The answer is the deny-all-egress firewall rule with the lowest priority (65535) that blocks all outbound traffic. This is correct because Google Cloud VPCs include an implicit default deny egress rule that blocks all outbound traffic not explicitly permitted by a higher-priority rule; since no rule allows outbound HTTPS on port 443, the VM’s requests are silently dropped. On the Google Professional Cloud Network Engineer exam, this tests your understanding of VPC firewall rule evaluation order and the often-overlooked default egress behavior—a common trap is assuming outbound traffic is allowed by default, when in fact only specific protocols like SSH or RDP are permitted via implied rules. Remember that in GCP, egress is denied by default unless you explicitly create a higher-priority allow rule; think of it as “deny all outbound, allow only what you write.” A useful memory tip: “Egress is a fortress—you must open the gate yourself.”
PCNE Implementing a Virtual Private Cloud Practice Question
This PCNE practice question tests your understanding of implementing a virtual private cloud. 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.
Refer to the exhibit. A VM in the my-vpc network is unable to reach an external HTTPS server. 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 the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The deny-all-egress firewall rule blocks all outbound traffic.
The default VPC configuration includes a deny-all-egress firewall rule with the lowest priority (65535) that blocks all outbound traffic not explicitly allowed. Since no higher-priority rule permits outbound traffic to the external HTTPS server (port 443), the VM's HTTPS requests are dropped by this implicit deny rule, preventing connectivity.
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.
✓
The deny-all-egress firewall rule blocks all outbound traffic.
Why this is correct
This egress deny rule with priority 1000 blocks all outbound traffic, including HTTPS.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
The allow-custom-internal rule only allows inbound traffic.
Why it's wrong here
While true, this rule does not affect outbound traffic; the issue is due to the egress deny rule.
✗
No rule allows outbound traffic to port 443.
Why it's wrong here
This is a consequence of the deny-all-egress rule, but the root cause is the deny rule itself.
✗
The default-allow-ssh rule has a low priority.
Why it's wrong here
Priority is unrelated to the outbound connectivity issue; the rule is for ingress SSH.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Google Cloud often tests the misconception that a missing allow rule is the direct cause, rather than recognizing the explicit deny-all-egress rule with lowest priority as the actual blocking mechanism.
Detailed technical explanation
How to think about this question
In Google Cloud VPC, firewall rules are stateful and evaluated in order of priority (lower number = higher priority). The implicit deny-all-egress rule (priority 65535) is always present unless overridden by a higher-priority allow rule. For HTTPS (TCP 443), a rule must explicitly allow egress traffic with destination 0.0.0.0/0 and protocol tcp:443; otherwise, the implicit deny drops the packets. This behavior is similar to AWS security groups' default deny-all-egress but with explicit priority-based evaluation.
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
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.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Implementing a Virtual Private Cloud — This question tests Implementing a Virtual Private Cloud — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The deny-all-egress firewall rule blocks all outbound traffic. — The default VPC configuration includes a deny-all-egress firewall rule with the lowest priority (65535) that blocks all outbound traffic not explicitly allowed. Since no higher-priority rule permits outbound traffic to the external HTTPS server (port 443), the VM's HTTPS requests are dropped by this implicit deny rule, preventing connectivity.
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.
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?
Read the scenario before looking for a memorised answer.
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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.
Question Discussion
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