CKA Services and Networking Practice Question
You have three pods selected by a service. One pod is in 'CrashLoopBackOff' state. How does the service's endpoints behave?
⚠ Common exam trap
CNCF often tests the misconception that a service will still include an unhealthy pod in its endpoints but simply not route traffic to it, whereas in reality the endpoint controller removes the pod entirely from the endpoint list based on readiness probe failures.
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 endpoints include only the two healthy pods
B is correct because Kubernetes services use endpoints (or endpoint slices) to track which pods are ready to receive traffic. The readiness probe determines pod readiness; a pod in CrashLoopBackOff fails its readiness probe, so it is removed from the service's endpoints. Only the two healthy pods remain in the endpoint list, ensuring traffic is routed only to healthy pods.
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 removes all endpoints to avoid partial connectivity
Why it's wrong here
The Service does not remove all endpoints when one Pod fails; that would needlessly drop the two healthy endpoints and cause a total loss of connectivity. Instead, the Endpoints controller removes only the IP of the Pod that has failed its readiness probe, preserving the remaining ready Pods as valid traffic destinations.
- ✓
The service endpoints include only the two healthy pods
Why this is correct
The Endpoints object for a Service contains only the IP addresses of Pods that are currently Ready — that is, passing their readiness probes. Since two of the three Pods are healthy, the Service's Endpoints (or EndpointSlices) list exactly those two Pod IPs, and the ClusterIP load balances only to them.
- ✗
The service endpoints include the unhealthy pod but traffic is not routed to it
Why it's wrong here
This is incorrect because an unhealthy Pod is not kept in the Endpoints object while traffic 'skips' it; the Endpoints controller actively deletes the failed Pod's IP from the endpoint list. Once removed, the Pod can never receive Service traffic because it is no longer a target, so the statement misrepresents the underlying endpoint pruning behavior.
- ✗
The service includes all three pods in its endpoints
Why it's wrong here
This would only be true if all three Pods were Ready, but the unhealthy Pod has a failing readiness probe. Because readiness gates the endpoint population, only the two healthy Pod addresses are present, so the Service does not include the failed Pod at all.
Go deeper
Related to this question
Learn chapter
Kubernetes Architecture Overview
Key term
Pod Failure Troubleshooting
Pod failure troubleshooting is the process of identifying and resolving issues that cause Kubernetes pods to crash, restart, or become unavailable.
Key term
Network Policies
A Kubernetes resource that controls how pods communicate with each other and with other network endpoints, acting as a firewall for pod-to-pod traffic.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This CKA 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 CKA exam.