PCNE Practice Question: Designing, Planning, and Prototyping a GCP Network
A company has Compute Engine instances without external IPs that need to access the internet for updates. They do not want any inbound traffic. What is the best design?
⚠ Common exam trap
Test-takers frequently assume default firewall rules are sufficient for security, but they actually allow some ingress (e.g., ICMP from internal ranges), so a deny-all-ingress rule is necessary to fully block inbound traffic.
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
✓
Configure Cloud NAT and add firewall rules to allow only necessary egress and deny all ingress.
Cloud NAT provides outbound internet connectivity for instances without external IPs, and the explicit firewall rules ensure only necessary egress traffic is allowed while denying all ingress, meeting the requirement of no inbound traffic. Default firewall rules allow some ingress (e.g., ICMP), so they must be overridden with a deny-all-ingress rule to fully block inbound traffic.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Configure Cloud NAT and rely on default firewall rules.
Why it's wrong here
Default rules allow inbound from inside VPC, not secure.
- ✓
Configure Cloud NAT and add firewall rules to allow only necessary egress and deny all ingress.
Why this is correct
Meets both outbound access and inbound blocking requirements.
- ✗
Configure Cloud NAT and add a firewall rule to allow all egress traffic.
Why it's wrong here
Allows all egress but does not explicitly block inbound.
- ✗
Configure Cloud NAT and add a firewall rule to deny all ingress and egress.
Why it's wrong here
Denies outbound traffic, preventing updates.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.