There is a plugin like this out there. I cannot remember how I found it, but I used it a long time ago. It goes like this and exactly like this. Anyone with the * Permission or that is OPed cannot join the server without their IP being approved. Your IP can only be approved in the console. approve xitroxide 00.00.11.00 will approve xitroxide for that certain IP. If the IP is different it won't work. If anyone knows of this plugin please send me it!