The Class C Checker tool allows you to check whether some
sites are hosted on the same Class C IP Range.
You might want to use the Class C Checker if you own several
cross-linked sites. If you do, it may be more efficient (for SEO
purposes) to host them on different Class C IP ranges.
Additionally, if you are going to get new links from different
sites, you may want to see whether they share the same Class C
IP range. Again, this could make a difference for SEO purposes.