An IP address is divided in to four parts (A, B, C and D). Class A is intended for relatively small number of networks that had a large number of hosts attached. Class B is intended for some networks that had an intermediate number of hosts involved where as Class C is planned for a large number of networks that would have a small number of hosts involved.
Starting address for A block is 0.0.0.0 where as the end address for the same is 127.255.255.255. For B block its range is from 128.0.0.0 to 191.255.255.255. C block ranges from 192.0.0.0 to 223.255.255.255 where as D blog ranges from 224.0.0.0 to 239.255.255.255.
Web-host are given a separate Class”C” which means if having two different C block, then it is two different web-host. But if two different web-host has same C block that means they are from the same area and if having the same link in their web pages their link value gets decreased.
For Example if someone is making a link for “SEO Dublin” and its competitor is working on the same link. If they belong to the nearby location then their C Class IP is assumed to be same by Google. This will affect the link “SEO Dublin” of both the webhost and their link value for “SEO Dublin” will get decreased. Same Class C Block IP
Host1 = 191.167.221.225
Host2 = 191.167.221.110
The above example is of two different web-host having same C Block IP. So it must be take care of C Class IP in SEO too as it is very important aspect of link building.