFD, use "Azure pre-validated domain" option

In case you are not using static webapps, you can still use the "Non-Azure validated domain" option

Note : Once the domain is validated in App Service, you can change the DNS to point to AFD

This way, the custom domain would still be valid in the App Service.

Hope this clarifies.

Thanks,

Kapil

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2 answers

Silvia Wibowo 3,986 Reputation points Microsoft Employee

2024-06-18T23:56:38.2566667+00:00

Hi @Rick Rader , I understand you use Azure Front Door in front of an App Service but you are having issues with Origin Host Header.

See the note from this document: If you're using an App Service as an origin, make sure that the App Service also has the custom domain name configured. For more information, see map an existing custom DNS name to Azure App Service.

If you've configured custom domain name on your App Service, you can either leave Origin Host Header blank or fill it in with custom domain.

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Rick Rader 0 Reputation points

2024-06-19T00:46:16.9+00:00

How can I add the custom domain to both AFD and the App Service? Or if I have the custom domain configured on my App Service who is DNS directing traffic via the AFD endpoint?

Silvia Wibowo 3,986 Reputation points Microsoft Employee

2024-06-19T23:52:23.9233333+00:00

Hi @Rick Rader , DNS mapping of your custom domain will point to AFD endpoint. However, since your application has host header check to allow login, you also need to configure custom domain on your App Service.

Client, accessing custom domain -> DNS lookup, point to AFD endpoint -> AFD, set origin with default App Service domain and either leave Origin Host Header blank or fill it in with custom domain -> App Service

Silvia Wibowo 3,986 Reputation points Microsoft Employee

2024-07-05T03:52:05.9933333+00:00

Hi @Rick Rader , any update?
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hossein jalilian 8,160 Reputation points

2024-06-18T23:59:32.5933333+00:00

Thanks for posting your question in the Microsoft Q&A forum.

You need to ensure that the correct host headers are configured in AFD.

In the Azure portal, navigate to your AFD resource. under Settings, click on Origin groups.

select the origin group associated with your App Service. under Origins click on the origin representing your App Service. in the Origin blade, ensure that the Host header field is set to the default domain of your App Service.

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Rick Rader 0 Reputation points

2024-06-19T00:44:41.52+00:00

my app doesn't allow users to login from the default domain, so when I moved the custom domain to AFD and put the default domain in the host header field it now behaves as if I'm accessing from the default even though it's using the custom domain.
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Issues with Front Door and the Origin host header

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