In case of class A and B IP addresses, each of them provides for a large number of hosts. For class A, the total numbers of hosts available are 224-2 or 16,777,216 hosts (class A has 24 bits available for host component and each bit can have two values – 0 and 1. Out of the total value one address is for network address and the other for broadcast. So two addresses are deducted). Similarly a Class B addresses provides for 216-2 or 65,534 hosts. In the first chapter you learned about disadvantages of large networks and why it becomes necessary to divide them into smaller networks joined by routers. So creating a network with total number of hosts allowed for class A or B addresses will cause a lot of problems. Meanwhile creating small networks with class A or B addresses will waste a lot of addresses.