CCNA Network Infrastructure and Connectivity Practice Question
A subnet uses the prefix /29. How many usable host addresses are available in each subnet?
⚠ Common exam trap
Remember to subtract the network and broadcast addresses from the total count to find usable 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
✓
6
A /29 prefix leaves 3 host bits, which creates 8 total addresses per subnet. In plain language, two of those addresses cannot be assigned to hosts because one identifies the subnet itself and one is reserved as the broadcast address. That leaves 6 usable host addresses. This is a standard CCNA calculation because it checks whether you understand both the total address count and the subtraction of the reserved addresses. Many candidates remember powers of two but forget to account for the network and broadcast addresses when the question asks for usable hosts. The safest process is to calculate the total size first and then reduce it by two. That is how you arrive at 6 usable addresses for a /29.
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 it's wrong here
Only 2 usable host addresses would correspond to a /30 prefix, which has 4 total addresses (2^2) and leaves 2 after subtracting network and broadcast. A /29 has one additional host bit (3 versus 2), doubling the total address count to 8 and therefore doubling the usable host count to 6, not 2. Choosing 2 would incorrectly apply the /30 calculation to a /29 subnet.
When this WOULD be correct
In a hypothetical question asking for the number of usable addresses in a /30 subnet, option A would be correct, as a /30 subnet has 4 total addresses, resulting in 2 usable host addresses.
- ✓
6
Why this is correct
A /29 prefix leaves 3 host bits (32 - 29 = 3), yielding 2^3 = 8 total IPv4 addresses in the subnet. After reserving one address for the network identifier and one for the directed broadcast address, exactly 8 - 2 = 6 addresses remain assignable to hosts. This matches the formula 2^(32 - prefix) - 2, which is the standard way to calculate usable host capacity.
- ✗
14
Why it's wrong here
A total of 14 usable hosts would require 16 total addresses, meaning 4 host bits, which is a /28 prefix (32 - 4 = 28). Since a /29 has only 3 host bits, its total address space is half that of a /28: 8 total addresses instead of 16. Subtracting 2 reserved addresses from 8 produces 6 usable addresses, so 14 is a mismatch that assumes a shorter prefix than the given /29.
When this WOULD be correct
If the question specified a /28 subnet instead of /29, then option C would be correct, as a /28 subnet allows for 16 total IP addresses, resulting in 14 usable host addresses after accounting for the network and broadcast addresses.
- ✗
30
Why it's wrong here
Getting 30 usable addresses would necessitate 32 total addresses, which requires 5 host bits and thus a /27 prefix (32 - 5 = 27). A /29 is two bits longer, which reduces the host bits to 3 and correspondingly reduces the total addresses by a factor of 4—from 32 down to 8. After removing the network and broadcast addresses, only 6 remain usable, so 30 is far too large and corresponds to a different prefix length.
When this WOULD be correct
In a different context, if the question asked about a subnet with a prefix of /26, which allows for 62 usable host addresses, option D could be correct. This would require candidates to calculate usable addresses based on a larger subnet size.
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.
✓6Correct answer▾
Why this is correct
A /29 prefix leaves 3 host bits (32 - 29 = 3), yielding 2^3 = 8 total IPv4 addresses in the subnet. After reserving one address for the network identifier and one for the directed broadcast address, exactly 8 - 2 = 6 addresses remain assignable to hosts. This matches the formula 2^(32 - prefix) - 2, which is the standard way to calculate usable host capacity.
✗2Wrong answer — click to see why▾
Why this is wrong here
Option A is incorrect because a /29 subnet provides 8 total IP addresses, of which 6 are usable for hosts after accounting for the network and broadcast addresses.
★ When this WOULD be the correct answer
In a hypothetical question asking for the number of usable addresses in a /30 subnet, option A would be correct, as a /30 subnet has 4 total addresses, resulting in 2 usable host addresses.
Why candidates choose this
Candidates may choose this option due to confusion between the total number of addresses and the usable ones, or they might mistakenly associate /29 with a smaller subnet size like /30, leading to the miscalculation.
✗14Wrong answer — click to see why▾
Why this is wrong here
Option C is wrong because a /29 subnet provides 8 total IP addresses, of which 6 are usable for hosts after reserving one for the network address and one for the broadcast address.
★ When this WOULD be the correct answer
If the question specified a /28 subnet instead of /29, then option C would be correct, as a /28 subnet allows for 16 total IP addresses, resulting in 14 usable host addresses after accounting for the network and broadcast addresses.
Why candidates choose this
Candidates might choose option C due to a misunderstanding of subnetting, mistakenly calculating the usable addresses by only considering the total number of addresses without accounting for the reserved network and broadcast addresses.
✗30Wrong answer — click to see why▾
Why this is wrong here
Option D is incorrect because a /29 subnet provides 8 total IP addresses, of which 6 are usable for hosts after accounting for the network and broadcast addresses. Therefore, stating that there are 30 usable addresses is inaccurate.
★ When this WOULD be the correct answer
In a different context, if the question asked about a subnet with a prefix of /26, which allows for 62 usable host addresses, option D could be correct. This would require candidates to calculate usable addresses based on a larger subnet size.
Why candidates choose this
Candidates may choose option D due to confusion between the total number of addresses and the usable ones, or they might mistakenly recall common subnet sizes that yield higher usable addresses, leading to an overestimation.
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
Subnet
A subnet is a logical subdivision of an IP network, created by partitioning a larger network address space using subnet masks.
Key term
Usable hosts
Usable hosts are the IP addresses in a subnet that can actually be assigned to devices like computers, printers, or servers, excluding the network and broadcast addresses.
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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.