CCNA /28 subnet mask equals 255.255.255.240 Practice Question
A host address is 10.77.4.141/28. Which address is the network address of the subnet?
⚠ Common exam trap
Be careful not to confuse host addresses with network addresses. Always calculate the subnet block to find the network address.
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
✓
10.77.4.128
A /28 subnet has a block size of 16. In practical terms, the last-octet blocks are 0-15, 16-31, 32-47, and so on. Because 141 falls within the 128-143 block, the network address is 10.77.4.128. This is a clean addressing-boundary question that rewards careful block calculation rather than guesswork.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
10.77.4.128
Why this is correct
The host address 10.77.4.141 falls within the /28 subnet that starts at 10.77.4.128, because the /28 block size is 16 addresses (128-143). The network address is the first address of that block, where all host bits are zero, so 10.77.4.128 is the correct network address. Any address in the range 10.77.4.129 through 10.77.4.142 is valid for hosts, while .143 is the broadcast.
- ✗
10.77.4.143
Why it's wrong here
10.77.4.143 is actually the broadcast address for the 10.77.4.128/28 subnet, not the network address. In a /28 network, the broadcast is the last address in the block, calculated as the network address plus the block size minus one (128 + 16 - 1 = 143). Since the question asks for the network address, which is the first address in the subnet, this option is incorrect.
When this WOULD be correct
In a different question where the task is to identify the last usable host address in the subnet, 10.77.4.143 would be correct, as it is the highest address before the broadcast address of 10.77.4.143 in a /28 subnet.
- ✗
10.77.4.144
Why it's wrong here
10.77.4.144 is the network address for the next /28 subnet (10.77.4.144/28), which spans addresses 144-159. The host 10.77.4.141 is numerically less than 144, so it cannot belong to this later subnet. Choosing this option would place the host in the wrong network block, making it invalid for identifying the subnet that contains .141.
When this WOULD be correct
If the question asked for the first usable host address in the subnet instead of the network address, then 10.77.4.144 could be considered correct, as it is the first address after the network address (10.77.4.128) and before the broadcast address (10.77.4.143).
- ✗
10.77.4.112
Why it's wrong here
The address 10.77.4.112 is the network address of the /28 subnet 10.77.4.112/28, but that subnet only covers addresses from 112 to 127. The host address 10.77.4.141 is outside this range, so this subnet is entirely earlier than the one that contains the host. Therefore, it is an incorrect network address for the given host.
When this WOULD be correct
In a different question where the subnet mask was /24 and the host address was 10.77.4.112/24, option D would be the correct answer as it would represent the network address for that subnet, which spans from 10.77.4.0 to 10.77.4.255.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The 200-301 exam frequently reuses these exact scenarios with slightly different constraints.
✓10.77.4.128Correct answer▾
Why this is correct
The host address 10.77.4.141 falls within the /28 subnet that starts at 10.77.4.128, because the /28 block size is 16 addresses (128-143). The network address is the first address of that block, where all host bits are zero, so 10.77.4.128 is the correct network address. Any address in the range 10.77.4.129 through 10.77.4.142 is valid for hosts, while .143 is the broadcast.
✗10.77.4.143Wrong answer — click to see why▾
Why this is wrong here
Option B, 10.77.4.143, is incorrect because it falls within the usable host range of the subnet defined by 10.77.4.128/28, which spans from 10.77.4.129 to 10.77.4.142. The network address must always be the first address in the subnet.
★ When this WOULD be the correct answer
In a different question where the task is to identify the last usable host address in the subnet, 10.77.4.143 would be correct, as it is the highest address before the broadcast address of 10.77.4.143 in a /28 subnet.
Why candidates choose this
Candidates may choose this option because it is close to the network address and may confuse it with a valid host address, especially if they misinterpret the subnetting boundaries.
✗10.77.4.144Wrong answer — click to see why▾
Why this is wrong here
This option is wrong because 10.77.4.144 is not the network address for the subnet defined by 10.77.4.141/28; the correct network address is 10.77.4.128, which is the first address in the subnet range.
★ When this WOULD be the correct answer
If the question asked for the first usable host address in the subnet instead of the network address, then 10.77.4.144 could be considered correct, as it is the first address after the network address (10.77.4.128) and before the broadcast address (10.77.4.143).
Why candidates choose this
Candidates may choose this option due to confusion between the network address and the first usable host address, especially if they misinterpret the subnetting concept or overlook the specifics of address allocation.
✗10.77.4.112Wrong answer — click to see why▾
Why this is wrong here
Option D, 10.77.4.112, is incorrect because it does not fall within the subnet defined by the CIDR notation /28, which covers addresses from 10.77.4.128 to 10.77.4.143. The network address for this subnet is 10.77.4.128.
★ When this WOULD be the correct answer
In a different question where the subnet mask was /24 and the host address was 10.77.4.112/24, option D would be the correct answer as it would represent the network address for that subnet, which spans from 10.77.4.0 to 10.77.4.255.
Why candidates choose this
Candidates might choose option D due to a misunderstanding of subnetting, confusing the range of usable addresses with the network address, especially if they miscalculate the subnet boundaries.
Analysis generated from the official 200-301blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
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Related to this question
Learn chapter
IPv4 Addressing and Address Classes
Key term
Block size
Block size is the amount of data, measured in bytes, that a system reads or writes in a single operation, affecting storage efficiency and network performance.
Key term
Subnet
A subnet is a logical subdivision of an IP network, created by partitioning a larger network address space using subnet masks.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 200-301 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 200-301 exam.