App service gateway IP shows This site can’t provide a secure connection Diagnostics. ERR_SSL_PROTOCOL_ERROR

I am trying to create application gateway for an Azure app service. I configured everything accordingly. I did not use custom domain. I want to configure with azure app service default domain. I followed a couple of videos on youtube:

• https://www.youtube.com/watch?v=1HG_TKG468w
• https://www.youtube.com/watch?v=DjNPHetdlQo&list=PLd-NoD4_fUJJtrUzRnTOEJRBtHLz5IRV9

I tried to create a app gateway and now it shows the following error

This site can’t provide a secure connection app120.azurewebsites.net sent an invalid response. Try running Windows Network Diagnostics. ERR_SSL_PROTOCOL_ERROR

I tried the possible ways for clearing this issue. Which are:

Clearing Browser cache. Reset system time Flushing DNS cache Clear SSL state Disable antivirus Delete Host file

But none of them solved my problem. Also please provide the process to create app gateway for the azure app service for default domain.

I tried the same in my environment I got the same error like below:

Created Application gateway with backend pool and http setting like below:

Associate rule with listener and backend setting :

Make sure to add service endpoint in virtual network like below:

Check your backend status is healthy like below:

Note that: According to MsDoc default domain may not work always as there are limitations. If your backend status is in healthy state Application Gateway IP Address will redirecting to app service URL, for this case you can use custom domain to avoid any potential issues It's also possible that there might be transient issues that resolve themselves over time.

In app service -> configuration -> General settings -> HTTPS Only is turned on like below:

When I hit the public IP got result successfully like below:

References:

Manage traffic to App Service - Azure Application Gateway | Microsoft Learn

Host name preservation - Azure Architecture Center | Microsoft Learn