The answer is to enable Packet Mirroring on a Compute Engine instance in the subnet to mirror all packets to a collector instance. This is correct because Packet Mirroring clones the full packet payload, not just metadata, and forwards it to a separate collector for deep packet inspection without disrupting the original traffic flow. VPC Flow Logs only capture header metadata like IPs and ports, not the payload content, so they cannot satisfy the requirement for actual payload capture. On the Google Professional Cloud Security Engineer exam, this question tests your understanding of network monitoring tools and their capabilities, often appearing as a trap where candidates confuse VPC Flow Logs with full packet capture. A common memory tip is: “Flow Logs tell you who talked; Packet Mirroring shows you what they said.”
PCSE Configuring network security Practice Question
This PCSE practice question tests your understanding of configuring network security. 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 financial services company needs to inspect all inbound and outbound packets from a subnet containing highly sensitive data for compliance. They have enabled VPC Flow Logs on that subnet, which record metadata such as source and destination IP, ports, and protocol. However, the security team requires the actual packet payload to perform deep packet inspection (DPI) for malicious patterns. They want to capture the packets without disrupting network traffic. Which additional configuration should be implemented to meet this requirement?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Enable Packet Mirroring on a Compute Engine instance in the subnet to mirror all packets to a collector instance.
Option C is correct because Packet Mirroring clones all packets (including payload) from a source instance in the subnet and forwards them to a collector instance for deep packet inspection, without disrupting the original traffic flow. VPC Flow Logs only capture metadata (headers, timestamps) and cannot include payload content, making Packet Mirroring the only solution that meets the requirement for actual packet payload capture.
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.
✗
Configure Cloud Armor to log all HTTP requests with full request body.
Why it's wrong here
Cloud Armor only logs HTTP-level logs, not all packets, and only if the load balancer is in front.
✗
Enable VPC Flow Logs with metadata capture set to 'include payload'.
Why it's wrong here
VPC Flow Logs do not support payload capture; they only provide metadata.
✓
Enable Packet Mirroring on a Compute Engine instance in the subnet to mirror all packets to a collector instance.
Why this is correct
Packet Mirroring captures full packet payloads without affecting live traffic.
Related concept
Read the scenario before looking for a memorised answer.
✗
Enable Cloud NAT logging to capture all outbound traffic payloads.
Why it's wrong here
Cloud NAT logging records metadata only, not payloads.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Google Cloud often tests the distinction between metadata logging (VPC Flow Logs) and full packet capture (Packet Mirroring), and the trap here is assuming VPC Flow Logs can be configured to include payloads, which is technically impossible in GCP.
Detailed technical explanation
How to think about this question
Packet Mirroring works by configuring a mirror policy on a VPC subnet or instance, which uses a GRE tunnel to encapsulate and forward mirrored packets to a collector instance running a packet capture tool like tcpdump or Wireshark. This allows security teams to perform DPI using tools like Snort or Suricata on the collector, while the original traffic remains unmodified. A key subtlety is that Packet Mirroring can generate significant bandwidth overhead, so it is typically used selectively on critical subnets rather than on all traffic.
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.
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.
Configuring network security — This question tests Configuring network security — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Enable Packet Mirroring on a Compute Engine instance in the subnet to mirror all packets to a collector instance. — Option C is correct because Packet Mirroring clones all packets (including payload) from a source instance in the subnet and forwards them to a collector instance for deep packet inspection, without disrupting the original traffic flow. VPC Flow Logs only capture metadata (headers, timestamps) and cannot include payload content, making Packet Mirroring the only solution that meets the requirement for actual packet payload capture.
What should I do if I get this PCSE 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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