CKA Practice Question: Cluster Architecture, Installation & Configuration
This CKA practice question tests your understanding of cluster architecture, installation & 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 Kubernetes cluster has three control plane nodes and five worker nodes. The kube-apiserver is failing to start on one control plane node with the error 'etcdserver: request timed out'. The etcd cluster is healthy with three members. Which of the following 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.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
A firewall is blocking traffic on port 2379 between the control plane and etcd
The error 'etcdserver: request timed out' indicates that the kube-apiserver cannot establish a TCP connection to the etcd cluster within the timeout period. Since the etcd cluster is healthy with three members and leader election is functioning, the most likely cause is a firewall blocking port 2379 (the etcd client port) between the control plane node and the etcd members. This prevents the kube-apiserver from communicating with etcd, even though the etcd cluster itself is operational.
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.
✓
A firewall is blocking traffic on port 2379 between the control plane and etcd
Why this is correct
Port 2379 is used for etcd client requests; blocking it would cause timeouts.
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 etcd cluster has a leader election issue
Why it's wrong here
The etcd cluster is reported as healthy, so leader election is not the issue.
✗
The kube-apiserver is using the wrong etcd client port (2380 instead of 2379)
Why it's wrong here
Port 2380 is for etcd peer communication, not client requests.
✗
The etcd client certificate is expired
Why it's wrong here
An expired certificate would cause a TLS error, not a generic timeout.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often assume a timeout error implies an etcd cluster problem (like leader election or node failure), but the question explicitly states the etcd cluster is healthy, shifting the focus to network connectivity between the apiserver and etcd.
Detailed technical explanation
How to think about this question
The kube-apiserver connects to etcd via the client port 2379 using gRPC, and the default timeout for etcd requests is typically 1-2 seconds. A firewall rule blocking TCP/2379 would cause the connection to hang until the timeout expires, producing the exact error seen. In a multi-control-plane setup, each apiserver must reach all etcd members; a network policy or security group misconfiguration on a single node is a common real-world issue.
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 & Configuration — This question tests Cluster Architecture, Installation & Configuration — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: A firewall is blocking traffic on port 2379 between the control plane and etcd — The error 'etcdserver: request timed out' indicates that the kube-apiserver cannot establish a TCP connection to the etcd cluster within the timeout period. Since the etcd cluster is healthy with three members and leader election is functioning, the most likely cause is a firewall blocking port 2379 (the etcd client port) between the control plane node and the etcd members. This prevents the kube-apiserver from communicating with etcd, even though the etcd cluster itself is operational.
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.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
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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