I have seen in my ARM template that this properties is available in the virtual network gateway.
However, the documentation does not seem to explain how to use it.
What I need is to create a virtual network gateway with OpenVPN point to site (up to this point, no problem, it is really easy) BUT I need to be able to configure static IPs for the clients.
The privateIPAllocationMethod look promising but I would expect to see further configuration to describe which client gets which IP.
Any clue?