This CKS practice question tests your understanding of cluster setup and hardening. 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 need to restrict access to etcd so that only the API server can communicate with it. Which method should you use?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Configure etcd with TLS client certificates and require authentication
Option A is correct because etcd supports mutual TLS (mTLS) authentication, which requires clients to present a valid TLS certificate signed by a trusted CA. By configuring etcd with `--client-cert-auth=true` and providing the API server's client certificate, you ensure that only the API server (or any client with a valid certificate) can communicate with etcd. This is the recommended Kubernetes approach to restrict access to etcd, as it cryptographically verifies the identity of the client.
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.
✓
Configure etcd with TLS client certificates and require authentication
Why this is correct
TLS client authentication ensures only authorized clients can connect.
Related concept
Read the scenario before looking for a memorised answer.
✗
Set the etcd flag --peer-auto-tls=true
Why it's wrong here
This is for peer communication, not client authentication.
✗
Configure etcd to use RBAC with a role that allows only the API server
Why it's wrong here
etcd RBAC is not typically used for this purpose; TLS client certificates are the standard.
✗
Use a firewall rule to restrict access to etcd's port from the API server's IP
Why it's wrong here
This is a network-level control, but TLS provides stronger authentication and encryption.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse network-level restrictions (firewall rules) with identity-based authentication (mTLS), or mistakenly think etcd supports RBAC like Kubernetes, leading them to choose options D or C.
Detailed technical explanation
How to think about this question
etcd's client authentication is controlled by the `--client-cert-auth` flag, which, when set to `true`, requires all clients to present a certificate signed by the CA specified in `--trusted-ca-file`. The API server is configured with `--etcd-certfile` and `--etcd-keyfile` to present its client certificate, and `--etcd-cafile` to verify the etcd server's certificate. In a real-world scenario, if an attacker gains access to the Kubernetes node but not the API server's client certificate, they cannot query etcd directly, preventing data exfiltration or cluster corruption.
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 CKS 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 CKS question in full detail.
Cluster Setup and Hardening — This question tests Cluster Setup and Hardening — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Configure etcd with TLS client certificates and require authentication — Option A is correct because etcd supports mutual TLS (mTLS) authentication, which requires clients to present a valid TLS certificate signed by a trusted CA. By configuring etcd with `--client-cert-auth=true` and providing the API server's client certificate, you ensure that only the API server (or any client with a valid certificate) can communicate with etcd. This is the recommended Kubernetes approach to restrict access to etcd, as it cryptographically verifies the identity of the client.
What should I do if I get this CKS 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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