The correct choice is 192.168.1.0/24 because it provides 254 usable private IP addresses, which comfortably supports 30 devices while leaving room for growth, and it falls within the 192.168.0.0/16 private range defined by RFC 1918. The /24 subnet mask is ideal for small office networks like this one, as it offers a simple, standard configuration that avoids the waste of larger ranges like 10.0.0.0/8. On the CompTIA A+ Core 1 220-1201 exam, this question tests your ability to match subnet size to device count and to distinguish private IP ranges from the public /28 block used for the WAN interface—a common trap is confusing the ISP’s public subnet with the internal private network. Remember that 192.168.x.x is the go-to for home and small office LANs, while 10.x.x.x is reserved for larger enterprise networks. A handy memory tip: “192 starts small, 10 is for the big show.”
220-1101 IP Addressing Practice Question
This 220-1201 practice question tests your understanding of ip addressing. 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 branch office and needs to assign IPs to 30 devices. The ISP provided a public IP block of 203.0.113.0/28. The technician decides to use private IPs internally and NAT. Which of the following is the most appropriate private IP range for this network?
Why wrong: These are public IPs from the ISP's block, not private IPs; they should be used for the router's WAN interface, not internal devices.
B
10.0.0.0/8
Why wrong: 10.0.0.0/8 is a private range but is far too large for 30 devices; it would work but is not the most appropriate choice for a small office.
C
192.168.1.0/24
192.168.1.0/24 is a private range that provides 254 usable addresses, ideal for a small office with 30 devices.
D
172.16.0.0/12
Why wrong: 172.16.0.0/12 is a private range but is typically used for larger networks; it is less common for small offices and is not the most appropriate.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
192.168.1.0/24
For a small network with 30 devices, a /24 subnet (e.g., 192.168.1.0/24) provides 254 usable addresses, which is sufficient. The /28 public block is for the WAN interface. This tests knowledge of private IP ranges (10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16) and subnet sizing.
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.
✗
203.0.113.1 to 203.0.113.14
Why it's wrong here
These are public IPs from the ISP's block, not private IPs; they should be used for the router's WAN interface, not internal devices.
✗
10.0.0.0/8
Why it's wrong here
10.0.0.0/8 is a private range but is far too large for 30 devices; it would work but is not the most appropriate choice for a small office.
✓
192.168.1.0/24
Why this is correct
192.168.1.0/24 is a private range that provides 254 usable addresses, ideal for a small office with 30 devices.
172.16.0.0/12 is a private range but is typically used for larger networks; it is less common for small offices and is not the most appropriate.
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 small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
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.
IP Addressing — This question tests IP Addressing — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: 192.168.1.0/24 — For a small network with 30 devices, a /24 subnet (e.g., 192.168.1.0/24) provides 254 usable addresses, which is sufficient. The /28 public block is for the WAN interface. This tests knowledge of private IP ranges (10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16) and subnet sizing.
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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