Which subnet best supports 15 printers on a LAN?
Short answer
A 10.1.15.0/27
Question
Key Takeaways
This question tests the difference between total IP addresses and usable host addresses — a /28 gives 16 total addresses but only 14 usable, which is one short of 15 printers.
For 15 network printers, you need a subnet with at least 15 usable host addresses. The /27 subnet provides 30 usable hosts, making it the only correct choice among /27, /30, /28, and /29.
Common mistake: Choosing C (/28) because 2^4 = 16 appears sufficient; however, this ignores that the network and broadcast addresses are not usable, leaving only 14 hosts.
Expert Analysis
Why the Answer Is Correct
Option A, 10.1.15.0/27, uses a mask of 255.255.255.224. The host bits are 5, so the subnet gives 2^5 = 32 total addresses, of which 32 - 2 = 30 are usable for hosts. Since 30 ≥ 15, this easily supports all 15 printers and leaves room for growth.
Why the Other Options Are Wrong
Option B (/30) provides only 2 usable hosts, and Option D (/29) provides only 6, both obviously insufficient. Option C (/28) provides 2^4 = 16 total addresses, but after subtracting the network address and broadcast address, only 14 are usable — exactly one fewer than required for 15 printers.
Community Comment Notes
The most-upvoted comments correctly explain the /27 calculation, noting that 2^5 = 32 and subtracting 2 gives 30 usable hosts. One comment incorrectly chose /28, saying it gives 16 host addresses, but this is the classic trap: a /28 subnet has 16 IP addresses total, not 16 usable host addresses. The vote distribution (92 for A) confirms the correct consensus.
Official Reference
These links open the official vendor documentation in a new tab.
Exam Strategy
On subnetting questions, always calculate usable addresses using 2^(32 - mask) - 2 and compare the result to the device count. Watch for options like /28 that appear close but fail because the network and broadcast addresses take away two usable addresses.
Community Votes
100% of anonymous learners picked answer A. Votes are pick records left by other test-takers — they are not the verified answer.
Discussion 5 contributions
Compiled from public community threads and reader submissions, lightly edited for clarity. Handles and vote tallies are shown as recorded, and comments reflect the views of individual contributors.
From public community threads 5
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IT1992 👍 9GUYS WEVE GOT 15 PRINTERS SO 10.1.15.0/27 IS THE CORRECT ANSWER COZ 2^5=32 32-2 FOR NETWORK ID AN BROADCAST ITS GONNA BE 30 HOST EVEN IF IT IS MORE THAN ENOUGH BUT THAT THE ANSWER /28 IT WILL GIVE YOU 16-2 = 14 WE NOW SHOT WITH 1 HOST SO A IS THE ANSWER FELLAS
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TheGuy1212 👍 2To support 15 network printers, you need a subnet with enough host addresses. The number of available host addresses in each subnet is given by 2^(32 - subnet mask). Let's evaluate the options: A. 10.1.15.0/27 - 2^(32-27) = 2^5 = 32 host addresses (more than needed) B. 10.8.4.0/30 - 2^(32-30) = 2^2 = 4 host addresses (not enough) C. 10.10.8.0/28 - 2^(32-28) = 2^4 = 16 host addresses (sufficient) D. 10.15.1.0/29 - 2^(32-29) = 2^3 = 8 host addresses (not enough) Therefore, option C (10.10.8.0/28) is the best choice as it provides enough host addresses to support the 15 network printers while minimizing address wastage.
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Bunaventi 👍 1 Answered Cid say C)/28. /28 gives you 16 host addresses which is enough for 15 printers.
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Sgthud 👍 7 Answered A/27 gives you 32-2 = 30 hosts
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subaie503 👍 4 Answered AA. 10.1.15.0/27
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