Which subnetting technique allows variable-length masks to optimize IP address allocation?

• A. Variable Length Subnet Masking (VLSM)
• B. CIDR
• C. Subnetting
• D. Subnet Aggregation

Answer: (A)

Allocating IP addresses efficiently by tailoring subnet sizes to each subnet’s needs. Variable-length subnet masks let you assign different prefix lengths to different subnets within the same major network, so a small branch can use a long mask with few hosts while a larger department uses a shorter mask with more hosts. This approach minimizes wasted addresses and makes the most of the available address space. The technique that provides this capability is Variable Length Subnet Masking. In contrast, traditional subnetting often uses the same mask across all subnets, and while CIDR allows variable-length prefixes in routing, the practical subnetting practice to optimize a local address space is VLSM. Subnet Aggregation is about combining routes for summary tables, not about varying mask lengths.