Link farming with the same IP is useless. There are several ways to really go about doing this. The easiest would be to purchase several domains, and put them on different hosting companies throughout the world.
If you really want to run a proper link farm, don't know why, but you cannot have the interlinking on the same IP C class.
Also, mask our whois information. Remember Google is a registrar now, so they see everything.
Also, no freaking footprints. That means, don't use the Googel Adsense across your whole network, or do something like have 1 Google Analytics account for all your domains to check traffic. Don't link your google analytics accounts, NEVER login to your different Google Analytics account from the same IP. Safe bet on staying under the radar is don't use any google products on any of your domains.
No foot prints. interlink in an open linkwheel motion, Meaning, all sites link to another, but at the end, don't link to the first site. All sites have to be on different hostings, and different IP Class.
Use web 2.0 properties to boost your web sites as well. If you play it safe, you'll have yourself a notice solid, almost undetectable link farm. Again, I don't even know why you want a link farm, but that's what I recommend when attempting this.