- A
Export logs only to BigQuery instead of Stackdriver
Why wrong: Export destination does not reduce volume; it just moves data.
- B
Filter logs to only include traffic on port 80
Why wrong: This removes potentially important data.
- C
Disable VPC Flow Logs on subnets with low traffic
Why wrong: This would reduce volume but may miss critical flows.
- D
Set the sampling rate to 0.25
Reducing sampling from 0.5 to 0.25 cuts log volume by half, achieving ~75% reduction from original.
Question 854 of 1,000
PCNE Practice Question: Managing, Monitoring, and Optimising Network Operations
This PCNE practice question tests your understanding of managing, monitoring, and optimising network operations. 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 company is using VPC Flow Logs to analyze traffic patterns. They need to reduce the volume of logs by approximately 75% while still capturing representative data for troubleshooting. What is the most effective configuration change?
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Set the sampling rate to 0.25
VPC Flow Logs supports a configurable sampling rate between 0.25 and 1.0, with a default of 0.5 (50%). Setting the sampling rate to 0.25 (25%) reduces the log volume by 75% compared to capturing all flows (1.0) and by 50% compared to the default. This still captures representative samples for troubleshooting, making it the most effective option among the choices.
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.
- ✗
Export logs only to BigQuery instead of Stackdriver
Why it's wrong here
Export destination does not reduce volume; it just moves data.
- ✗
Filter logs to only include traffic on port 80
Why it's wrong here
This removes potentially important data.
- ✗
Disable VPC Flow Logs on subnets with low traffic
Why it's wrong here
This would reduce volume but may miss critical flows.
- ✓
Set the sampling rate to 0.25
Why this is correct
Reducing sampling from 0.5 to 0.25 cuts log volume by half, achieving ~75% reduction from original.
Related concept
CIDR notation defines the prefix length.
Common exam traps
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.
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
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
Got this wrong? Here's your next step.
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related PCNE subnetting questions on CIDR, address ranges, and subnet selection.
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Managing, Monitoring, and Optimising Network Operations — study guide chapter
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FAQ
Questions learners often ask
What does this PCNE question test?
Managing, Monitoring, and Optimising Network Operations — This question tests Managing, Monitoring, and Optimising Network Operations — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: Set the sampling rate to 0.25 — VPC Flow Logs supports a configurable sampling rate between 0.25 and 1.0, with a default of 0.5 (50%). Setting the sampling rate to 0.25 (25%) reduces the log volume by 75% compared to capturing all flows (1.0) and by 50% compared to the default. This still captures representative samples for troubleshooting, making it the most effective option among the choices.
What should I do if I get this PCNE 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 PCNE subnetting questions on CIDR, address ranges, and subnet selection.
What is the key concept behind this question?
CIDR notation defines the prefix length.
About these practice questions
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Last reviewed: Jul 4, 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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