Don't rely on links from domains on the same IP

While Google doesn't discriminate against domains that have the same IP (for example, domains that use virtual hosts), other search engines may. So it's best to avoid trying to increase your inbound links with links from other domains that you own. The same is true for domains hosted on the same hosting provider (coming from the same C-level IP address). Google doesn't penalize sites like this, but other engines might. This is another situation where if it becomes apparent that you're doing it, you could get all your sites banned from search engines.