What is the primary purpose of VLSM in IPv4 subnetting?

• A. It allows more efficient use of address space by creating subnets of different sizes
• B. It simplifies routing by using a single mask
• C. It increases broadcast domains
• D. It prevents subnetting

Answer: (A)

Variable Length Subnet Masking lets you tailor subnet sizes to fit the needs of each segment, so IPv4 address space is used more efficiently. With VLSM you can split a network into subnets that have different numbers of host addresses—for example one subnet for 50 hosts, another for 14, and another for 200—while still living under the same major network address. This flexibility avoids wasting addresses that would occur if every subnet had to be the same size.

This is not about using a single mask across the network, which would force every subnet to be the same size and waste space. It also isn’t about increasing broadcast domains as an explicit goal of VLSM; subnetting changes the number of broadcast domains based on how many subnets you create, but the primary benefit of VLSM is more efficient address usage. And it doesn’t prevent subnetting; it enables more granular subnetting.