KCNA Container Orchestration Practice Question
A DevOps team notices that a new deployment of a web application is not receiving traffic even though the pods are running. The deployment has a selector matching the pod labels, and a Service of type ClusterIP exists. What is the most likely cause?
⚠ Common exam trap
Many candidates confuse the Service's `port` (the port the Service listens on) with `targetPort` (the port on the pod), assuming they must match, or they incorrectly attribute the issue to missing readiness probes or Ingress resources.
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 Service's targetPort does not match the container's containerPort.
The most likely cause is that the Service's targetPort does not match the container's containerPort. In Kubernetes, a Service routes traffic to pods by forwarding packets to the port specified in the Service's `targetPort` field. If this does not match the `containerPort` defined in the pod's container spec, the traffic will be dropped because the kube-proxy will forward packets to a closed port on the pod, resulting in no connectivity even though the pods are running.
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's targetPort does not match the container's containerPort.
Why this is correct
The Service routes traffic to the targetPort, which must match the port the container listens on.
- ✗
The pods do not have a readiness probe defined.
Why it's wrong here
Readiness probes affect traffic routing only when pods are not ready, but the pods are running.
- ✗
The Service type should be NodePort to receive traffic.
Why it's wrong here
ClusterIP is sufficient for internal traffic.
- ✗
The Service is not exposed via an Ingress.
Why it's wrong here
Ingress is for external HTTP traffic, not required for internal ClusterIP.
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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.