I suggest expand all IP-related columns size from varchar(15) to varchar(31).

And grab the "X-Forwarded-For" parameter , and append to the IP address. So that Admins can easily trace where users truly come from.

An example will be "123.123.123.123,234.234.234.234"
Which means the user is behind the proxy of 123.123.123.123 , and his true IP is 234.234.234.234

English is not my native language. I try my best to express my thought precisely. I hope you understand what I mean. If any misunderstanding results from culture gaps, I apologize first.