The correct next step is to upgrade the control plane nodes to v1.29. This is because Kubernetes enforces a strict version skew policy: the kube-apiserver must never be older than the kubelet on any node, and worker nodes can only be one minor version ahead of the control plane. Since you have already upgraded and drained all worker nodes to v1.29, the control plane nodes running v1.28 would violate this policy, risking API compatibility issues and cluster instability. On the CKA exam, this scenario tests your understanding of the upgrade order and version skew constraints—a common trap is thinking you must upgrade the control plane first, but the real requirement is that the control plane must be at the target version before or after the workers, as long as the skew rule is respected. Remember the memory tip: "Control plane sets the floor, workers can go one step ahead, but never leave the API behind."
CKA Practice Question: Cluster Architecture, Installation and Configuration
This CKA practice question tests your understanding of cluster architecture, installation and configuration. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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.
You are upgrading a cluster from v1.28 to v1.29. You have already drained and upgraded all worker nodes. The control plane nodes have not been upgraded yet. 'kubectl get nodes' shows the control plane nodes are still v1.28. What is the correct next step?
Drain the worker nodes and downgrade them to v1.28
Why wrong: Downgrading is not recommended and may cause issues; the correct order is to upgrade control plane first.
B
Uncordon the worker nodes
Why wrong: Uncordoning would allow scheduling onto worker nodes that may have a higher version than the API server, which could cause compatibility issues.
C
Upgrade the control plane nodes to v1.29
Control plane must be upgraded before or in coordination with worker nodes. Since workers are already upgraded, upgrade the control plane now.
D
Restart the kubelet on all nodes
Why wrong: Restarting kubelet will not upgrade the control plane components.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Upgrade the control plane nodes to v1.29
The correct next step is to upgrade the control plane nodes to v1.29. In a Kubernetes cluster upgrade, the control plane must be upgraded before or in conjunction with the worker nodes, but since the worker nodes have already been upgraded and drained, the control plane nodes are still running v1.28. Upgrading the control plane nodes ensures that the API server, scheduler, and controller manager are at the target version, which is required for cluster stability and to support the upgraded kubelets on the worker nodes.
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.
✗
Drain the worker nodes and downgrade them to v1.28
Why it's wrong here
Downgrading is not recommended and may cause issues; the correct order is to upgrade control plane first.
✗
Uncordon the worker nodes
Why it's wrong here
Uncordoning would allow scheduling onto worker nodes that may have a higher version than the API server, which could cause compatibility issues.
✓
Upgrade the control plane nodes to v1.29
Why this is correct
Control plane must be upgraded before or in coordination with worker nodes. Since workers are already upgraded, upgrade the control plane now.
Related concept
Read the scenario before looking for a memorised answer.
✗
Restart the kubelet on all nodes
Why it's wrong here
Restarting kubelet will not upgrade the control plane components.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates may think uncordoning worker nodes is safe after draining, but the CKA exam tests the understanding that the control plane must be upgraded before worker nodes are made schedulable again to avoid version skew issues.
Detailed technical explanation
How to think about this question
Kubernetes follows a strict version skew policy: the kubelet must not be newer than the kube-apiserver, and the kube-apiserver can be at most one minor version ahead of the kubelet. Upgrading the control plane first ensures the API server is at v1.29, which can then safely manage the v1.29 kubelets on worker nodes. The upgrade typically involves updating the kubeadm binary, running 'kubeadm upgrade plan' and 'kubeadm upgrade apply v1.29.0' on each control plane node, and then upgrading the kubelet and kubectl.
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: Upgrade the control plane nodes to v1.29 — The correct next step is to upgrade the control plane nodes to v1.29. In a Kubernetes cluster upgrade, the control plane must be upgraded before or in conjunction with the worker nodes, but since the worker nodes have already been upgraded and drained, the control plane nodes are still running v1.28. Upgrading the control plane nodes ensures that the API server, scheduler, and controller manager are at the target version, which is required for cluster stability and to support the upgraded kubelets on the worker nodes.
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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