Remote Desktop solution for Linux machines ruing Gnome3

I'd like to do Remote Desktoping on a Linux ruing machine from a Linux machine, both ruing gnome3. What are please the easiest to configure, but still secure, solutions?

I'm not sure I'll be able to configure the host router. So far the only solution coming to mind is NoMachine (as soon as they release NoMachine Network, formerly knows as NoMachine Anywhere), which doesn't require router setup.

Thanks for any suggestion :)