Received invalid status code: 403 in the backend server’s HTTP response for my app gateway

Question

Im very new to azure app gateway im trying to replicate the same content which is showing for https://azdev8-dsm.testwd.com/Registration/Guest/Registration.htm it should show same when i access the https://azagw-dsm.testwd.com/Registration/Guest/Registration.htm .

so ,I have created backend pool as below IP address or FQDN : wd-az-asp-dev8-webservice.azurewebsites.net

• custom domain mapping to dedicated app gateway has already taken care by IT team.
• Redirection rules:

My backend health shows as follows:

when i browse azagw-dsm.testwd.com/Registration/Guest/Registration.htm im getting as below

Note: Mistakenly I just removed the custom domain (azagw-dsm.testwd.com) from ** wd-az-asp-dev8-portal** . From that point im facing this error. Before that it was worked as expected.

Can any one help me on this pls

Thanks in advance

Santosh.Pingali

Answer 1

Hello Santosh Pingali

Greetings!
I understand that you are receiving the 403-status code. However, when accessing the application gateway URL, you will encounter a 502 error.

Based on your scenario, we observed that you are receiving a 502 error when trying to access the application gateway URL. From the health snapshot you provided, we understand that your backend is unhealthy, which is causing the 502 error.

We also noticed that the backend web app URL "wd-az-asp-dev8-webservice.azurewebsites.net" is returning a 403 error for the application gateway request, marking the backend health as unhealthy.

Could you please check if there are any network restrictions configured on the backend web app. If so, please allow the application gateway to reach the web app. This should result in a 200 response instead of 403, and the system will work as expected.

And let me know (azagw-dsm.testwd.com) this belongs to which resource.

Check the reference doc: Azure App Service access restrictions

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Hope the above answer helps! Please let us know do you have any further queries.

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