In a Class A network, what is the broadcast address?

• A. The address with all host bits on, e.g., 10.255.255.255
• B. The address with all network bits on
• C. The address 255.255.255.0
• D. The address 127.0.0.1

Answer: (A)

In IPv4, the broadcast address is the address within a subnet where all host bits are set to 1. For a Class A network, the default mask is 255.0.0.0, so the network portion is the first octet and the remaining 24 bits are hosts. The broadcast address is found by setting all those host bits to 1, giving an example like 10.255.255.255 for the 10.0.0.0/8 network. This address is used to reach all hosts in that subnet.

The other options don’t fit because 255.255.255.0 is a subnet mask, not a host address; 127.0.0.1 is the loopback address for the local host; and an address with all network bits on would specify the network part as all 1s, which does not represent the broadcast for a Class A subnet.