We are a specialty web design and host company and we run a few dozen websites on the same IIS server, including our own corporate website. All our clients' websites have a link that points to our corporate website (anchor link: "site design by xxxxx"). Now some of these websites have a PR of 1, 2 and even 4. Questions: 1. Will Google and other search engines discount the value of those links because they are on the same server? 2. What if we assigned unique IP addresses (our host offers us this option) to each of those websites? Will the search engines still know that it is the same server (from say, MAC address, or through other means)? Any thoughts and comments appreciated.
Yes, links backlinks form the same server will be discounted, and sometimes even ignored. Yes, having unique IPs will help, but they'd really need to be on different class Cs to do much good. And even then, there's a good chance the links would still be discounted.
It is always better to get backlinks from different C-class IPs. If all the sites linking back to you are from the same server as the page's host is in, then its value may be discounted and ignored.