Which of the following represents a classless addressing scheme?

• A. CIDR Notation
• B. Classful Addressing
• C. Static IP
• D. DHCP

Answer: (A)

Classless addressing uses a prefix length to determine the network portion of an address, rather than fixed class-based masks. This is implemented with CIDR notation, which writes an IP address followed by a slash and a number indicating how many bits are used for the network part, for example 192.168.1.0/24. This approach allows variable-length subnet masks (VLSM) and enables route aggregation, making efficient use of address space and keeping routing tables manageable.

In contrast, the old classful scheme fixed the subnet mask based on the first octet (A, B, or C classes), which often wasted addresses and made route summarization harder. Static IP and DHCP are methods for assigning addresses to hosts, but they don’t define how networks are addressed themselves; CIDR notation is what expresses the classless addressing scheme.