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220-1201 Practice Question: A technician is configuring a small branch office…
A technician is configuring a small branch office network with 30 devices. The network uses a single router with DHCP enabled. To conserve IP addresses, the technician decides to use a subnet that provides exactly enough usable addresses for the devices, with minimal waste. Which subnet mask should the technician choose?
⚠ Common exam trap
CompTIA A+ often tests the concept that the subnet mask must provide at least the required number of usable hosts, but candidates mistakenly choose a mask that gives exactly the total addresses (e.g., 32) without subtracting the network and broadcast addresses, or they pick a larger subnet (like /26) thinking it is safer, ignoring the 'minimal waste' constraint.
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
✓
255.255.255.224
The network requires exactly 30 usable IP addresses. A /27 subnet (mask 255.255.255.224) provides 32 total addresses, with 30 usable (2^5 - 2 = 30), matching the requirement with minimal waste. This is the most efficient choice because it supplies the exact number of hosts needed without leaving a large pool of unused addresses.
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
Incorrect. A /24 provides 254 usable addresses, which is far more than needed and wastes addresses.
- ✓
255.255.255.224
Why this is correct
Correct. A /27 provides 30 usable addresses, exactly enough for 30 devices with minimal waste.
- ✗
255.255.255.240
Why it's wrong here
Incorrect. A /28 provides only 14 usable addresses, which is insufficient for 30 devices.
- ✗
255.255.255.192
Why it's wrong here
Incorrect. A /26 provides 62 usable addresses, which is more than needed but not the most efficient choice.
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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.