200-901 Network Fundamentals Practice Question
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.)
⚠ Common exam trap
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.
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.
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.
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.
- ✓
The broadcast address is 172.16.5.127.
Why this is correct
Broadcast is the last address in the subnet: 172.16.5.127.
- ✓
The subnet mask is 255.255.255.128.
Why this is correct
/25 corresponds to mask 255.255.255.128.
- ✗
The network address is 172.16.5.128.
Why it's wrong here
The network address is 172.16.5.0, not .128.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.