- A
Set the minimum ports per VM to a reasonable value
This guarantees each VM gets a minimum number of ports.
- B
Set the NAT IP allocation to manual
Manual allocation allows configuring per-VM port limits.
- C
Enable logging on the NAT gateway
Why wrong: Logging helps monitoring but does not prevent port exhaustion.
- D
Enable endpoint-independent mapping
Why wrong: This is a UDP optimization, not for port exhaustion prevention.
- E
Set the maximum ports per VM to a reasonable value
This limits how many ports a single VM can use, preventing exhaustion.
Question 98 of 1,000
PCNE Implementing VPC Instances Practice Question
This PCNE practice question tests your understanding of implementing vpc instances. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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 needs to configure Cloud NAT with logging enabled to monitor traffic from a specific subnet. The NAT gateway uses automatic NAT IP allocation. The engineer wants to ensure that if a single VM uses many connections, it does not exhaust the available ports for other VMs. Which THREE settings should be configured? (Choose THREE.)
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 minimum ports per VM to a reasonable value
To prevent port exhaustion, the engineer should enable manual port allocation to set limits, configure endpoint-independent mapping for UDP (not directly related to port exhaustion), and set a minimum ports per VM to guarantee each VM gets a baseline. Manual allocation allows setting a maximum number of ports per VM, which prevents a single VM from using all ports.
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.
- ✓
Set the minimum ports per VM to a reasonable value
- ✓
Set the NAT IP allocation to manual
- ✗
Enable logging on the NAT gateway
Why it's wrong here
Logging helps monitoring but does not prevent port exhaustion.
- ✗
Enable endpoint-independent mapping
Why it's wrong here
This is a UDP optimization, not for port exhaustion prevention.
- ✓
Set the maximum ports per VM to a reasonable value
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
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.
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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Implementing VPC Instances — study guide chapter
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FAQ
Questions learners often ask
What does this PCNE question test?
Implementing VPC Instances — This question tests Implementing VPC Instances — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: Set the minimum ports per VM to a reasonable value — To prevent port exhaustion, the engineer should enable manual port allocation to set limits, configure endpoint-independent mapping for UDP (not directly related to port exhaustion), and set a minimum ports per VM to guarantee each VM gets a baseline. Manual allocation allows setting a maximum number of ports per VM, which prevents a single VM from using all ports.
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.
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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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