What is the network address for a Class A network?

• A. 10.0.0.0
• B. 0.0.0.0
• C. 255.0.0.0
• D. 192.168.0.0

Answer: (A)

In IPv4, a Class A network uses the default mask 255.0.0.0, so the network address is the first octet plus three zeros. That means the network address takes the form N.0.0.0, where N is 1 through 126 (127 is reserved for loopback). A common example is 10.0.0.0, which represents a Class A network because 10 falls in the Class A range and the host portion is all zeros.

The other addresses aren’t Class A network addresses under the traditional classful rules: 0.0.0.0 is the unspecified address and not a valid network identifier; 255.0.0.0 is a subnet mask, not an address; 192.168.0.0 is a network address for a Class C private network, not Class A.