You might recall that Tor is restricting the possible amount of Tor relays per IP address to 2, mainly for Sybil prevention reasons. Given that Tor on the relay side at least is not multithreaded yet (and will likely not be for the near and medium future) that's wasting a lot of useful resources as many servers can easily handle more than 2 relays. Additionally, IPv4 addresses are scarce/expensive.
I have good news for you, though. Thanks to a push by our relay operator community we raised that limit to 4 with the help of the directory authorities (by having set `AuthDirMaxServersPerAddr 4` on a majority of them) and, depending on how that experiment goes, consider raising it even to 8.
Thus from now one should be able to run 4 relays per IP address. We are looking very much forward to seeing a bunch of additional relays entering the network and making it stronger.
For more details, information and discussion see: tor#40744.
 proposals/109-no-sharing-ips.txt · main · The Tor Project / Core / Tor Specifications · GitLab
 Increase the amount of allowed relays per IP address (#40744) · Issues · The Tor Project / Core / Tor · GitLab