basically it's supposed to be no good for seo having many or all links form the same IP or same IP block, same C class IP would be if the first 3 octets of the IP are same like so 111.222.333.123 111.222.333.987 you might find this tool helpful http://www.ip-report.com/
There is no problem with getting links from multiple sites on the same class C IP block if they are legitimate. This happens all the time naturally in the wild. MOST websites on the internet are using shared hosting. ISPs like Godaddy will have multiple shared servers running from different IPs in the the same class C IP block... each server with hundreds of domains. Only a small percentage of the sites on the web have dedicated IP addresses, so it is quite natural for a site to have some links from multiple domains at a single class C IP block. However, if you are participating in a link farm of hundreds of sites that are all interlinked and all hosted on the same IP or same class C IP block, this makes it much easier for Google to detect your link farm.