KCNA Kubernetes Fundamentals Practice Question
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?
⚠ Common exam trap
The KCNA exam 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.
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
✓
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`).
Answer analysis
Option-by-option breakdown
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.
- ✗
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.
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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.