Link building is one of the most important aspects of search engine optimization. The more links a site has the better. Ethical link building takes time and unfortunately many have tire to find loopholes in the system. Some SEO specialists in the past have learned that they can cheat the system by building multiple websites and using them to link to the websites they want to place within search results. As a mechanism to defend against this search engines have updated their algorithms to check for duplicate C class IPs of inbound links. This article explains what C class IP addresses are, why you should avoid crossing links from duplicate C classes, and how to check the C class of inbound and outbound links.
An IP address is a unique number that identifies a computer on the internet. The four classes that make up an IP address are represented as AAA.BBB.CCC.DDD. Similar to computers your hosting account is assigned an IP address. Every domain hosted within the account will share the same IP address. As a result you should avoid cross linking any sites hosted within the same account. Even if the domains are registered under different names the fact that they share the same IP address tells search bots these sites are from the same neighbourhood. Sites that are linked like this look suspicious to search engines and the links will either be ignored or both sites can be penalized. If you have multiple sites and want to link them together you should assign the rel=”nofollow” attribute or host them on accounts with different class C IP addresses.
Even if you are the owner of a single site it is still important to avoid duplicate C class IPs of all inbound and outbound links. Each time you link to a site you will want to check its IP address to ensure the C class is different from yours. If your C class matches the person you are linking to and you link back it will look suspicious to search engines. It is also important to check the IPs of websites that link to you. For example, some directory owners have multiple websites hosted on the same account and you may not be aware of this. Submission to these directories can end up being a huge waste of time. Search engines know that these sites come from the same source and may only the links form one of these sites if any to count. Acquiring links from a variety of sources is important for optimization and the worst thing you want to do is taint your link portfolio by adding multiple links from duplicate C class IPs.
Fortunately checking for duplicate C class IPs address is easy if you have the right tool. The tool I like to use is called a class C IP checker and one can be found here at www.ip-report.com. This tool allows you to load a text file with all the IPs you wish to check. This feature saves you time as you continue to build your list of domains without having to rebuild the list from scratch.
Search engines have advanced their algorithms in order to prevent unethical link building practices. One precaution being taken is to check the C class of IPs to ensure that links are form different sources. All website owners should check the IPs of inbound and outbound links to in order to build a healthily link portfolio. Using a C class IP Checker is perhaps the easiest way to ensure all your links come form different sources.