This CKAD practice question tests your understanding of services and networking. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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 DevOps engineer notices that traffic to a Service named 'api' is not being forwarded to newly created pods. The Service selects pods with label 'app: api'. The pods are running and have the correct label. However, the Service's endpoints list does not include the new pods. 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.
The pods are in a different namespace
Why wrong: Services only select pods in the same namespace.
The Service's targetPort does not match the container's port
If targetPort does not match, endpoints are not created.
The Service type is NodePort instead of ClusterIP
Why wrong: Service type does not affect endpoint creation.
The pods have a different label than 'app: api'
Why wrong: The engineer noted the pods have the correct label.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
The Service's targetPort does not match the container's port
Option B is correct because the Service's `targetPort` must match the `containerPort` defined in the pod's container spec. If they differ, the Service will not route traffic to the pod, and the pod will not appear in the Endpoints object, even if the label selector matches. Kubernetes validates the endpoint population by checking that the pod's readiness probe passes and that the target port is reachable on the pod's IP.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
The pods are in a different namespace
Why it's wrong here
Services only select pods in the same namespace.
The Service's targetPort does not match the container's port
Why this is correct
If targetPort does not match, endpoints are not created.
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 Service type is NodePort instead of ClusterIP
Why it's wrong here
Service type does not affect endpoint creation.
The pods have a different label than 'app: api'
Why it's wrong here
The engineer noted the pods have the correct label.
Common exam traps
CNCF often tests the subtle distinction between the Service's `port` (exposed by the Service) and `targetPort` (the container's listening port), where candidates assume the `port` field is used for pod selection, leading them to overlook the `targetPort` mismatch.
Detailed technical explanation
Under the hood, the Kubernetes controller-manager's endpoint controller watches pods matching the Service's selector and creates EndpointSlices (or Endpoints) only when the pod's `containerPort` matches the Service's `targetPort`. If `targetPort` is omitted, it defaults to the `port` field, which can cause mismatches if the container listens on a different port. In real-world scenarios, this often happens when a pod is updated to expose a new port but the Service definition is not updated accordingly.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
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.
What to study next
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FAQ
Services and Networking — This question tests Services and Networking — Read the scenario before looking for a memorised answer..
The correct answer is: The Service's targetPort does not match the container's port — Option B is correct because the Service's `targetPort` must match the `containerPort` defined in the pod's container spec. If they differ, the Service will not route traffic to the pod, and the pod will not appear in the Endpoints object, even if the label selector matches. Kubernetes validates the endpoint population by checking that the pod's readiness probe passes and that the target port is reachable on the pod's IP.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 30, 2026
This CKAD practice question is part of Courseiva's free CNCF 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 CKAD exam.
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