ZeroTier operates a public (no authentication required) virtual network called Earth with the network ID
8056c2e21c000001. This network is primarily used for testing, though a number of gamers and other casual users use it for peer to peer communication.
Earth will assign you a private IPv6 address and an IPv4 address in the unused
22.214.171.124/7 region of the IPv4 address space. This region officially belongs to the US DOD and is not routed on the public Internet. You can use pseudo-private ranges like this on your own virtual networks too, but we do not recommend it for production systems. If these ranges ever are advertised publicly networks using them would have to re-number.
After joining visit earth.zerotier.net. You can ping this host as well to test connectivity.
If you join this or any other public network, make sure your computer is up to date on all security patches and you've stopped, locally firewalled, or password protected all services on your system that listen for outside connections. Public networks are "party lines."