I run several different web pages on different servers (with different IP addresses). These pages are linking to each other in order to boost number of backlinks pointing to my pages.
I would like to move all those projects to a single virtual host (with a single IP address). My question is, how Google handles links within different domain names but same IP address. Is there some penalization for it? Could this lead to lower PageRank?
Actually, it's hard to say.
Google could consider these backlinks as attempts to increase PageRank and thus manipulate search rankings because the websites with the same IP address (the same server) are most probably from the same webmaster or company.
However, Google can't say these backlinks are useless for SEO (or can penalize websites) because in shared hosting, many websites have the same IP address and it's possible that one of these websites links yours. Moreover, even if the two websites have the same IP address (and are from the same webmaster or company), it can be relevant for visitors to link one to the other (for example if these two websites are related to the same theme).
In any case, Google can't be sure to be able to judge without analyzing other factors.
That's why I think it can be useful for SEO to link a website to another (even if the two websites have the same IP address) but you need to take precautions as following:
There is no penalty for as long as you don't overdo it. Just two domains on same server? Not even near the amount I'd say would be questionable. Two could be coincedence, would be very mean to penalize that.
It has a bigger values wether or not you share a lot of domains on 1 IP address, or if you share an IP address with malicious sites.
It's just two sites with backlinks, if you want to work on your ranking in this area, create methods for other sites to backlink naturally, via your visitors.
