Firms with multiple sites must proceed with care. At a bare minimum, any additional sites should be hosted by different hosting providers or at least reside on disparate Class C networks. Many SEO firms ignore this point – we have seen many cases where firms have multiple ‘front doors’ with too-similar content hosted on the same IP address. While some search engines apparently do not penalize this network configuration, this is far from certain and SEO firms that implement this practice are sharing huge risks with their clients.

Impact

Disparate Class C networks may be hosted by the same network provider, so the gains from this technique may be small. However, Class C networks of course may be hosted by different providers, implying a greater degree of independence and wider deployments. Few network hosts offer Class C networks on the same server, so multiple Class C’s seem to imply that sites are deployed across multiple servers.

Abuse

Some network hosts go the other way and specialize in servers with many (even hundreds of) Class C network addresses on the same machine. This practice has brought the ire of many, as this practice accelerated the consumption of the last few Type IV IP addresses, which has now officially run out.

Conclusion

In summary, while it is unknown what penalty, if any, if incurred by firms deploying multiple similar sites on the same Class C network, it is probably for the best for a company not to take chances. The main factor is the similarity of content (which should be kept to almost zero), but deploying on multiple Class C networks is probably a wise precaution.