Salts are only useful when you already know which hash to check e.g. because the user supplied the username that picks which password hash to check. When matchi

Salts are only useful when you already know which hash to check e.g. because the user supplied the username that picks which password hash to check. When matching an IP against a list of salted hashes, you need to hash the input with every possible salt to compare against all hashes in the list. So for performance reasons, it's probably not feasible to use more than one salt (or a small number of salts). Then it's again very possible to reverse the list of salted hashes because the search space is number of all IP addresses times number of salts used, which is way less than the number of all hashes.