Using VLSM on a 192.168.0.0/24 network, you need subnets for 50 hosts, 20 hosts, and 6 hosts. Which set of masks fits while minimizing waste?

Using VLSM on a 192.168.0.0/24 network, you need subnets for 50 hosts, 20 hosts, and 6 hosts. Which set of masks fits while minimizing waste?

• A. 50 hosts -> /26, 20 hosts -> /27, 6 hosts -> /29
• B. 50 hosts -> /25, 20 hosts -> /28, 6 hosts -> /30
• C. 50 hosts -> /27, 20 hosts -> /26, 6 hosts -> /29
• D. 50 hosts -> /26, 20 hosts -> /30, 6 hosts -> /28

Answer: (A)

In VLSM you size each subnet to the exact number of hosts needed, using the smallest mask that still fits. For 50 hosts you need at least 50 usable addresses, and a /26 provides 64 addresses total (62 usable), which comfortably covers 50. A smaller mask like /27 would only yield 30 usable addresses, which isn’t enough. For 20 hosts a /27 gives 32 total addresses (30 usable), enough for 20, while a /28 would provide only 14 usable and would be insufficient. For 6 hosts a /29 provides 8 total addresses (6 usable), exactly matching the requirement, whereas a /30 would give only 2 usable. So the most efficient arrangement is to assign 192.168.0.0/26 for the 50-host subnet, 192.168.0.64/27 for the 20-host subnet, and 192.168.0.96/29 for the 6-host subnet. This order (largest first) minimizes waste within the 192.168.0.0/24, leaving some addresses unused at the end but avoiding oversized subnets.

In VLSM you size each subnet to the exact number of hosts needed, using the smallest mask that still fits. For 50 hosts you need at least 50 usable addresses, and a /26 provides 64 addresses total (62 usable), which comfortably covers 50. A smaller mask like /27 would only yield 30 usable addresses, which isn’t enough. For 20 hosts a /27 gives 32 total addresses (30 usable), enough for 20, while a /28 would provide only 14 usable and would be insufficient. For 6 hosts a /29 provides 8 total addresses (6 usable), exactly matching the requirement, whereas a /30 would give only 2 usable.

So the most efficient arrangement is to assign 192.168.0.0/26 for the 50-host subnet, 192.168.0.64/27 for the 20-host subnet, and 192.168.0.96/29 for the 6-host subnet. This order (largest first) minimizes waste within the 192.168.0.0/24, leaving some addresses unused at the end but avoiding oversized subnets.