CKS NetworkPolicy Practice Question
In Kubernetes, you need to enforce a default deny-all network policy for pods in a specific namespace to ensure pods cannot communicate unless explicitly allowed by policy. Which resource should you create?
⚠ Common exam trap
Candidates often confuse namespace-scoped controls: ResourceQuota and LimitRange limit resource consumption, while NetworkPolicy is the only one of these that enforces pod-to-pod network segmentation.
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
✓
NetworkPolicy
A NetworkPolicy is the Kubernetes resource that controls network traffic to and from pods. A default deny-all policy can be created by selecting all pods (e.g., using an empty podSelector) and omitting ingress/egress rules. ResourceQuota and LimitRange manage compute/resource usage, not network traffic, and RuntimeClass selects a container runtime configuration rather than enforcing network policy.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
NetworkPolicy
Why this is correct
A NetworkPolicy with an empty pod selector and both Ingress and Egress policyTypes set to deny enforces default deny-all for every pod in the namespace, satisfying the requirement that communication is blocked unless explicitly permitted. Kubernetes' native policy object operates at layer 3/4, matching the namespace-scoped constraint in the stem.
- ✗
ResourceQuota
Why it's wrong here
ResourceQuota caps aggregate namespace consumption of CPU, memory, object counts and storage; it never evaluates pod selectors or traffic direction. It is tempting because it is a namespace-scoped admission control, and would be correct when you must limit total resource usage across a namespace.
- ✗
LimitRange
Why it's wrong here
LimitRange sets per-pod or per-container CPU, memory and storage defaults and limits within a namespace; it does not select pods or define ingress/egress rules. It is tempting because it also governs namespace-level pod behaviour, and would be correct when you need to constrain resource requests.
- ✗
RuntimeClass
Why it's wrong here
RuntimeClass selects which container runtime configuration (for example gVisor or Kata) a pod uses; it has no network policy semantics. It is tempting as another pod-level isolation mechanism, and would be correct when you need stronger workload sandboxing rather than traffic denial.
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Senior Network & Security Engineer · founder of Courseiva
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