ZeroTier is great, but hosting the server is very complicated (I'm not going to stop using it now, since it's so easy and is already set, but it's good to know of alternatives).
It's based on Snabb, a user-space networking platform, so it'll need direct hardware access and supports only a few specific NICs. But in exchange for that, it should be really fast.
ZeroTier is great, but hosting the server is very complicated (I'm not going to stop using it now, since it's so easy and is already set, but it's good to know of alternatives).