CCNA Network Infrastructure and Connectivity Practice Question
A subnet uses the mask 255.255.255.252. How many usable host addresses are available in each subnet?
⚠ Common exam trap
Remember to exclude network and broadcast addresses when calculating usable host 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
✓
2
The mask 255.255.255.252 corresponds to /30. In practical terms, that gives 4 total addresses per subnet. After subtracting the network and broadcast addresses, 2 usable host addresses remain. This is a classic small-subnet calculation that often appears in point-to-point addressing scenarios.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
2
Why this is correct
Correct. A /30 subnet (255.255.255.252) has 2 host bits because 32-30=2. The total number of addresses is 2^2 = 4, which includes one network address and one broadcast address. Subtracting these two reserved addresses leaves exactly 4-2 = 2 usable host addresses. This is the standard point-to-point link subnet size.
- ✗
4
Why it's wrong here
Incorrect. 4 is the total number of IP addresses in a /30 subnet, not the number of usable hosts. The /30 block contains exactly 2^2 = 4 addresses: one network address, one broadcast address, and just two usable host addresses. The question specifically asks for usable hosts, so you must subtract the two reserved addresses from the total. Therefore 4 is the total address count, not the correct answer.
When this WOULD be correct
If the question asked for the total number of addresses in a subnet instead of usable addresses, then the answer would be 4, as it accounts for all IP addresses in the subnet, including the network and broadcast addresses.
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6
Why it's wrong here
Incorrect. 6 usable hosts would match a /29 subnet (255.255.255.248), which provides 2^3 - 2 = 6 usable addresses. A /30 subnet has only 2 host bits, so the maximum total addresses is 4, meaning you cannot possibly have 6 usable hosts. This answer may stem from confusing /30 with /29 or from incorrectly applying the usable-host formula. The correct usable count for /30 is 2.
When this WOULD be correct
If the question specified a subnet mask of 255.255.255.248 instead, which allows for 6 usable host addresses, then option C would be correct. This mask provides 8 total addresses, with 2 reserved for network and broadcast.
- ✗
14
Why it's wrong here
Incorrect. 14 usable hosts would require 4 host bits, because 2^4 - 2 = 14. Four host bits correspond to a /28 prefix length (255.255.255.240), not a /30. A /30 subnet has only 2 host bits, which is far too small to support 14 usable addresses. This answer likely confuses the /30 mask with a /28 mask.
When this WOULD be correct
If the question were to ask about a subnet mask of 255.255.255.240, which allows for 16 total addresses, the usable host addresses would be 14. In this case, option D would be the correct answer.
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.
✓2Correct answer▾
Why this is correct
Correct. A /30 subnet (255.255.255.252) has 2 host bits because 32-30=2. The total number of addresses is 2^2 = 4, which includes one network address and one broadcast address. Subtracting these two reserved addresses leaves exactly 4-2 = 2 usable host addresses. This is the standard point-to-point link subnet size.
✗4Wrong answer — click to see why▾
Why this is wrong here
The /30 subnet provides a total of 4 addresses, but one is the network address and one is the broadcast address, leaving only 2 usable host addresses. Saying 4 is incorrect because it counts the network and broadcast addresses as usable.
★ When this WOULD be the correct answer
If the question asked for the total number of addresses in a subnet instead of usable addresses, then the answer would be 4, as it accounts for all IP addresses in the subnet, including the network and broadcast addresses.
Why candidates choose this
Students often confuse the total number of addresses in a subnet with the number of usable host addresses. Since 2^2 = 4, they may mistakenly think all 4 are available for hosts.
✗6Wrong answer — click to see why▾
Why this is wrong here
A /30 subnet has only 2 bits for host addresses, yielding 2^2 = 4 total addresses, of which 2 are usable. 6 usable hosts would require at least 3 host bits (2^3 - 2 = 6), which corresponds to a /29 subnet.
★ When this WOULD be the correct answer
If the question specified a subnet mask of 255.255.255.248 instead, which allows for 6 usable host addresses, then option C would be correct. This mask provides 8 total addresses, with 2 reserved for network and broadcast.
Why candidates choose this
Some test-takers might incorrectly apply the formula 2^n - 2 and think n=3 gives 6, but they forget that /30 has only 2 host bits, not 3.
✗14Wrong answer — click to see why▾
Why this is wrong here
14 usable hosts correspond to a /28 subnet (255.255.255.240), which has 4 host bits (2^4 - 2 = 14). A /30 subnet has only 2 host bits, so it cannot provide 14 usable hosts.
★ When this WOULD be the correct answer
If the question were to ask about a subnet mask of 255.255.255.240, which allows for 16 total addresses, the usable host addresses would be 14. In this case, option D would be the correct answer.
Why candidates choose this
Students may confuse the subnet mask 255.255.255.252 with 255.255.255.240, as both are common masks, and mistakenly apply the host count of a /28 to a /30.
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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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.