- A
The subnet mask is 255.255.255.192.
Why wrong: 255.255.255.192 is /26.
- B
There are 126 usable host addresses.
2^(32-25) - 2 = 126.
- C
The broadcast address is 172.16.5.127.
Broadcast is the last address in the subnet: 172.16.5.127.
- D
The subnet mask is 255.255.255.128.
/25 corresponds to mask 255.255.255.128.
- E
The network address is 172.16.5.128.
Why wrong: The network address is 172.16.5.0, not .128.
Question 566 of 1,000
200-901 Network Fundamentals Practice Question
This 200-901 practice question tests your understanding of network fundamentals. 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.
An engineer is configuring a new IPv4 subnet with the address 172.16.5.0/25. Which three statements are true about this subnet? (Choose three.)
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
✓
There are 126 usable host addresses.
Option B is correct because a /25 prefix length corresponds to a subnet mask of 255.255.255.128, which provides 2^(32-25) - 2 = 128 - 2 = 126 usable host addresses. The network address is 172.16.5.0, and the broadcast address is 172.16.5.127, leaving addresses 172.16.5.1 through 172.16.5.126 for hosts.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
The subnet mask is 255.255.255.192.
Why it's wrong here
255.255.255.192 is /26.
- ✓
There are 126 usable host addresses.
Why this is correct
2^(32-25) - 2 = 126.
Related concept
Read the scenario before looking for a memorised answer.
- ✓
The broadcast address is 172.16.5.127.
Why this is correct
Broadcast is the last address in the subnet: 172.16.5.127.
Related concept
Read the scenario before looking for a memorised answer.
- ✓
The subnet mask is 255.255.255.128.
Why this is correct
/25 corresponds to mask 255.255.255.128.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
The network address is 172.16.5.128.
Why it's wrong here
The network address is 172.16.5.0, not .128.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the confusion between the network address and the first usable host address, or the tendency to misapply the subnet mask by using 255.255.255.192 (/26) instead of 255.255.255.128 (/25) when the prefix length is given.
Detailed technical explanation
How to think about this question
In IPv4 subnetting, the /25 prefix uses the first 25 bits for the network portion, leaving 7 bits for hosts. The subnet mask 255.255.255.128 in binary is 11111111.11111111.11111111.10000000. The broadcast address is calculated by setting all host bits to 1, so for 172.16.5.0/25, the last octet in binary is 00000000, and setting the 7 host bits to 1 yields 01111111, which is 127. This subnetting is commonly used in enterprise networks to create two equal-sized subnets from a /24 block, such as for separating management and production traffic.
KKey Concepts to Remember
- Read the scenario before looking for a memorised answer.
- Find the constraint that changes the correct option.
- Eliminate answers that are true in general but not in this case.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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.
Visual reference
What to study next
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FAQ
Questions learners often ask
What does this 200-901 question test?
Network Fundamentals — This question tests Network Fundamentals — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: There are 126 usable host addresses. — Option B is correct because a /25 prefix length corresponds to a subnet mask of 255.255.255.128, which provides 2^(32-25) - 2 = 128 - 2 = 126 usable host addresses. The network address is 172.16.5.0, and the broadcast address is 172.16.5.127, leaving addresses 172.16.5.1 through 172.16.5.126 for hosts.
What should I do if I get this 200-901 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jul 4, 2026
This 200-901 practice question is part of Courseiva's free Cisco 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 200-901 exam.
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