olemus
IP-adresseerimise süsteem protokollis IPv4, jaotab Interneti aadressiruumi viieks klassiks; võrguosa v määrab ülemaailmne organ, hostiosa h määrab kohalik organ
= a network addressing architecture used in the Internet from 1981 until 1993, divides the IP address space for Internet Protocol version 4 (IPv4) into five address classes based on the leading four address bits

klassid
A - maks. 128 võrku, igas kuni 16777216 aadressi
(0vvvvvvv.hhhhhhhh.hhhhhhhh.hhhhhhhh)
B - 16384 võrku, igas kuni 65535 aadressi
(10vvvvvv.vvvvvvvv.hhhhhhhh.hhhhhhhh)
C - 2097152 võrku, igas kuni 254 aadressi + 2 eriaadressi
(110vvvvv.vvvvvvvv.vvvvvvvv.hhhhhhhh)
D - multisaade
E - reserv

ülevaateid
https://en.wikipedia.org/wiki/Classful_network
http://www.freesoft.org/CIE/Course/Subnet/202.htm
http://www.tcpipguide.com/free/t_IPClassfulAddressingOverviewandAddressClasses.htm
https://users.cs.jmu.edu/aboutams/Web/Networking/Spring03/Lectures/Lecture%203-%20IP%20Classful%20Addressing.pdf

vt ka
- CIDR