CCNA Network Infrastructure and Connectivity Practice Question
A host uses the subnet mask 255.255.255.192. How many usable host addresses exist in each subnet?
⚠ Common exam trap
Be careful not to confuse total addresses with usable addresses; always subtract the network and broadcast addresses.
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
✓
62
The mask 255.255.255.192 corresponds to /26. That leaves 6 host bits, which means each subnet contains 64 total addresses. After excluding the network and broadcast addresses, 62 usable host addresses remain. This is a standard host-capacity question. The safest approach is to convert the mask to the prefix, determine the total addresses from the number of host bits, and then subtract the two reserved addresses.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
30
Why it's wrong here
This option is incorrect because 255.255.255.192 is a /26 prefix, which creates subnets with 2^(32-26) = 2^6 = 64 total addresses. After reserving the network address and the broadcast address, exactly 62 usable host addresses remain. The value 30 would be correct for a /27 subnet (255.255.255.224), which provides 32 total addresses, so choosing 30 likely stems from mistakenly applying the /27 block size (32) and subtracting the two reserved addresses from that smaller range.
When this WOULD be correct
If the question specified a subnet mask of 255.255.255.224 instead, which allows for 30 usable host addresses, then option A would be the correct answer. This would change the total number of addresses available in the subnet.
- ✓
62
Why this is correct
This is the correct answer because the subnet mask 255.255.255.192 translates to a /26 prefix, leaving 32 - 26 = 6 bits for host addressing. With 6 host bits, the total number of addresses in each subnet is 2^6 = 64, and from that total the network address (all host bits zero) and the broadcast address (all host bits one) must be subtracted. This yields 64 - 2 = 62 usable host addresses, which matches the requirement for a /26 subnet.
- ✗
126
Why it's wrong here
This option is incorrect for the given subnet mask because /26 (255.255.255.192) yields only 64 total addresses per subnet, not 128. A subnet with 126 usable hosts requires 128 total addresses, which corresponds to a /25 mask (255.255.255.128). The confusion here often arises from thinking of the third octet's decimal value (192) as implying 128 available from some quick binary shortcut, but 192 in binary is 11000000, meaning only 6 host bits exist, so the usable count is 62—not 126.
When this WOULD be correct
If the question asked about a subnet mask of 255.255.255.0, which allows for 256 total addresses, then option C would be correct, as it would provide 254 usable addresses (256 total minus 2).
- ✗
254
Why it's wrong here
A /26 prefix (255.255.255.192) yields 2⁶ = 64 total addresses per subnet, of which the network address and broadcast address are reserved, leaving 62 usable hosts — not 254. The figure 254 corresponds to a /24 subnet (255.255.255.0), which provides 256 total addresses minus two reserved. This option is tempting because 254 is a common default for a Class C network, leading one to mistakenly apply that familiar value without recalculating for the smaller subnet mask specified.
When this WOULD be correct
If the question were modified to ask about a subnet mask of 255.255.255.0, which allows for 256 total addresses and 254 usable addresses after accounting for the network and broadcast addresses, then option D would be correct.
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.
✓62Correct answer▾
Why this is correct
This is the correct answer because the subnet mask 255.255.255.192 translates to a /26 prefix, leaving 32 - 26 = 6 bits for host addressing. With 6 host bits, the total number of addresses in each subnet is 2^6 = 64, and from that total the network address (all host bits zero) and the broadcast address (all host bits one) must be subtracted. This yields 64 - 2 = 62 usable host addresses, which matches the requirement for a /26 subnet.
✗30Wrong answer — click to see why▾
Why this is wrong here
The subnet mask 255.255.255.192 is /26, which provides 64 total addresses per subnet. Subtracting the network and broadcast addresses leaves 62 usable hosts, not 30. 30 usable hosts corresponds to a /27 subnet mask (255.255.255.224).
★ When this WOULD be the correct answer
If the question specified a subnet mask of 255.255.255.224 instead, which allows for 30 usable host addresses, then option A would be the correct answer. This would change the total number of addresses available in the subnet.
Why candidates choose this
Students often confuse the number of bits borrowed; a /27 mask (255.255.255.224) yields 30 usable hosts, and they might mistakenly apply that to a /26 mask.
✗126Wrong answer — click to see why▾
Why this is wrong here
126 usable hosts would require a /25 subnet mask (255.255.255.128), which provides 128 total addresses. The given mask /26 provides only 64 total addresses, so 126 is incorrect.
★ When this WOULD be the correct answer
If the question asked about a subnet mask of 255.255.255.0, which allows for 256 total addresses, then option C would be correct, as it would provide 254 usable addresses (256 total minus 2).
Why candidates choose this
Students may misremember the host counts for /25 and /26, or incorrectly calculate the number of hosts by forgetting to subtract the network and broadcast addresses.
✗254Wrong answer — click to see why▾
Why this is wrong here
254 usable hosts corresponds to a /24 subnet mask (255.255.255.0), which provides 256 total addresses. The mask 255.255.255.192 is /26, which is two bits longer, resulting in only 64 total addresses.
★ When this WOULD be the correct answer
If the question were modified to ask about a subnet mask of 255.255.255.0, which allows for 256 total addresses and 254 usable addresses after accounting for the network and broadcast addresses, then option D would be correct.
Why candidates choose this
A common mistake is to assume that any subnet mask with 255 in the first three octets yields 254 hosts, but the fourth octet's value determines the actual host count.
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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Collision Domains and Broadcast Domains
Key term
Subnet
A subnet is a logical subdivision of an IP network, created by partitioning a larger network address space using subnet masks.
Key term
Subnet mask
A subnet mask is a 32-bit number that helps a computer or network device determine which part of an IP address identifies the network and which part identifies the host device on that network.
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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.