102-500 · Question #67
How many IP addresses can be used for unique hosts inside the IPv4 subnet 192.168.2.128/26?
The correct answer is D. 62. A /26 prefix leaves 6 host bits (32 − 26 = 6), giving 2⁶ = 64 total addresses. Subtract 1 for the network address (192.168.2.128) and 1 for the broadcast address (192.168.2.191), leaving 62 usable host addresses - making D correct. The distractors each correspond to a different…
Question
Options
- A6
- B14
- C30
- D62
- E126
How the community answered
(24 responses)- A4% (1)
- C4% (1)
- D83% (20)
- E8% (2)
Explanation
A /26 prefix leaves 6 host bits (32 − 26 = 6), giving 2⁶ = 64 total addresses. Subtract 1 for the network address (192.168.2.128) and 1 for the broadcast address (192.168.2.191), leaving 62 usable host addresses - making D correct.
The distractors each correspond to a different prefix length: 62 (D) is /26, 30 (C) is /27 (5 host bits), 14 (B) is /28 (4 host bits), 6 (A) is /29 (3 host bits), and 126 (E) is /25 (7 host bits) - each wrong answer is simply the result of miscounting the host bits by ±1.
Memory tip: Use the formula 2^(32 − prefix) − 2. For /26: 2^6 − 2 = 62. Every time the prefix increases by 1, the host count roughly halves; decreasing by 1 roughly doubles it.
Topics
Community Discussion
No community discussion yet for this question.