IP addresses that use a default subnet mask per class are described by which addressing method?

• A. Classful
• B. Classless Inter-Domain Routing (CIDR)
• C. Dynamic Host Configuration Protocol
• D. Private Internet Protocol (Private IP)

Answer: (A)

Classful addressing uses fixed default subnet masks that are tied to the IP address class. In this approach, the first octet of the address determines whether it’s Class A, B, or C, and the default masks are /8, /16, and /24 respectively. So, when an address is described using its default mask for its class, it’s being described by classful addressing. CIDR is the modern, classless alternative that allows arbitrary prefix lengths (like /19 or /22) and isn’t bound to the class-based defaults. DHCP is just the protocol for dynamically assigning addresses, and Private IP refers to reserved address ranges, not the addressing method itself.