This CKAD practice question tests your understanding of services and networking. 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 create a Service named 'backend' in namespace 'prod'. A pod in namespace 'dev' tries to reach the service using the DNS name 'backend.prod.svc.cluster.local'. The pod cannot resolve the name. 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 pod is using the short name 'backend' without the namespace suffix
By default, Kubernetes DNS resolves names within the same namespace. To resolve across namespaces, the fully qualified domain name (FQDN) must be used. Option B is correct. Option A is incorrect because cluster DNS is enabled by default. Option C is incorrect because CoreDNS can resolve cross-namespace requests if the FQDN is used. Option D is incorrect because namespace deletion would remove the service entirely.
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.
✗
CoreDNS is configured to reject cross-namespace queries
Why it's wrong here
By default, CoreDNS allows queries for any namespace as long as the FQDN is used.
✗
The 'prod' namespace does not exist
Why it's wrong here
If the namespace didn't exist, the service would not exist either, but the DNS query would return NXDOMAIN.
✓
The pod is using the short name 'backend' without the namespace suffix
Why this is correct
Pods can only resolve short service names within the same namespace. To resolve a service in another namespace, the FQDN must be used.
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 cluster DNS service is not running
Why it's wrong here
If cluster DNS were not running, no DNS resolution would work at all, not just cross-namespace.
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 CKAD 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 CKAD question in full detail.
Identify which CKAD 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.
Services and Networking — This question tests Services and Networking — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The pod is using the short name 'backend' without the namespace suffix — By default, Kubernetes DNS resolves names within the same namespace. To resolve across namespaces, the fully qualified domain name (FQDN) must be used. Option B is correct. Option A is incorrect because cluster DNS is enabled by default. Option C is incorrect because CoreDNS can resolve cross-namespace requests if the FQDN is used. Option D is incorrect because namespace deletion would remove the service entirely.
What should I do if I get this CKAD question wrong?
Identify which CKAD 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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Question Discussion
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