Azure application gateway as backend pool of F5 VS

Hi All,

I am facing an issue with the below setup and need some guidance.

Architecture:

Internet Client → F5 VIP → Azure Application Gateway (Internal IP) → Backend Application

The requirement is to publish the application through F5, where the backend pool member is the internal IP address of an Azure Application Gateway.

Issue:

If I configure the F5 pool health monitor as TCP, the pool member becomes UP.

If I configure the health monitor as HTTP or HTTPS, the pool member remains DOWN.

Accessing the Azure Application Gateway directly (using its internal IP and required hostname) works successfully.

The issue only happens when traffic passes through F5.

SSL/TLS Configuration:

SSL certificate is configured on F5 VIP.

The same application certificate is also configured on Azure Application Gateway listener.

Hostname used by the application

We have already tried server SNI configuration on F5 and multiple SSL profile settings, but the issue is not resolved.

Troubleshooting already performed:

Verified Azure Application Gateway backend configuration.

Confirmed Application Gateway listener and certificate are working when accessed directly.

Tested F5 TCP health monitor successfully.

Tested HTTP/HTTPS monitors from F5, but they fail.

Raised a case with F5, and they advised checking from the Azure Application Gateway side.

Appreciate your support.