KCNA Container Orchestration Practice Question
A user creates a Service of type ClusterIP with a selector matching pods labeled 'app: myapp'. However, a pod named 'myapp-pod' with label 'app: myapp' is not receiving traffic. What is a possible reason?
⚠ Common exam trap
The CNCF-KCNA exam often tests the distinction between liveness and readiness probes; the trap here is that candidates assume a running pod automatically receives traffic, overlooking that readiness probes explicitly gate traffic admission.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The pod's readiness probe is failing
A failing readiness probe causes the pod to be removed from the Service's Endpoints list, even if the pod is running and matches the selector. The kubelet checks the readiness probe periodically; if it fails, the pod is marked as not ready, and the Service controller removes its IP from the Endpoints object, preventing traffic from being forwarded to it.
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 Service type should be NodePort
Why it's wrong here
Type ClusterIP works within the cluster.
- ✗
The pod is in a different namespace
Why it's wrong here
Services only select pods in the same namespace.
- ✓
The pod's readiness probe is failing
Why this is correct
Services only forward traffic to pods that pass readiness probes.
- ✗
The pod's container port is not defined
Why it's wrong here
The Service targetPort must match the container port, but missing container port would not prevent traffic if targetPort matches.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This KCNA 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 KCNA exam.