The correct answer is a NetworkPolicy in the 'db' namespace with `podSelector: {}` and an ingress rule from namespace 'app'. This works because an empty `podSelector: {}` selects all pods within the target namespace, while the ingress `from` clause specifying `namespaceSelector: matchLabels: kubernetes.io/metadata.name: app` combined with an empty `podSelector` allows traffic from any pod in the 'app' namespace, effectively creating a namespace-level isolation gate. On the CKA exam, this scenario tests your understanding that NetworkPolicies are namespace-scoped resources and must be deployed in the destination namespace—a common trap is placing the policy in the source namespace instead. Remember the rule of thumb: the policy lives where the traffic lands, not where it leaves. A helpful mnemonic is "Ingress In, Egress Out"—for allowing inbound traffic, always write the policy in the receiving namespace.
CKA Practice Question: Cluster Architecture, Installation and Configuration
This CKA practice question tests your understanding of cluster architecture, installation and configuration. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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 allow a specific pod running in namespace 'app' to communicate with a database pod in namespace 'db' only. Which NetworkPolicy configuration achieves this?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
NetworkPolicy in namespace 'db' with podSelector: {} and ingress from namespace 'app'
Option B is correct because a NetworkPolicy in the 'db' namespace with an empty podSelector: {} selects all pods in that namespace, and the ingress rule from namespace 'app' with an empty podSelector: {} allows traffic from any pod in the 'app' namespace. This configuration restricts inbound traffic to the database pods exclusively to pods from the 'app' namespace, meeting the requirement.
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.
✗
NetworkPolicy in namespace 'db' with podSelector: {} and ingress from namespace 'app' and podSelector: {}
Why it's wrong here
The podSelector in ingress is optional; this is similar but the correct answer is B.
✓
NetworkPolicy in namespace 'db' with podSelector: {} and ingress from namespace 'app'
Why this is correct
This policy allows ingress to all pods in 'db' from any pod in 'app'.
Related concept
Read the scenario before looking for a memorised answer.
✗
NetworkPolicy in namespace 'app' with egress to namespace 'db' and podSelector: {}
Why it's wrong here
Egress rules are more complex; the simplest is ingress on the target namespace.
✗
NetworkPolicy in namespace 'app' allowing ingress from namespace 'db'
Why it's wrong here
This would allow traffic from 'db' to 'app', not the reverse.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often think a NetworkPolicy must be placed in the source namespace (e.g., 'app') to control egress, but the correct approach is to place the policy in the destination namespace ('db') to restrict ingress, and they may also overlook that an empty podSelector: {} selects all pods, not a specific one.
Trap categories for this question
Similar concept trap
The podSelector in ingress is optional; this is similar but the correct answer is B.
Detailed technical explanation
How to think about this question
NetworkPolicies are namespace-scoped and apply to pods selected by the podSelector in the policy's spec. When using ingress rules, the from field can specify namespace selectors, pod selectors, or IP blocks; an empty podSelector: {} within a from block selects all pods in the specified namespace. The policy in Option B uses a namespace selector (namespace: app) without a pod selector, which means all pods in the 'app' namespace are allowed, but to restrict to a specific pod, you would need to add a podSelector with labels matching that specific pod. In a real-world scenario, you might use labels like 'role: frontend' to precisely target the allowed pod.
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: NetworkPolicy in namespace 'db' with podSelector: {} and ingress from namespace 'app' — Option B is correct because a NetworkPolicy in the 'db' namespace with an empty podSelector: {} selects all pods in that namespace, and the ingress rule from namespace 'app' with an empty podSelector: {} allows traffic from any pod in the 'app' namespace. This configuration restricts inbound traffic to the database pods exclusively to pods from the 'app' namespace, meeting the requirement.
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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