Unable to access api exposed over VM through azure apim

Question

We have an application running on azure virtual machine that doesn't have a public ip address.
We connect to VMs and other services on azure using existing VPN connection as established by the admin.

That application on the virtual machine exposes the back-end functionalities using REST API.
Testing the same using curl or api testing tool like Postman is successful as shown in below image:

Note above image is testing the api exposed from Virtual machine application directly.

Now, we want to expose the api through azure apim. We have done the configuration as shown in image below:

If we test it in apim with same parameters that worked when we tested api directly show this:

It shows testing successful with 200 response code. However, we dont get the actual response like "user has successfully logged in". Even if we pass wrong parameters that should not be successful, it still shows successful with 200 response code.
We tested using curl command and also postman and got 200 response code:

It doesn't matter what parameters we pass, it gives 200 response code. Not sure what we are missing, can someone please suggest?
I am attaching a document which shows the complete trace output.
191409-apim-trace.pdf

Thanks in advance

Answer 1

Hi, @Sumit Bharti

I think you need to connect to VNET in External Mode in your scenario. The following will be helpful, but is it set like this?
https://learn.microsoft.com/en-us/azure/api-management/api-management-using-with-vnet?tabs=stv2

Second, I couldn't see the operation settings from your settings.
Can you see the access log of the origin (backend) server when you submit the request?

Answer 2

We allowed traffic from the APIM subnet's IP Address range to the NSG rules attached the subnet of the virtual machine.
This fixed the issue.