This CKS practice question tests your understanding of cluster 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.
Which TWO of the following are valid ways to restrict access to the Kubernetes API server?
Use static token file
Why wrong: Insecure and deprecated.
Use webhook token authentication
Valid authentication method.
Enable NodeRestriction admission plugin
Why wrong: Limits kubelet, not API server clients.
Configure RBAC authorization
RBAC is the standard authorization mode.
Enable anonymous access
Why wrong: Allows unauthenticated access.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Use webhook token authentication
Webhook token authentication (Option B) is a valid method to restrict API server access because it delegates token validation to an external service via a webhook, allowing custom authentication logic. This is a supported authentication strategy in Kubernetes, enabling fine-grained control over who can access the API server.
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.
Use static token file
Why it's wrong here
Insecure and deprecated.
Use webhook token authentication
Why this is correct
Valid authentication method.
Related concept
Read the scenario before looking for a memorised answer.
Enable NodeRestriction admission plugin
Why it's wrong here
Limits kubelet, not API server clients.
Configure RBAC authorization
Why this is correct
RBAC is the standard authorization mode.
Related concept
Read the scenario before looking for a memorised answer.
Enable anonymous access
Why it's wrong here
Allows unauthenticated access.
Common exam traps
CNCF often tests the distinction between authentication (who you are) and authorization (what you can do), so candidates may confuse RBAC (authorization) with authentication mechanisms like webhook tokens, but the question asks for ways to 'restrict access,' which includes both authentication and authorization controls.
Detailed technical explanation
Webhook token authentication works by configuring the API server with the `--authentication-token-webhook-config-file` flag, which points to a kubeconfig file for an external service that validates bearer tokens. This external service can integrate with OIDC providers, LDAP, or custom identity systems, and the API server caches token reviews for a configurable duration (default 2 minutes) to reduce load. In real-world scenarios, this is often used with enterprise SSO solutions like Azure AD or Okta to enforce centralized access policies.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A junior network technician can log in to a core router but cannot reach the enable prompt or configuration mode. The AAA server is authenticating the login — but the authorisation policy only grants privilege level 1, not 15. Authentication (who you are) is working; authorisation (what you can do) is not.
What to study next
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FAQ
Cluster Hardening — This question tests Cluster Hardening — Read the scenario before looking for a memorised answer..
The correct answer is: Use webhook token authentication — Webhook token authentication (Option B) is a valid method to restrict API server access because it delegates token validation to an external service via a webhook, allowing custom authentication logic. This is a supported authentication strategy in Kubernetes, enabling fine-grained control over who can access the API server.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 30, 2026
This CKS 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 CKS exam.
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