200-901 Network Fundamentals Practice Question
A network administrator needs to assign IP addresses to devices on a subnet with a /25 prefix. How many usable host addresses are available?
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
✓
126
A /25 subnet has 7 bits for hosts (32-25=7), giving 2^7 = 128 total addresses, minus 2 (network and broadcast) = 126 usable 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.
- ✗
254
Why it's wrong here
254 is for a /24 subnet.
- ✓
126
Why this is correct
2^(32-25) - 2 = 128 - 2 = 126.
- ✗
64
Why it's wrong here
64 is for a /26 subnet.
- ✗
128
Why it's wrong here
128 is the total number of addresses including network and broadcast.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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