But are you wasting your time? Links from sites with the same IP C-block are downgraded by the search engines because these links are less likely to be content-related links and more likely to be links purely for SEO purposes.
What’s a C-Block Address
IP addresses are the internet’s equivalent of zip codes. For our purposes, we can think of an IP address as being in the format AAA.BBB.CCC.DDD. For example, 192.168.222.001. Web sites hosted with the same host will normally have the same C-block – ie the first 9 numbers will be the same: 192.168.222.
That’s pretty much all we need to be concerned about in this context. What it means is that when you link together two of your sites that have the same C-block, Google will downgrade the importance of the link.
Which means that linking between your own sites on the same web host is of little value. If your sites have low Page Rank this may not be too much of an issue. However, if you have high ranking sites, what a waste.
Unfortunately, it doesn’t stop there. If you link too much between your sites on the same C-block, you may be penalised as a spammer. But it gets worse. If you are on the same C-block as a nasty spammer, the entire C-block may be penalised.
So what can you do?
Spread your sites around good quality hosts! Remember that many resellers may be selling you space on the same C-block as your other sites.