rcmds.banip/banip allows for IP addresses to be blocked from connecting to the server. The (player/IP) argument will
accept a player name, offline or online, or an IP address. If given a player name, it will find the player’s last IP
address and ban it. If given an IP, it will ban the IP.
/banip 1.2.3.4 - Bans the IP 1.2.3.4.
/banip Notch - Bans Notch’s last IP.
This command supports online name-completion.