In classful IPv4 addressing, which class has 16,384 networks?

• A. Class B
• B. Class A
• C. Class C
• D. Class D

Answer: (A)

In classful IPv4 addressing, how many networks exist in each class depends on how many bits are allotted to the network portion. For Class B, the first two bits are fixed as 10, which leaves 14 bits for the network number across the first two octets. 2^14 equals 16,384, so there are 16,384 possible networks in this class. By comparison, Class A fixes the first bit as 0, leaving 7 bits for the network (about 128 networks, with some reserved), and Class C fixes the first three bits as 110, leaving 21 bits for the network (about 2,097,152 networks). Class D is used for multicast, so its addressing concept differs.