Class B Address. An IP address which belongs to class B has the first two bits in the first octet set to 10, i.e. Class B IP Addresses range from 128.0.x.x to 191.255.x.x.lass C Address. The first octet of Class C IP address has its first 3 bits set to 110, that is: Class C IP addresses range from 192.0.0.x to 223.255.255.x. The default subnet mask for Class C is 255.255.255.x.