What is the maximum usable Class A network addresses after reservations?

• A. 126 usable Class A network addresses.
• B. 128 usable Class A network addresses.
• C. 16384 usable Class A network addresses.
• D. 254 usable Class A network addresses.

Answer: (A)

Understanding Class A addressing helps here: Class A uses the first octet to identify the network, and valid network values range from 1 to 126. Values 0 and 127 are reserved (0 for special purposes like "this network" and 127 for loopback). So, after reservations, there are 126 usable Class A network numbers.

The other numbers describe host counts per network or networks in other classes, not the count of Class A networks: for example, 254 is the usable hosts in a Class C network, and 16384 relates to the number of Class B networks, not Class A networks.