- A
Place web servers in a public subnet with external IPs, database in a private subnet, and add a firewall rule allowing traffic from web subnet to database
This design provides proper segmentation and security.
- B
Place both tiers in separate VPCs and use VPC peering with no firewall rules
Why wrong: VPC peering without firewall rules allows all traffic between VPCs, not restricted to database access only.
- C
Place both tiers in the same subnet and configure firewall rules to restrict database access
Why wrong: Placing both in same subnet does not provide network segmentation; firewall rules alone can restrict, but best practice is separate subnets.
- D
Place web servers in a private subnet with Cloud NAT for outbound, database in the same private subnet
Why wrong: Web servers would not be directly accessible from internet; Cloud NAT is for outbound only.
PCNE Practice Question: Designing, planning, and prototyping a GCP network
This PCNE practice question tests your understanding of designing, planning, and prototyping a gcp network. 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 startup is migrating a two-tier application to GCP. The web tier must be accessible from the internet, and the database tier must only be accessible from the web tier. Which network design should be used?
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
Place web servers in a public subnet with external IPs, database in a private subnet, and add a firewall rule allowing traffic from web subnet to database
Option A is correct because it places the web servers in a public subnet with external IPs, allowing direct internet access, while the database resides in a private subnet with no external IP, enforcing isolation. A firewall rule (ingress on the database subnet) explicitly permits traffic from the web subnet’s CIDR range, typically on the database port (e.g., TCP 3306 for MySQL), ensuring the database is reachable only from the web tier. This design follows GCP’s best practice of using VPC firewall rules to control east-west traffic between subnets.
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.
- ✓
Place web servers in a public subnet with external IPs, database in a private subnet, and add a firewall rule allowing traffic from web subnet to database
Why this is correct
This design provides proper segmentation and security.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Place both tiers in separate VPCs and use VPC peering with no firewall rules
Why it's wrong here
VPC peering without firewall rules allows all traffic between VPCs, not restricted to database access only.
- ✗
Place both tiers in the same subnet and configure firewall rules to restrict database access
Why it's wrong here
Placing both in same subnet does not provide network segmentation; firewall rules alone can restrict, but best practice is separate subnets.
- ✗
Place web servers in a private subnet with Cloud NAT for outbound, database in the same private subnet
Why it's wrong here
Web servers would not be directly accessible from internet; Cloud NAT is for outbound only.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Google Cloud often tests the misconception that placing resources in the same subnet automatically allows isolation via firewall rules, but in GCP, firewall rules are applied at the instance level (via tags or service accounts) and cannot restrict traffic between instances in the same subnet without additional tagging, leading candidates to incorrectly choose Option C.
Detailed technical explanation
How to think about this question
Under the hood, GCP VPC firewall rules are stateful and evaluated on a per-instance basis using network tags or service accounts, not just subnet CIDRs. In a multi-tier design, you can use network tags (e.g., 'web' and 'db') to create a firewall rule that allows ingress to instances tagged 'db' only from instances tagged 'web', providing granular control even within the same subnet. A real-world scenario where this matters is when using managed instance groups for auto-scaling; the firewall rule must match the tags applied by the instance template to ensure new instances inherit the correct access controls.
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 media company stores terabytes of video archives that are accessed once a year for audit purposes. Moving these objects to a cold storage tier (Azure Archive, S3 Glacier, or Google Nearline) costs a fraction of hot storage. Questions like this test whether you understand storage tiers, access frequency tradeoffs, and retrieval latency requirements.
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.
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FAQ
Questions learners often ask
What does this PCNE question test?
Designing, planning, and prototyping a GCP network — This question tests Designing, planning, and prototyping a GCP network — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Place web servers in a public subnet with external IPs, database in a private subnet, and add a firewall rule allowing traffic from web subnet to database — Option A is correct because it places the web servers in a public subnet with external IPs, allowing direct internet access, while the database resides in a private subnet with no external IP, enforcing isolation. A firewall rule (ingress on the database subnet) explicitly permits traffic from the web subnet’s CIDR range, typically on the database port (e.g., TCP 3306 for MySQL), ensuring the database is reachable only from the web tier. This design follows GCP’s best practice of using VPC firewall rules to control east-west traffic between subnets.
What should I do if I get this PCNE 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.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Last reviewed: Jun 30, 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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