hardMultiple Choice
220-1201 Practice Question: A network administrator is designing a new subnet…
A network administrator is designing a new subnet scheme for a company with 4 departments: Sales (50 devices), HR (25 devices), IT (10 devices), and Management (5 devices). The company uses the 10.0.0.0/8 network. To minimize wasted IP addresses, which subnet mask should be used for the Sales department?
⚠ Common exam trap
The 220-1201 exam often tests the ability to calculate the smallest subnet that meets host requirements. The trap here is that candidates may choose a mask that is too small (e.g., a /27, which only provides 30 usable addresses, insufficient for 50 devices), or they may overestimate and pick a /24 mask out of habit, which works but wastes too many IP addresses.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
255.255.255.192
The Sales department requires 50 usable IP addresses. A /26 subnet mask (255.255.255.192) provides 64 total addresses, with 62 usable addresses (2^6 - 2 = 62), which is the smallest subnet that can accommodate 50 devices without wasting IPs. This aligns with the goal of minimizing wasted addresses in the 10.0.0.0/8 network.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
255.255.255.0
Why it's wrong here
This subnet mask, equivalent to a /24 CIDR prefix, dedicates the first three octets to the network portion, leaving the entire last octet (8 bits) for host addresses. This configuration provides 2^8 - 2, or 254 usable host IP addresses. While it certainly accommodates 50 devices, it results in substantial IP address waste and creates a larger broadcast domain than necessary, which can negatively impact network efficiency and security by allowing more broadcast traffic.
- ✓
255.255.255.192
Why this is correct
This subnet mask corresponds to a /26 CIDR prefix, meaning 26 bits are used for the network portion and 6 bits (32 - 26) are available for host addresses. This configuration yields 2^6 - 2, or 62 usable host IP addresses. This range is ideal for 50 devices, offering sufficient capacity with a reasonable buffer for minor expansion, thereby minimizing IP address waste and creating an appropriately sized broadcast domain for the specified requirement.
- ✗
255.255.255.224
Why it's wrong here
This subnet mask translates to a /27 CIDR prefix, which allocates 27 bits for the network and leaves 5 bits (32 - 27) for host addresses. Consequently, this configuration provides 2^5 - 2, or 30 usable host IP addresses. Given the requirement for 50 devices, this subnet mask is inadequate, as it cannot assign a unique IP address to every device, making it an unsuitable choice for the network design.
- ✗
255.255.255.240
Why it's wrong here
This subnet mask represents a /28 CIDR prefix, designating 28 bits for the network and only 4 bits (32 - 28) for host addresses. This severely limits the number of available hosts to 2^4 - 2, which is only 14 usable IP addresses. This capacity is significantly below the required 50 devices, rendering this subnet mask completely insufficient and impractical for the network administrator's design.
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Key term
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 220-1201 practice question is part of Courseiva's free CompTIA certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 220-1201 exam.