The answer is the NSG on VM2’s subnet does not allow inbound traffic from VM1’s VNet address space. This is correct because VNet peering connects the virtual networks at the network layer, but it does not automatically override or bypass Network Security Group rules; each subnet’s NSG must explicitly permit traffic from the peered VNet’s IP range. Even though both NSGs have rules allowing HTTP from each other’s IP ranges, the key detail is that the rule on VM2’s subnet must be configured to accept inbound traffic from the entire 10.0.1.0/24 address space of VM1’s VNet, not just from a specific IP. On the AZ-500 exam, this scenario tests your understanding that NSGs are stateful but still require explicit inbound rules for peered VNet traffic—a common trap is assuming peering alone grants full access. Remember the mnemonic: “Peering opens the door, but NSGs decide who walks through.”
AZ-500 Secure networking Practice Question
This AZ-500 practice question tests your understanding of secure networking. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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.
You are troubleshooting connectivity between two Azure virtual machines in different VNets that are peered. VM1 (10.0.1.4) cannot reach VM2 (10.0.2.4) on port 80. Both VNets have NSGs allowing HTTP traffic from each other's IP ranges. The VNet peering is in 'Connected' state. You verify that the VMs' operating system firewalls allow HTTP. What is the most likely cause of the connectivity issue?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The NSG on VM2's subnet does not allow inbound traffic from VM1's VNet address space.
Option B is correct because VNet peering does not automatically allow traffic through the peer's NSG; you must explicitly configure NSG rules to allow traffic from the peered VNet's address space. Option A is wrong because the peering status is Connected, so it is not broken. Option C is wrong because NSGs are stateful, so return traffic is allowed automatically. Option D is wrong because Azure Firewall might block traffic but is not mentioned in the scenario.
Key principle: Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
NSGs are not stateful and require explicit outbound rules.
Why it's wrong here
NSGs are stateful; outbound return traffic is automatically allowed.
✗
The VNet peering status is disconnected.
Why it's wrong here
The peering is in 'Connected' state, so it is working.
✗
Azure Firewall is blocking traffic between the VNets.
Common exam trap: usable hosts are not the same as total addresses
Subnetting questions often tempt you into counting all addresses. In normal IPv4 subnets, the network and broadcast addresses are not usable host addresses.
Trap categories for this question
Scenario analysis trap
No Azure Firewall is mentioned in the scenario.
Detailed technical explanation
How to think about this question
Subnetting questions test whether you can identify the network, broadcast address, usable range, mask and correct subnet. Slow down enough to calculate the block size correctly.
KKey Concepts to Remember
CIDR notation defines the prefix length.
Block size helps identify subnet boundaries.
Network and broadcast addresses are not usable hosts in normal IPv4 subnets.
The required host count determines the smallest suitable subnet.
TExam Day Tips
→Write the block size before choosing the subnet.
→Check whether the question asks for hosts, subnets or a specific address range.
→Do not confuse /24, /25, /26 and /27 host counts.
Key takeaway
Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
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-500 question in full detail.
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related AZ-500 subnetting questions on CIDR, address ranges, and subnet selection.
Secure networking — This question tests Secure networking — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: The NSG on VM2's subnet does not allow inbound traffic from VM1's VNet address space. — Option B is correct because VNet peering does not automatically allow traffic through the peer's NSG; you must explicitly configure NSG rules to allow traffic from the peered VNet's address space. Option A is wrong because the peering status is Connected, so it is not broken. Option C is wrong because NSGs are stateful, so return traffic is allowed automatically. Option D is wrong because Azure Firewall might block traffic but is not mentioned in the scenario.
What should I do if I get this AZ-500 question wrong?
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related AZ-500 subnetting questions on CIDR, address ranges, and subnet selection.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
CIDR notation defines the prefix length.
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