- A
The instances have external IP addresses assigned.
Instances with external IPs do not use Cloud NAT; they directly connect using their external IP.
- B
The Cloud Router is not configured correctly.
Why wrong: Cloud Router is used for dynamic routing, but Cloud NAT uses a Cloud Router for NAT gateway configuration. Misconfiguration could cause issues, but the most common reason is external IPs.
- C
The firewall rules block egress traffic.
Why wrong: Firewall rules could block traffic, but the question states 'not being NATed' rather than blocked.
- D
The instances are in a different region than the Cloud NAT gateway.
Why wrong: Cloud NAT is regional; if instances are in a different region, they wouldn't use that NAT, but the question implies they are in the same region.
Google ACE Configuring Access and Security Practice Question
This ACE practice question tests your understanding of configuring access and security. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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 Cloud NAT to allow private Compute Engine instances to access the internet. They notice that traffic from some instances is not being NATed. What is the most likely cause?
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.
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 instances have external IP addresses assigned.
Cloud NAT only applies to instances that do not have external IP addresses. If an instance has an external IP, it will use that IP for outbound traffic and bypass Cloud NAT.
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
The instances have external IP addresses assigned.
- ✗
The Cloud Router is not configured correctly.
- ✗
The firewall rules block egress traffic.
Why it's wrong here
Firewall rules could block traffic, but the question states 'not being NATed' rather than blocked.
- ✗
The instances are in a different region than the Cloud NAT gateway.
Why it's wrong here
Cloud NAT is regional; if instances are in a different region, they wouldn't use that NAT, but the question implies they are in the same region.
Common exam traps
Common exam trap: NAT rules depend on direction and matching traffic
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Detailed technical explanation
How to think about this question
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
KKey Concepts to Remember
- Static NAT maps one inside address to one outside address.
- PAT allows many inside hosts to share one public address using ports.
- Inside local and inside global describe the private and translated addresses.
- NAT ACLs identify traffic for translation, not always security filtering.
TExam Day Tips
- Identify inside and outside interfaces first.
- Check whether the scenario needs static NAT, dynamic NAT or PAT.
- Do not confuse NAT matching ACLs with normal packet-filtering intent.
Key takeaway
NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
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.
Visual reference
What to study next
Got this wrong? Here's your next step.
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related ACE NAT questions on configuration and troubleshooting.
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Configuring Access and Security — study guide chapter
Learn the concepts, then practise the questions
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FAQ
Questions learners often ask
What does this ACE question test?
Configuring Access and Security — This question tests Configuring Access and Security — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: The instances have external IP addresses assigned. — Cloud NAT only applies to instances that do not have external IP addresses. If an instance has an external IP, it will use that IP for outbound traffic and bypass Cloud NAT.
What should I do if I get this ACE question wrong?
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related ACE NAT questions on configuration and troubleshooting.
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?
Static NAT maps one inside address to one outside address.
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Last reviewed: Jul 4, 2026
This ACE 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 ACE exam.
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