PCSE Configuring network security Practice Question
This PCSE practice question tests your understanding of configuring network security. 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.
A company has a VPC with a subnet (10.1.0.0/24) in us-central1. They have a Cloud NAT configured for outbound traffic to the internet. They want instances in this subnet to access a third-party API that is only accessible over the internet and requires a specific static source IP for whitelisting. What is the recommended approach?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Reserve a static NAT IP in Cloud NAT and whitelist that IP with the third party.
Cloud NAT allows instances without external IPs to initiate outbound connections to the internet. By reserving a static NAT IP address in Cloud NAT, you ensure all outbound traffic from the subnet uses a consistent source IP, which can be whitelisted by the third-party API. This meets the requirement for a static source IP without assigning external IPs to individual instances.
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.
✗
Assign external IPs to the instances and use network-level access controls.
Why it's wrong here
Assigning external IPs reduces security and may not provide a static IP for whitelisting.
✗
Use Private Google Access to route traffic through Google's network.
Why it's wrong here
Private Google Access applies only to Google APIs and services, not third-party APIs.
✓
Reserve a static NAT IP in Cloud NAT and whitelist that IP with the third party.
Why this is correct
Cloud NAT can use a static external IP that is consistent and can be whitelisted.
Related concept
Read the scenario before looking for a memorised answer.
✗
Configure a VPC Service Controls perimeter to restrict egress.
Why it's wrong here
VPC Service Controls protect Google-managed services, not third-party APIs.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates may confuse Private Google Access (which only works for Google APIs) with general internet egress, or assume that assigning ephemeral external IPs is sufficient for static whitelisting, ignoring that ephemeral IPs can change on instance restart or stop/start.
Detailed technical explanation
How to think about this question
Cloud NAT uses Source Network Address Translation (SNAT) to map private IPs of instances to a single public IP (or a pool). When you reserve a static NAT IP, it is allocated from the regional external IP address pool and remains fixed even if the Cloud NAT gateway is recreated. This ensures that the third-party API sees a consistent source IP, which is critical for IP-based whitelisting. Under the hood, Cloud NAT is implemented as a managed service using Google's Andromeda virtual network stack, handling connection tracking and port allocation automatically.
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
A company's IT admin needs to give a contractor read-only access to production logs without sharing account credentials. Using role-based access control (RBAC) and temporary scoped permissions — not a permanent shared password — is the correct pattern. Questions like this test whether you can apply least-privilege access across cloud identity services.
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: Reserve a static NAT IP in Cloud NAT and whitelist that IP with the third party. — Cloud NAT allows instances without external IPs to initiate outbound connections to the internet. By reserving a static NAT IP address in Cloud NAT, you ensure all outbound traffic from the subnet uses a consistent source IP, which can be whitelisted by the third-party API. This meets the requirement for a static source IP without assigning external IPs to individual instances.
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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