What is the goal? Are you looking for a specific IP? Or are you wanting to know what IPs have been used by a specific user?
If you are running MySQL 5.6.3 or higher then this function should work:
Code:
SELECT INET6_NTOA(ip) AS ipaddress
FROM xf_ip
Otherwise there isn't an easy way to query the readable IP since XF started supporting IPv6 addresses.