The answer is that the record 'myapp.example.internal' does not exist in the private zone. This is the most likely cause because Cloud DNS returns an NXDOMAIN response only when the queried record name is absent from the zone, even if the zone itself is correctly attached to the VPC. Since the question confirms the private zone for 'example.internal' is attached, the resolution failure points directly to a missing A record for 'myapp'. On the Google Professional Cloud Network Engineer exam, this scenario tests your understanding that private DNS zone resolution failure is almost never a zone attachment issue when the zone is confirmed attached—the trap is assuming a network or peering problem when the real culprit is an undefined record. Remember the mnemonic: "Zone attached, record detached" to quickly recall that NXDOMAIN means the record itself is missing, not the zone.
PCNE Configuring network services Practice Question
This PCNE practice question tests your understanding of configuring network services. 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 is using Cloud DNS for private zone resolution within their VPC. They have a private zone for 'example.internal' and have attached it to the VPC. When they create a new Compute Engine VM and try to resolve 'myapp.example.internal', it fails. 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 record 'myapp.example.internal' does not exist in the zone
Option D is correct because the most likely cause of a resolution failure for a specific record is that the record does not exist in the private zone. The question states the zone is attached to the VPC, so the zone itself is accessible; the failure is specific to the record name. Cloud DNS will return an NXDOMAIN response if the record is not defined, even if the zone is properly configured.
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 private zone is not attached to the VPC
Why it's wrong here
The stem says it is attached.
✗
The VM's /etc/resolv.conf does not point to Cloud DNS
Why it's wrong here
VMs in a VPC automatically use the internal DNS resolver.
✗
Firewall rule blocking DNS traffic (UDP 53) to the metadata server
Why it's wrong here
DNS queries go to metadata server (169.254.169.254) which is not blocked by default.
✓
The record 'myapp.example.internal' does not exist in the zone
Why this is correct
Private zone is authoritative; records must be added explicitly.
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.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Google Cloud often tests the misconception that DNS failures in a private zone are due to firewall rules or resolver configuration, when in fact the metadata server handles DNS transparently and the most common cause is a missing DNS record.
Detailed technical explanation
How to think about this question
Cloud DNS private zones use the metadata server (169.254.169.254) as a DNS resolver, which forwards queries to the Cloud DNS backend. The metadata server handles DNS on a special internal interface that bypasses VPC firewall rules, so firewall misconfigurations rarely cause resolution failures for private zones. A common real-world scenario is when a record is misspelled or not yet created, leading to an NXDOMAIN response that is indistinguishable from a zone misconfiguration to the user.
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.
Configuring network services — This question tests Configuring network services — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The record 'myapp.example.internal' does not exist in the zone — Option D is correct because the most likely cause of a resolution failure for a specific record is that the record does not exist in the private zone. The question states the zone is attached to the VPC, so the zone itself is accessible; the failure is specific to the record name. Cloud DNS will return an NXDOMAIN response if the record is not defined, even if the zone is properly configured.
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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Question Discussion
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