This plugin provides the command /dupeip. The commands shows the admins a list of all users who are using the same IP address. These users are probably logged in more than once then. That's how the output of the command looks like:
Following users have the same IP address: [User1*Guest2 <12.34.56.78>] [User3*Guest4*User5 <21.43.65.87>]
Following users have the same IP address: [User1*Guest2 <12.34.56.78>] [User3*Guest4*User5 <21.43.65.87>]
