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 have a pod that is CrashLoopBackOff. The logs show 'error: dial tcp: lookup service.default.svc.cluster.local: no such host'. 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.
Why wrong: While CoreDNS being down could cause this, the error is about a specific service name not found, not a generic DNS failure. More likely the service doesn't exist.
C
The pod's DNS policy is set to 'None'
Why wrong: If DNS policy was None, the pod would not even attempt cluster DNS; the error shows it tried but failed.
D
A network policy is blocking UDP port 53
Why wrong: Network policies block traffic; but DNS would likely timeout or connection refused, not 'no such host'.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The service 'service' does not exist in the 'default' namespace
The error message 'no such host' indicates that the DNS lookup for 'service.default.svc.cluster.local' failed because the hostname does not exist. In Kubernetes, this FQDN resolves only if a Service named 'service' exists in the 'default' namespace. Since the lookup fails with 'no such host', the most likely cause is that the Service does not exist, not a DNS infrastructure issue.
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 CoreDNS pod is down
Why it's wrong here
While CoreDNS being down could cause this, the error is about a specific service name not found, not a generic DNS failure. More likely the service doesn't exist.
✗
The pod's DNS policy is set to 'None'
Why it's wrong here
If DNS policy was None, the pod would not even attempt cluster DNS; the error shows it tried but failed.
✗
A network policy is blocking UDP port 53
Why it's wrong here
Network policies block traffic; but DNS would likely timeout or connection refused, not 'no such host'.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The CKA exam frequently reuses these exact scenarios with slightly different constraints.
✓The service 'service' does not exist in the 'default' namespaceCorrect answer▾✗The CoreDNS pod is downWrong answer — click to see why▾
Why this is wrong here
While CoreDNS being down could cause this, the error is about a specific service name not found, not a generic DNS failure. More likely the service doesn't exist.
✗The pod's DNS policy is set to 'None'Wrong answer — click to see why▾
Why this is wrong here
If DNS policy was None, the pod would not even attempt cluster DNS; the error shows it tried but failed.
✗A network policy is blocking UDP port 53Wrong answer — click to see why▾
Why this is wrong here
Network policies block traffic; but DNS would likely timeout or connection refused, not 'no such host'.
Analysis generated from the official CKAblueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often assume any DNS error means CoreDNS is down, but the specific 'no such host' message points to a missing DNS record, not a DNS service failure.
Trap categories for this question
Command / output trap
If DNS policy was None, the pod would not even attempt cluster DNS; the error shows it tried but failed.
Detailed technical explanation
How to think about this question
Kubernetes DNS resolution for Services follows the pattern <service-name>.<namespace>.svc.cluster.local. When a pod attempts to resolve this FQDN, the cluster DNS (CoreDNS) returns an NXDOMAIN response if the Service does not exist in the specified namespace. This is different from a DNS server being unreachable, which would produce a timeout or SERVFAIL. The 'no such host' error in Go's net package maps directly to a DNS NXDOMAIN response, confirming the record is missing.
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 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.
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 service 'service' does not exist in the 'default' namespace — The error message 'no such host' indicates that the DNS lookup for 'service.default.svc.cluster.local' failed because the hostname does not exist. In Kubernetes, this FQDN resolves only if a Service named 'service' exists in the 'default' namespace. Since the lookup fails with 'no such host', the most likely cause is that the Service does not exist, not a DNS infrastructure issue.
What should I do if I get this CKA 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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