Loopback is actually 127.0.0.0/8. You have 16,777,214 addresses (127.0.0.1 through 127.255.255.254) to play with.
Try it out! For example, ping 127.87.123.7 and you should get replies with approaching-zero latency.
Voxel stores your waypoints by hostname and port. If you use a DNS name, it uses that instead of an IP. It omits the port if you use (either implicitly, or explicitly) the default.