¹¹. For example, a so-called Class C IP address block is the smallest contiguous block assignment which can be made to an organization. The Class C block defines a three-byte netid and a single-byte hostid, enough for 255 hosts. (All zeros in the hostid field means the network address rather than a host address). If a network administrator only had a dozen hosts to actually assign addresses to, they would only use 12 out of the 255 host addresses available to them. This is not an uncommon situation.