The answer is a /26 subnet prefix. This is correct because a /26 subnet in Azure provides 64 total IP addresses, calculated as 2^(32-26), with 62 usable for VM NICs after Azure reserves five addresses for networking purposes. For your AZ-104 exam, this question tests your ability to match subnet size to workload requirements, specifically ensuring you account for Azure’s five reserved IPs (network, gateway, broadcast, and two internal DNS) when calculating usable addresses. A common trap is forgetting that Azure reserves more addresses than the traditional two, so a /27 (32 total, 27 usable) would be too tight for 30 NICs, while a /26 gives comfortable headroom for growth. The key takeaway: always subtract five from the total IP count to get usable Azure addresses. Memory tip: “/26 gives 64 total, 62 usable—plenty for 30 NICs plus room to expand.”
AZ-104 Implement and Manage Virtual Networking Practice Question
This AZ-104 practice question tests your understanding of implement and manage virtual networking. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
Exhibit
Planned VNet address space: 10.70.0.0/16
Subnet A requirement: about 30 VM NICs
Subnet B requirement: about 8 VM NICs and one future jump box
Azure reserves 5 IP addresses in each subnet
Based on the exhibit, which subnet prefix should be used for Subnet A so it can support about 30 VM NICs?
Planned VNet address space: 10.70.0.0/16
Subnet A requirement: about 30 VM NICs
Subnet B requirement: about 8 VM NICs and one future jump box
Azure reserves 5 IP addresses in each subnet
A
/28
Why wrong: A /28 subnet provides too few usable addresses after Azure reservations. It cannot support about 30 VM NICs.
B
/27
Why wrong: A /27 subnet has 32 total addresses, but Azure reserves 5 of them, leaving only 27 usable addresses. That is still short of the requirement for about 30 VM NICs.
C
/26
A /26 subnet is the smallest option listed that can support about 30 VM NICs after Azure reserves its five addresses. /26 provides 64 total addresses and enough usable IPs for the requirement, leaving a little room for growth. This is the most efficient choice among the options shown.
D
/25
Why wrong: A /25 subnet would also work, but it uses more address space than necessary. For an easy planning question, the smallest prefix that meets the need is the better answer.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
/26
Option C (/26) is correct because a /26 subnet provides 64 IP addresses (2^(32-26) = 64), of which 62 are usable for VM NICs after reserving the network address and broadcast address. This comfortably supports about 30 VM NICs while leaving room for growth.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
/28
Why it's wrong here
A /28 subnet provides too few usable addresses after Azure reservations. It cannot support about 30 VM NICs.
✗
/27
Why it's wrong here
A /27 subnet has 32 total addresses, but Azure reserves 5 of them, leaving only 27 usable addresses. That is still short of the requirement for about 30 VM NICs.
✓
/26
Why this is correct
A /26 subnet is the smallest option listed that can support about 30 VM NICs after Azure reserves its five addresses. /26 provides 64 total addresses and enough usable IPs for the requirement, leaving a little room for growth. This is the most efficient choice among the options shown.
Related concept
Read the scenario before looking for a memorised answer.
✗
/25
Why it's wrong here
A /25 subnet would also work, but it uses more address space than necessary. For an easy planning question, the smallest prefix that meets the need is the better answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often forget Azure reserves five IP addresses per subnet (not just the network and broadcast), leading them to incorrectly choose /27 thinking 30 usable IPs are enough, when in reality only 25 are available.
Detailed technical explanation
How to think about this question
In Azure, each subnet reserves five IP addresses: the first four (x.x.x.0–3) and the last one (x.x.x.255 for /24 or the broadcast address). For a /27 subnet, this reduces usable IPs from 30 to 25, which is insufficient for 30 NICs. A /26 subnet yields 64 total IPs, minus 5 Azure-reserved = 59 usable, comfortably supporting 30 NICs with room for future expansion. This reservation behavior is specific to Azure and differs from on-premises subnet calculations.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
An e-commerce site experiences heavy traffic on Black Friday and near-zero traffic during off-peak weeks. Rather than provisioning permanent large VMs, the team uses auto-scaling groups that add capacity automatically under load and reduce it overnight. Questions like this test whether you understand elasticity, availability zones, and cloud compute scaling patterns.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this AZ-104 question in full detail.
Implement and Manage Virtual Networking — This question tests Implement and Manage Virtual Networking — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: /26 — Option C (/26) is correct because a /26 subnet provides 64 IP addresses (2^(32-26) = 64), of which 62 are usable for VM NICs after reserving the network address and broadcast address. This comfortably supports about 30 VM NICs while leaving room for growth.
What should I do if I get this AZ-104 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
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Variation 1. Based on the exhibit, which subnet prefix is the smallest that can support the planned resources in Azure?
medium
A./27
✓ B./26
C./25
D./24
Why B: The subnet prefix /26 provides 64 IP addresses per subnet (2^(32-26) = 64), of which 59 are usable after Azure reserves 5 addresses (first 4 and last 1). The planned resources require 50 IP addresses, so /26 is the smallest prefix that meets this requirement without waste. A /27 would only provide 32 total addresses (27 usable), which is insufficient.
Last reviewed: Jun 11, 2026
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