This CKA practice question tests your understanding of troubleshooting. 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.
You are troubleshooting a DNS issue in the cluster. You exec into a pod and run 'nslookup kubernetes.default.svc.cluster.local'. The command returns 'server can't find kubernetes.default.svc.cluster.local: NXDOMAIN'. 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 CoreDNS pod(s) are not running or are misconfigured
Option C is correct. NXDOMAIN indicates that the DNS server does not have a record for that name. The most common cause is that the CoreDNS pod(s) are not running or are misconfigured. Option A would cause a timeout not NXDOMAIN. Option B would cause a different error (connection refused). Option D might cause partial resolution but not NXDOMAIN for the entire service name.
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 kube-dns service does not exist
Why it's wrong here
If the service does not exist, nslookup would return a 'connection refused' or 'server failure' error, not NXDOMAIN.
✗
The pod's /etc/resolv.conf points to an external DNS server instead of the cluster DNS
Why it's wrong here
If it points to an external server, the query would likely succeed or timeout, but not return NXDOMAIN for the cluster domain.
✓
The CoreDNS pod(s) are not running or are misconfigured
Why this is correct
If CoreDNS is down, DNS resolution fails with NXDOMAIN because there is no server to answer.
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 pod's network policy blocks DNS traffic
Why it's wrong here
Network policies typically drop packets, causing timeouts rather than NXDOMAIN.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Detailed technical explanation
How to think about this question
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
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.
Use explanations to understand the rule behind the answer.
TExam Day Tips
→Underline the problem statement mentally.
→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 practitioner preparing for the CKA exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this CKA question in full detail.
Identify which CKA exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
Troubleshooting — This question tests Troubleshooting — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The CoreDNS pod(s) are not running or are misconfigured — Option C is correct. NXDOMAIN indicates that the DNS server does not have a record for that name. The most common cause is that the CoreDNS pod(s) are not running or are misconfigured. Option A would cause a timeout not NXDOMAIN. Option B would cause a different error (connection refused). Option D might cause partial resolution but not NXDOMAIN for the entire service name.
What should I do if I get this CKA question wrong?
Identify which CKA exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
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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