This CV0-004 practice question tests your understanding of troubleshooting. 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.
A cloud administrator is troubleshooting connectivity issues between two virtual networks in different regions. The VNets are peered, but instances cannot communicate. The administrator verifies that the peering status is 'Connected' and route tables appear correct. Which of the following should be checked next?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Network Security Group (NSG) rules on the instances and subnets
Even when VNet peering status shows 'Connected' and route tables are correct, Network Security Group (NSG) rules can still block traffic. NSGs act as a stateful firewall at the subnet or NIC level, and by default they deny all inbound traffic unless explicitly allowed. Since the administrator has already verified routing, the next logical step is to check NSG rules for any implicit deny or missing allow rules that could be dropping the inter-region traffic.
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.
✓
Network Security Group (NSG) rules on the instances and subnets
Why this is correct
Correct; NSGs can block traffic even if VNet peering is established.
Related concept
Read the scenario before looking for a memorised answer.
✗
DNS resolution settings
Why it's wrong here
Incorrect; DNS affects name resolution, not direct IP connectivity.
✗
Gateway subnet configuration
Why it's wrong here
Incorrect; gateways are not required for VNet peering.
✗
Service endpoint status
Why it's wrong here
Incorrect; service endpoints are for accessing Azure PaaS services.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates assume a 'Connected' peering status guarantees traffic flow, but they overlook that NSGs can silently drop traffic even when peering and routing are correctly configured.
Detailed technical explanation
How to think about this question
NSGs evaluate rules in priority order (lowest number first) and apply a default implicit deny for all traffic not explicitly allowed. For inter-region VNet peering, traffic flows over the Microsoft backbone, so NSGs are the primary control point after routing. A common subtlety is that NSG flow logs (enabled via Network Watcher) can be used to confirm whether packets are being dropped, and the 'effective security rules' blade in the portal shows the combined rules applied to a NIC or subnet.
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
A security administrator must allow nursing staff to reach a patient records server while blocking access from the guest Wi-Fi VLAN. After applying an extended ACL, traffic is still blocked from nursing workstations. The ACL was applied outbound instead of inbound on the wrong interface. Questions like this test ACL direction and placement rules.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Troubleshooting — This question tests Troubleshooting — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Network Security Group (NSG) rules on the instances and subnets — Even when VNet peering status shows 'Connected' and route tables are correct, Network Security Group (NSG) rules can still block traffic. NSGs act as a stateful firewall at the subnet or NIC level, and by default they deny all inbound traffic unless explicitly allowed. Since the administrator has already verified routing, the next logical step is to check NSG rules for any implicit deny or missing allow rules that could be dropping the inter-region traffic.
What should I do if I get this CV0-004 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.
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Question Discussion
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