- A
Create a Cloud NAT and assign the application instances a static IP, then allow that IP in the on-premises firewall
Why wrong: This approach is less secure because any instance with that static IP could access the database, and it doesn't leverage GCP identity.
- B
Create a firewall egress rule with destination IP range of the on-premises database and source service account of the application instances
Using service accounts ensures only instances with that specific identity can access the database.
- C
Create a firewall egress rule with destination IP range of the on-premises database and source tags 'db-access'
Why wrong: Tags can be applied to any instance, leading to potential misuse; service accounts are more secure.
- D
Use VPC Service Controls to create a perimeter around the application VPC
Why wrong: VPC Service Controls protect managed services, not on-premises connectivity.
Google PCA Designing for Security and Compliance Practice Question
This PCA practice question tests your understanding of designing for security and compliance. 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 migrating an on-premises application to Google Cloud. The application requires access to a legacy database that can only be reached from a specific on-premises IP address. The company has established a Cloud VPN tunnel. What is the MOST secure way to ensure that only the migrated application's Compute Engine instances can initiate connections to the on-premises database?
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
Create a firewall egress rule with destination IP range of the on-premises database and source service account of the application instances
Using firewall rules with target service accounts allows you to control egress traffic based on the identity of the source instances, which is more secure than using tags or IP ranges.
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.
- ✗
Create a Cloud NAT and assign the application instances a static IP, then allow that IP in the on-premises firewall
Why it's wrong here
This approach is less secure because any instance with that static IP could access the database, and it doesn't leverage GCP identity.
- ✓
Create a firewall egress rule with destination IP range of the on-premises database and source service account of the application instances
Why this is correct
Using service accounts ensures only instances with that specific identity can access the database.
Related concept
Static NAT maps one inside address to one outside address.
- ✗
Create a firewall egress rule with destination IP range of the on-premises database and source tags 'db-access'
Why it's wrong here
Tags can be applied to any instance, leading to potential misuse; service accounts are more secure.
- ✗
Use VPC Service Controls to create a perimeter around the application VPC
Why it's wrong here
VPC Service Controls protect managed services, not on-premises connectivity.
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.
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 PCA NAT questions on configuration and troubleshooting.
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Designing for Security and Compliance — study guide chapter
Learn the concepts, then practise the questions
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FAQ
Questions learners often ask
What does this PCA question test?
Designing for Security and Compliance — This question tests Designing for Security and Compliance — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: Create a firewall egress rule with destination IP range of the on-premises database and source service account of the application instances — Using firewall rules with target service accounts allows you to control egress traffic based on the identity of the source instances, which is more secure than using tags or IP ranges.
What should I do if I get this PCA 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 PCA NAT questions on configuration and troubleshooting.
What is the key concept behind this question?
Static NAT maps one inside address to one outside address.
About these practice questions
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Last reviewed: Jul 4, 2026
This PCA 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 PCA exam.
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