Since March 2004, Google gives less value to the links come from pages with similar IP to yours, so do not need to cheat to change your PageRank and therefore improve your SEO: Google knows.
A filter this switch is called PageRank Hilltop algothim
Google has implemented this change in their algorithm to neutralize a trap that some experts in SEO webmasters have been doing since the PageRank became operational: to create endless small web, hosted on your own ISP, that link to your main website.
Also large corporations have abused the fact that a large number of inbound links you make to improve the positioning ... without going any further, SoloStocks we have links in the footer to all websites Intercom Group... and therefore on all pages Softonic (To quote one of our companies) there is also a link to SoloStocks. Since We have over 500,000 pages indexed in Google, my site receives 500,000 external links. Thing seems to me great ... but that is not 100% just from the point of view of an independent webmaster who runs a website with great content but never positioned above mine ... Google has implemented until Hilltop It has neutralized the effect of the links.
So I said ... do not need that to improve the SEO of your website, waste time including links to websites that are hosted on the same IP you ... because Google now looks at the IP from coming inbound links and has lowered the weight will greatly which have a similar IP to yours.