Forum Moderators: phranque
It looks like you are heading down the wrong path based on a mis-diagnosis.
Your other thread shows an invalid robots.txt.
Start with a valid robots.txt. That will work for well behaved spiders. You should only resort to IP cloaking for mis-behaved spiders after you find that they do not obey a valid robot.txt file. If the spiders you are trying to block are from major search engines, then they will obey the robots.txt and you will not have to resort to the trickier methods you are asking about here.