↑ Classful addressing is obsolete and has not been used in the Internet since the implementation of Classless Inter-Domain Routing (CIDR), starting in 1993. For example, while Bản mẫu:IPaddr was a single class A network, it is common for organizations to divide it into smaller Bản mẫu:IPaddr or Bản mẫu:IPaddr networks. Contrary to a common misconception, a Bản mẫu:IPaddr subnet of a class A network is not referred to as a class B network. Likewise, a Bản mẫu:IPaddr subnet of a class A or B network is not referred to as a class C network. The class is determined by the first three bits of the prefix.[3]
