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Managing, Monitoring, and Optimising Network Operations →mediumMultiple ChoiceObjective-mapped

PCNE Practice Question: Managing, Monitoring, and Optimising Network Operations

This PCNE practice question tests your understanding of managing, monitoring, and optimising network operations. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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 has enabled VPC Flow Logs on a subnet with the default sample rate. They notice that only 50% of flows are being logged. What is the most likely reason?

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.

A
Flow logs only capture TCP traffic
Why wrong: Flow logs capture UDP, TCP, and other protocols.
B
The sample rate is set to 50% by default
Correct: The default sampling rate is 50%.
C
Flow logs are disabled by default on all subnets
Why wrong: They are enabled, but default sampling rate is 50%.
D
The subnet is using a custom sample rate of 50%
Why wrong: Default is 50%.

Full breakdown with real-world context →

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

✓

The sample rate is set to 50% by default

The default sampling rate for VPC Flow Logs is 50%. This means only half of the network flows are captured to reduce cost and volume.

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.

✗
Flow logs only capture TCP traffic
Why it's wrong here
Flow logs capture UDP, TCP, and other protocols.
✓
The sample rate is set to 50% by default
Why this is correct
Correct: The default sampling rate is 50%.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
CIDR notation defines the prefix length.
✗
Flow logs are disabled by default on all subnets
Why it's wrong here
They are enabled, but default sampling rate is 50%.
✗
The subnet is using a custom sample rate of 50%
Why it's wrong here
Default is 50%.

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 startup's cloud architect reviews their monthly bill and notices costs are higher than expected for a long-running batch job. Switching from on-demand instances to Reserved Instances — or using Spot/Preemptible VMs — can reduce compute costs by up to 72 %. Questions like this test whether you understand the tradeoffs between commitment, flexibility, and cost across cloud pricing models.

Visual reference

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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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: The sample rate is set to 50% by default — The default sampling rate for VPC Flow Logs is 50%. This means only half of the network flows are captured to reduce cost and volume.

What should I do if I get this PCNE question wrong?

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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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.