The answer is that to allow HTTP traffic from the internet to a VM instance, you must both assign an external (public) IP address to the VM and create a firewall rule allowing ingress on TCP port 80 from 0.0.0.0/0. An external IP is the fundamental requirement for direct internet reachability because, without it, the VM resides entirely within the private VPC network and cannot receive unsolicited inbound traffic from outside, regardless of firewall rules. The firewall rule then explicitly permits the HTTP traffic to reach the VM’s network interface. On the Google Professional Cloud Network Engineer exam, this pairing tests your understanding that security groups and routing are secondary to the VM’s public-facing address—a common trap is assuming a firewall rule alone suffices. Remember the memory tip: “IP first, then firewall” to avoid missing the external IP requirement when configuring internet access.
PCNE Implementing a Virtual Private Cloud Practice Question
This PCNE practice question tests your understanding of implementing a virtual private cloud. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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 has a VPC with a subnet in us-central1 and needs to allow HTTP traffic (port 80) from the internet to a VM instance. Which TWO configurations are required?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Assign an external IP address to the VM.
Option B is correct because a VM must have an external (public) IP address assigned to be directly reachable from the internet. Without an external IP, the VM cannot receive inbound traffic initiated from outside the VPC, even with proper firewall rules. This is a fundamental requirement for internet-facing workloads in Google Cloud.
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.
✗
Configure Cloud NAT for the VPC.
Why it's wrong here
Cloud NAT provides outbound internet, not inbound.
✓
Assign an external IP address to the VM.
Why this is correct
An external IP allows the VM to be reachable from the internet.
Related concept
Read the scenario before looking for a memorised answer.
✗
Enable Private Google Access on the subnet.
Why it's wrong here
Private Google Access is for accessing Google APIs, not for general internet inbound.
✗
Assign a static internal IP address to the VM.
Why it's wrong here
Internal IP is not needed for inbound internet access.
✓
Create a firewall rule to allow ingress on TCP port 80 from 0.0.0.0/0.
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Google Cloud often tests the misconception that Cloud NAT or Private Google Access can substitute for an external IP when allowing inbound internet traffic, but these services only support outbound or API-specific connectivity, not inbound internet access.
Detailed technical explanation
How to think about this question
When a VM has an external IP, Google Cloud's Andromeda software-defined networking performs 1:1 NAT, mapping the external IP to the VM's internal IP. The firewall rule allowing ingress on TCP port 80 from 0.0.0.0/0 must be created with a target tag or service account to apply to the VM; without it, the default deny-all ingress rule blocks the traffic. In a real-world scenario, you might also use a load balancer to front-end the VM, which would handle external IP assignment and firewall rules differently.
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 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.
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: Assign an external IP address to the VM. — Option B is correct because a VM must have an external (public) IP address assigned to be directly reachable from the internet. Without an external IP, the VM cannot receive inbound traffic initiated from outside the VPC, even with proper firewall rules. This is a fundamental requirement for internet-facing workloads in Google Cloud.
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.
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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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