Quick Answer
The answer is VPC Flow Logs, the correct feature to enable for diagnosing packet drops and high latency in a VPC. VPC Flow Logs capture metadata about IP traffic flowing to and from network interfaces, including details on accepted and rejected packets, which directly reveals where drops occur. On the Google Professional Cloud Network Engineer exam, this question tests your ability to distinguish between monitoring, logging, and traffic inspection tools—a common trap is confusing VPC Flow Logs with Packet Mirroring, which captures full packet payloads for deep analysis rather than logging metadata. Remember that Flow Logs are for visibility into traffic patterns and drops, not for capturing content. A useful memory tip: think of Flow Logs as a “flight recorder” for your VPC traffic—they log the journey, not the cargo.
This PCNE practice question tests your understanding of implementing a virtual private cloud. 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.
An engineer is troubleshooting high latency in a VPC and suspects packet drops. Which VPC feature should they enable to get detailed information about network traffic?
Cloud NAT logging
Why wrong: NAT logging only covers NATted traffic.
VPC Flow Logs
VPC Flow Logs sample and log network flows, useful for diagnostics.
Packet Mirroring
Why wrong: Packet Mirroring copies traffic for inspection but is very resource-intensive.
Traffic Director
Why wrong: Traffic Director is for service mesh, not traffic logging.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
VPC Flow Logs
Option A is correct because VPC Flow Logs capture information about IP traffic going to and from network interfaces. They help diagnose packet drops and latency issues. Option B is incorrect because Cloud NAT logging provides logs about NAT connections. Option C is incorrect because Packet Mirroring is for capturing and inspecting traffic, not for logging. Option D is incorrect because Traffic Director is a service mesh control plane, not a traffic logging tool.
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
Cloud NAT logging
Why it's wrong here
NAT logging only covers NATted traffic.
VPC Flow Logs
Why this is correct
VPC Flow Logs sample and log network flows, useful for diagnostics.
Related concept
Static NAT maps one inside address to one outside address.
Packet Mirroring
Why it's wrong here
Packet Mirroring copies traffic for inspection but is very resource-intensive.
Traffic Director
Why it's wrong here
Traffic Director is for service mesh, not traffic logging.
Common exam traps
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Detailed technical explanation
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
Key takeaway
NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Real-world example
A healthcare organisation deploys an application with a public-facing web tier and a private database tier. The database subnet has no public IP and only accepts connections from the web tier's security group. Questions like this test whether you can design cloud network isolation using VNets/VPCs, subnets, and security group rules.
What to study next
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related PCNE NAT questions on configuration and troubleshooting.
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FAQ
Implementing a Virtual Private Cloud — This question tests Implementing a Virtual Private Cloud — Static NAT maps one inside address to one outside address..
The correct answer is: VPC Flow Logs — Option A is correct because VPC Flow Logs capture information about IP traffic going to and from network interfaces. They help diagnose packet drops and latency issues. Option B is incorrect because Cloud NAT logging provides logs about NAT connections. Option C is incorrect because Packet Mirroring is for capturing and inspecting traffic, not for logging. Option D is incorrect because Traffic Director is a service mesh control plane, not a traffic logging tool.
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related PCNE NAT questions on configuration and troubleshooting.
Static NAT maps one inside address to one outside address.
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Last reviewed: Jun 24, 2026
This PCNE practice question is part of Courseiva's free Google Cloud 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 PCNE exam.
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