People hear all the time that if you want to create a large network of sites, it's important that they're hosted on separate Class C blocks. After reading some discussion in a service thread I realized that a lot of people have no idea what a Class C IP address actually is. So for those that don't already know, here is a layman's explanation of IP classes. IP addresses consist of 4 octets of numbers between 0 and 255. For Classes A, B and C each octet identifies the Network and Host (Node). Class A addresses have a first octet between 1 to 126 the first octet identifies the Net. the second, third, and fourth octets identify the Host (Node). NET.NODE.NODE.NODE Class A addresses are for large networks used by very large corporations, govt agencies, etc. Class B addresses have a first octet between 128 to 191 the first and second octets identifies the Net. the third and fourth octets identify the Host (Node). NET.NET.NODE.NODE Class B addresses are for mid-size networks used by large companies, city agencies, college campuses, etc. Class C addresses have a first octet between 192 to 223 the first, second, and third octets identifies the Net. the fourth octets identify the Host (Node). NET.NET.NET.NODE Class C addresses are for average networks used by small to mid-size companies or agencies. Class D addresses have a first octet between 224 to 239 Class E addresses have a first octet between 240 to 248 Class D and E addresses use the octets to identify groups rather than nodes and are used for different purposes than Class A through C networks. (the numbers in each range seem very random, but they're actually chosen because of the binary values of the numbers.) There are also some reserved addresses that are routed differently than regular addresses. Reserved addresses within the A, B and C classes: 10.0.0.0 to 10.255.255.255 private network 127.0.0.0 to 127.255.255.255 loopback address 169.254.0.0 to 169.254.255.255 private network 172.16.0.0 to 172.31.255.255 private network 192.168.0.0 to 192.168.255.255 private network Reserved addresses outside the classes are: 0.0.0.0 default route 255.255.255.255 host route So basically if you want to have Class C IP addresses then you need to be in the range between 192.0.0.0 to 220.127.116.11 excluding any reserved addresses. If only the numbers in the fourth octet change then you do have different Class C IP addresses, but they'll all be within the same Class C block. If you want to be on different Class C blocks then you need to get IP addresses that are different in the first 3 octets between 192.0.0.x and 223.255.255.x It really depends on what your doing with your sites whether you need to be on separate C blocks or not. If you have a fairly large network of sites and plan to do extensive backlinking between the sites then your probably better off to have the domains hosted on different Class C blocks. If you have a lot of sites but don't have an excessive amount of backlinking between the sites then just being hosted on different IPs within the same Class C block is possibly sufficient. If you just have a lot of sites that are unrelated and don't really do much backlinking then using a shared hosting account with a single IP is probably good enough. If you do feel you need to host your domains on different Class C blocks then hopefully this thread will help you out.