CKA Practice Question: Cluster Architecture, Installation and Configuration
This CKA practice question tests your understanding of cluster architecture, installation and configuration. 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.
A pod is stuck in 'Pending' state. 'kubectl describe pod' shows '0/1 nodes are available: 1 node(s) had taint {node.kubernetes.io/unreachable: }, that the pod didn't tolerate'. What does this indicate?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The node is not reachable by the control plane
The error message indicates that the node has a taint of `node.kubernetes.io/unreachable`, which is automatically added by the node controller when the control plane cannot communicate with the node (e.g., due to network failure or kubelet being down). The pod remains in 'Pending' because no node is available that tolerates this taint, meaning the node is unreachable from the control plane. This matches option C.
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.
✗
The pod has been successfully scheduled to the node
Why it's wrong here
The pod is pending, not scheduled.
✗
The node has insufficient resources and is tainted
Why it's wrong here
Resource shortages cause 'Insufficient cpu/memory', not 'unreachable' taint.
✓
The node is not reachable by the control plane
Why this is correct
The 'unreachable' taint indicates the node controller has lost contact with the node.
Related concept
Read the scenario before looking for a memorised answer.
✗
The node does not exist
Why it's wrong here
The node exists but is unreachable; the taint is applied by the node controller.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse taints related to resource pressure (like memory or disk) with the unreachable taint, or assume 'Pending' means the pod is scheduled but waiting for resources, when in fact the specific taint name directly indicates a node reachability issue.
Detailed technical explanation
How to think about this question
The `node.kubernetes.io/unreachable` taint is set by the `node-lifecycle-controller` when the node has been unreachable for a period (default 40 seconds, based on the `node-monitor-grace-period`). This triggers pod eviction after a `pod-eviction-timeout` (default 5 minutes). In a real-world scenario, this could occur during a network partition or if the kubelet process crashes, and operators must check node status with `kubectl get nodes` and investigate logs on the node or control plane.
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.
TExam Day Tips
→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 CKA 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 CKA question in full detail.
Cluster Architecture, Installation and Configuration — This question tests Cluster Architecture, Installation and Configuration — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The node is not reachable by the control plane — The error message indicates that the node has a taint of `node.kubernetes.io/unreachable`, which is automatically added by the node controller when the control plane cannot communicate with the node (e.g., due to network failure or kubelet being down). The pod remains in 'Pending' because no node is available that tolerates this taint, meaning the node is unreachable from the control plane. This matches option C.
What should I do if I get this CKA question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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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