AFAIK, in Site to Site VPN with Azure, there is no NAT, clients in Azure/On-premise have to see directly the clients in Azure/On-premise. It's a Site-To-Site VPN, clients will not make difference between the network in the LAN or in the other site LAN
Regards, Samir Farhat Infrastructure and Virtualization Consultant Virtualization, Cloud, Azure ? Follow this blog https://buildwindows.wordpress.com/