Access to Website hosted on Azure VM.

Hi,

I have my website on IIS 8 server hosted on a Azure Virtual Machine. Which has a Public IP  23.102.157.xxx  and aInternal IP 10.0.0.4. The website is on example.cloudapp.net

I want to add a firewall inbound rule on my server which allows requests from this website on that's on Azure VM. 

What is the IP address I would have to give to allow only requests from this website hosted in Azure VM. Is it possible? If not any alternatives on what im doing wrong?

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