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200-901 Practice Question: Needs to create a new subnet that can support at…
A network engineer needs to create a new subnet that can support at least 50 usable host addresses for a development environment. Which TWO subnet masks would meet this requirement? (Choose two.)
⚠ Common exam trap
Cisco often tests the distinction between 'total addresses' and 'usable host addresses' — candidates mistakenly count the network and broadcast addresses as usable, leading them to select a mask like /27 (32 total addresses) thinking it supports 32 hosts instead of the actual 30.
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
✓
255.255.255.128 (/25)
(255.255.255.128 /25) provides 126 usable host addresses (2^(32-25) - 2 = 126), which exceeds the requirement of 50. Option C (255.255.255.192 /26) provides 62 usable host addresses (2^(32-26) - 2 = 62), also meeting the requirement. Both masks are valid because they yield at least 50 usable IPs for the development subnet.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
255.255.255.224 (/27)
Why it's wrong here
Incorrect. /27 provides only 30 usable host addresses, which is insufficient for 50 hosts.
- ✓
255.255.255.128 (/25)
Why this is correct
Correct. /25 provides 2^(32-25)-2 = 126 usable host addresses, which is more than 50.
- ✓
255.255.255.192 (/26)
Why this is correct
Correct. /26 provides 2^(32-26)-2 = 62 usable host addresses, which is more than 50.
- ✗
255.255.255.248 (/29)
Why it's wrong here
Incorrect. /29 provides only 6 usable host addresses, insufficient.
- ✗
255.255.255.240 (/28)
Why it's wrong here
Incorrect. /28 provides only 14 usable host addresses, far below the requirement.
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JA
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.