What does "C IP" mean?
C IP means C class IP. It is the third number in an IP address (which is basically the address of your computer or server on the internet).
When two websites have the same C IP, it suggests that they are on the same host.
Why does this matter?
Here are two examples of how C IP can matter:
First, if you own two websites with the same C IP and they are linking to each other, then Google sees this as an indication that they might be owned by the same person. This might lead to less link juice, or even a penalty.
Second, you might notice that a lot of links are coming to your site from websites with the same C IP. This could indicate a coordinated effort by an individual to send you a lot of links (often quite spammy ones), which could hurt your site ranking. In that case, you should carefully analyze those links and consider disavowing them to combat negative SEO.