This KCNA practice question tests your understanding of kubernetes fundamentals. 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 '0/4 nodes are available: 4 node(s) had taint {node.kubernetes.io/unreachable: }, that the pod didn't tolerate.' 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.
All nodes have disk pressure.
Why wrong: The taint is 'unreachable', not 'disk-pressure'.
All nodes are unreachable or have been cordoned.
The taint indicates nodes are unreachable.
The pod has a toleration that matches the taint.
Why wrong: The error says 'didn't tolerate'.
The nodes do not have enough CPU or memory.
Why wrong: Resource constraints show different messages.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
All nodes are unreachable or have been cordoned.
The taint `node.kubernetes.io/unreachable` is automatically added by the node controller when a node becomes unreachable (e.g., network failure, kubelet stops heartbeating). The error shows all 4 nodes have this taint and the pod has no matching toleration, meaning the scheduler cannot place the pod. This directly indicates all nodes are unreachable or have been cordoned (which also adds the `node.kubernetes.io/unschedulable` taint, but here the specific taint is `unreachable`).
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.
All nodes have disk pressure.
Why it's wrong here
The taint is 'unreachable', not 'disk-pressure'.
All nodes are unreachable or have been cordoned.
Why this is correct
The taint indicates nodes are unreachable.
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 pod has a toleration that matches the taint.
Why it's wrong here
The error says 'didn't tolerate'.
The nodes do not have enough CPU or memory.
Why it's wrong here
Resource constraints show different messages.
Common exam traps
Cisco often tests the distinction between taint types — candidates confuse `unreachable` with resource-based taints like `disk-pressure` or `insufficient-memory`, or assume a toleration would solve the issue when the problem is that no toleration exists.
Trap categories for this question
Command / output trap
Resource constraints show different messages.
Detailed technical explanation
The `node.kubernetes.io/unreachable` taint is set by the node-lifecycle controller when the node has been unreachable for a period defined by `--node-monitor-grace-period` (default 40 seconds). This taint has a default `NoExecute` effect, which evicts existing pods without tolerations, and `NoSchedule` effect, preventing new pods. In a real-world scenario, a network partition or kubelet crash on all nodes would cause this exact error, and simply restarting the kubelet or fixing the network would remove the taint after the grace period.
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 KCNA 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
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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FAQ
Kubernetes Fundamentals — This question tests Kubernetes Fundamentals — Read the scenario before looking for a memorised answer..
The correct answer is: All nodes are unreachable or have been cordoned. — The taint `node.kubernetes.io/unreachable` is automatically added by the node controller when a node becomes unreachable (e.g., network failure, kubelet stops heartbeating). The error shows all 4 nodes have this taint and the pod has no matching toleration, meaning the scheduler cannot place the pod. This directly indicates all nodes are unreachable or have been cordoned (which also adds the `node.kubernetes.io/unschedulable` taint, but here the specific taint is `unreachable`).
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 11, 2026
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.
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