OpManager Enterprise - Type of connection between Central and Probe

OpManager Enterprise - Type of connection between Central and Probe

Hello everybody,
what type of connection is needed to allow the central to communicate with the probe? Is any internet connection sufficient or must the two private networks communicate with each other, for example via VPN or a layer 2 extension?

Central>>>internet (public IP)>>>Probe
or
Central>>>VPN/L2 extension (private IP)>>>Probe

Thank you, Regards