The answer is 254 usable hosts. A subnet mask of 255.255.255.0, also written as /24, creates a single network with 256 total IP addresses, but the very first address is reserved as the network ID and the very last as the broadcast address, leaving 254 addresses available for devices like computers, printers, and phones. On the CompTIA A+ Core 1 220-1201 exam, this concept tests your understanding of IPv4 subnetting fundamentals and is often paired with a scenario asking whether a given subnet can support a specific number of devices—a common trap is forgetting to subtract the two reserved addresses and mistakenly answering 256. For a quick memory tip, remember the “minus two” rule: for any subnet, total addresses minus two equals usable hosts, and with a /24, think “256 minus 2 leaves 254.”
220-1201 Network Configuration Concepts Practice Question
This 220-1201 practice question tests your understanding of network configuration concepts. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A technician is setting up a new office network with 50 devices. The network must support growth up to 100 devices. The technician chooses a subnet mask of 255.255.255.0. How many usable host addresses does this subnet provide?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
254
A subnet mask of 255.255.255.0 (or /24) provides 256 total addresses, with 254 usable for hosts (the first address is the network ID and the last is the broadcast address). This is sufficient for the current 50 devices and allows for growth up to 100, but not beyond 254.
Key principle: Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
254
Why this is correct
With a /24 subnet, there are 256 addresses total, minus 2 for network and broadcast, leaving 254 usable host addresses.
255 is incorrect because one address is reserved for the network ID and one for broadcast, so usable is 254.
✗
256
Why it's wrong here
256 is the total number of addresses, but two are reserved, so usable is 254.
✗
128
Why it's wrong here
128 would be the usable hosts for a /25 subnet (255.255.255.128), not a /24.
Common exam traps
Common exam trap: usable hosts are not the same as total addresses
Subnetting questions often tempt you into counting all addresses. In normal IPv4 subnets, the network and broadcast addresses are not usable host addresses.
Detailed technical explanation
How to think about this question
Subnetting questions test whether you can identify the network, broadcast address, usable range, mask and correct subnet. Slow down enough to calculate the block size correctly.
KKey Concepts to Remember
CIDR notation defines the prefix length.
Block size helps identify subnet boundaries.
Network and broadcast addresses are not usable hosts in normal IPv4 subnets.
The required host count determines the smallest suitable subnet.
TExam Day Tips
→Write the block size before choosing the subnet.
→Check whether the question asks for hosts, subnets or a specific address range.
→Do not confuse /24, /25, /26 and /27 host counts.
Key takeaway
Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
Real-world example
How this comes up in practice
A network engineer segments a warehouse floor into three subnets: 20 scanners, 5 printers, and 2 management hosts. Picking the wrong mask wastes addresses or leaves too few usable hosts. Exam questions test whether you can apply CIDR notation, calculate block size, and identify the correct usable-host range for a given prefix.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this 220-1201 question in full detail.
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related 220-1201 subnetting questions on CIDR, address ranges, and subnet selection.
Network Configuration Concepts — This question tests Network Configuration Concepts — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: 254 — A subnet mask of 255.255.255.0 (or /24) provides 256 total addresses, with 254 usable for hosts (the first address is the network ID and the last is the broadcast address). This is sufficient for the current 50 devices and allows for growth up to 100, but not beyond 254.
What should I do if I get this 220-1201 question wrong?
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related 220-1201 subnetting questions on CIDR, address ranges, and subnet selection.
What is the key concept behind this question?
CIDR notation defines the prefix length.
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Question Discussion
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