When you have multiple subnet masks on one network, what is this practice called?

• A. Variable Length Subnet Mask
• B. Subnet Masking
• C. Classful Subnetting
• D. Subnetting

Answer: (A)

Varying the subnet size within the same network is called Variable Length Subnet Masking. It lets you assign different subnet masks to different parts of a network, matching each segment’s needs. Instead of sticking to one fixed mask for all subnets (like in older classful subnetting), you can use masks of different lengths—such as /26 for a subnet with about 62 usable hosts, /27 for around 30, and /29 for about 6—within the same larger network. This makes more efficient use of IP addresses by avoiding waste. This approach relies on classless routing (CIDR), which supports multiple masks within one network. In contrast, traditional subnetting or classful subnetting uses a single mask for all subnets, which is less flexible.