- A
Create an egress allow rule for the specific package sources and a deny all egress rule with lower priority (higher number).
Correct: The allow rule matches the specific destinations, and the deny all rule with lower priority (higher number) catches everything else. Because VPC firewall rules are evaluated from highest to lowest priority, the allow rule first permits the desired traffic, then the deny rule blocks the rest.
- B
Create an egress deny rule for all traffic and then a higher-priority allow rule for the package sources.
Why wrong: If a deny all rule is higher priority (lower number), it will override the allow rule for the package sources, blocking all egress.
- C
Create an ingress allow rule for the package sources and a deny all egress rule with higher priority.
Why wrong: Ingress rules control incoming traffic, not outbound. The requirement is for egress traffic.
- D
Use Cloud NAT to force all egress through a single IP and then restrict with a firewall rule.
Why wrong: Cloud NAT provides outbound connectivity but does not filter traffic; it is used for NAT, not firewall filtering.
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 security engineer wants to allow egress traffic from Compute Engine instances to the internet only for updates to a specific set of packages. All other egress must be denied. Which VPC firewall rule configuration should the engineer use?
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 an egress allow rule for the specific package sources and a deny all egress rule with lower priority (higher number).
VPC firewall rules are stateful, so allowing egress for specific destinations (e.g., package repositories) automatically allows return traffic. Deny rules should be used to block all other egress. The correct approach is an egress allow rule for the specific destinations and a lower-priority egress deny rule for all other traffic.
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 an egress allow rule for the specific package sources and a deny all egress rule with lower priority (higher number).
Why this is correct
Correct: The allow rule matches the specific destinations, and the deny all rule with lower priority (higher number) catches everything else. Because VPC firewall rules are evaluated from highest to lowest priority, the allow rule first permits the desired traffic, then the deny rule blocks the rest.
Related concept
Static NAT maps one inside address to one outside address.
- ✗
Create an egress deny rule for all traffic and then a higher-priority allow rule for the package sources.
Why it's wrong here
If a deny all rule is higher priority (lower number), it will override the allow rule for the package sources, blocking all egress.
- ✗
Create an ingress allow rule for the package sources and a deny all egress rule with higher priority.
Why it's wrong here
Ingress rules control incoming traffic, not outbound. The requirement is for egress traffic.
- ✗
Use Cloud NAT to force all egress through a single IP and then restrict with a firewall rule.
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
An e-commerce site experiences heavy traffic on Black Friday and near-zero traffic during off-peak weeks. Rather than provisioning permanent large VMs, the team uses auto-scaling groups that add capacity automatically under load and reduce it overnight. Questions like this test whether you understand elasticity, availability zones, and cloud compute scaling patterns.
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 PCSE NAT questions on configuration and troubleshooting.
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Configuring Network Security — study guide chapter
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FAQ
Questions learners often ask
What does this PCSE question test?
Configuring Network Security — This question tests Configuring Network Security — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: Create an egress allow rule for the specific package sources and a deny all egress rule with lower priority (higher number). — VPC firewall rules are stateful, so allowing egress for specific destinations (e.g., package repositories) automatically allows return traffic. Deny rules should be used to block all other egress. The correct approach is an egress allow rule for the specific destinations and a lower-priority egress deny rule for all other traffic.
What should I do if I get this PCSE 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 PCSE NAT questions on configuration and troubleshooting.
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 PCSE 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 PCSE exam.
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