N10-009 Networking Concepts Practice Question
A network engineer is designing a subnet to accommodate 50 devices in a single broadcast domain. The engineer uses a /26 subnet mask. How many usable host addresses are available?
⚠ Common exam trap
The trap here is that candidates often forget to subtract the network and broadcast addresses, or they confuse the total addresses (64) with usable addresses (62), leading them to pick 64 or misapply the formula for a different prefix length.
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
A /26 subnet mask provides 2^(32-26) = 64 total addresses. Subtracting the network and broadcast addresses leaves 62 usable host addresses. This is sufficient for 50 devices in a single broadcast domain.
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
A subnet providing 30 usable host addresses is a /27, which allocates 5 bits for the host portion (32 - 27 = 5). This allows for 2^5 = 32 total addresses, from which 32 - 2 = 30 usable addresses can be assigned to devices. This quantity is insufficient to accommodate 50 devices, as it falls short by 20 required addresses, making it impossible to connect all specified devices to the network.
When this WOULD be correct
This would be correct if the question specified a /27 subnet mask (255.255.255.224), which provides 32 total addresses minus 2 = 30 usable hosts.
- ✓
62
Why this is correct
A /26 subnet mask allocates 26 bits to the network portion, leaving 6 bits for host addresses (32 - 26 = 6). This configuration provides 2^6 = 64 total IP addresses within the subnet. After reserving two addresses for the network identifier and the broadcast address, 64 - 2 = 62 usable host addresses remain. This quantity is perfectly suitable for accommodating 50 devices while also providing a comfortable buffer for future network expansion.
- ✗
126
Why it's wrong here
This number of usable addresses corresponds to a /25 subnet mask, which dedicates 7 bits to the host portion (32 - 25 = 7). Consequently, 2^7 = 128 total addresses are available, yielding 128 - 2 = 126 usable host addresses. While technically sufficient for 50 devices, this subnet is significantly larger than necessary, leading to inefficient utilization of the IP address space and creating a larger broadcast domain than optimal for the specified number of devices.
When this WOULD be correct
This option would be correct if the question specified a /25 subnet mask (255.255.255.128) instead of /26. For example: 'A network engineer is designing a subnet to accommodate 100 devices. The engineer uses a /25 subnet mask. How many usable host addresses are available?'
- ✗
254
Why it's wrong here
Obtaining 254 usable host addresses requires a /24 subnet mask, which means 8 bits are designated for the host portion (32 - 24 = 8). This configuration results in 2^8 = 256 total addresses, with 256 - 2 = 254 usable for devices. This subnet size is excessively large for a requirement of only 50 devices, resulting in substantial IP address waste and a broadcast domain that is much larger than required, potentially increasing network overhead and reducing efficiency.
When this WOULD be correct
This option would be correct if the question specified a /24 subnet mask (e.g., 'How many usable host addresses are available with a /24 subnet mask?').
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 N10-009 exam frequently reuses these exact scenarios with slightly different constraints.
✓62Correct answer▾
Why this is correct
A /26 subnet mask allocates 26 bits to the network portion, leaving 6 bits for host addresses (32 - 26 = 6). This configuration provides 2^6 = 64 total IP addresses within the subnet. After reserving two addresses for the network identifier and the broadcast address, 64 - 2 = 62 usable host addresses remain. This quantity is perfectly suitable for accommodating 50 devices while also providing a comfortable buffer for future network expansion.
✗30Wrong answer — click to see why▾
Why this is wrong here
A /26 subnet provides 2^(32-26) = 64 total addresses, with 2 reserved for network and broadcast, leaving 62 usable. Option A (30) corresponds to a /27 subnet, not /26.
★ When this WOULD be the correct answer
This would be correct if the question specified a /27 subnet mask (255.255.255.224), which provides 32 total addresses minus 2 = 30 usable hosts.
Why candidates choose this
Candidates often miscalculate by subtracting 2 from 32 (thinking /26 gives 32 addresses) or confuse /26 with /27 due to common subnetting errors.
✗126Wrong answer — click to see why▾
Why this is wrong here
A /26 subnet mask provides 64 total addresses, with 62 usable host addresses (2^6 - 2 = 62). Option C (126) corresponds to a /25 subnet mask, which is not used in this question.
★ When this WOULD be the correct answer
This option would be correct if the question specified a /25 subnet mask (255.255.255.128) instead of /26. For example: 'A network engineer is designing a subnet to accommodate 100 devices. The engineer uses a /25 subnet mask. How many usable host addresses are available?'
Why candidates choose this
Candidates may mistakenly calculate 2^7 - 2 = 126, confusing the /26 subnet (6 host bits) with a /25 subnet (7 host bits), or they might forget to subtract the network and broadcast addresses.
✗254Wrong answer — click to see why▾
Why this is wrong here
A /26 subnet mask provides 64 total addresses, with 62 usable host addresses (64 - 2 for network and broadcast). Option D (254) corresponds to a /24 subnet mask, not /26.
★ When this WOULD be the correct answer
This option would be correct if the question specified a /24 subnet mask (e.g., 'How many usable host addresses are available with a /24 subnet mask?').
Why candidates choose this
Candidates may confuse subnet masks, thinking /26 provides 254 usable addresses due to misremembering the host bits or incorrectly applying the formula 2^(32-26)-2.
Analysis generated from the official N10-009blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
Visual reference
Go deeper
Related to this question
Learn chapter
Network Virtualization and VXLAN
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
Broadcast domain
A broadcast domain is a network segment where any device can send a broadcast message that all other devices on that segment will receive and process.
About these practice questions
One of 464 original N10-009 practice questions on Courseiva, each with a full explanation and wrong-answer analysis — not exam dumps or protected exam content. Learn why practice questions differ from exam dumps →
Same concept, more angles
1 more way this is tested on N10-009
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A network administrator is configuring IP addresses for a new subnet. The network address is 192.168.1.0 with a subnet mask of 255.255.255.240. How many usable host addresses are available on this subnet?
easy- ✓ A.14
- B.16
- C.30
- D.62
Why A: The subnet mask 255.255.255.240 (or /28) provides 16 total addresses per subnet. The network address (192.168.1.0) and the broadcast address (192.168.1.15) are reserved, leaving 16 - 2 = 14 usable host addresses. This is calculated as 2^(32-28) - 2 = 2^4 - 2 = 16 - 2 = 14.
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This N10-009 practice question is part of Courseiva's free CompTIA 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 N10-009 exam.