- A
Ensure Service A's pod has the label 'app: frontend' on its pod spec
Why wrong: Incorrect. A podSelector alone matches pods in the same namespace only, so adding the label to Service A's pod in the 'default' namespace will not allow ingress from the 'backend' namespace's NetworkPolicy.
- B
Add a similar NetworkPolicy in the 'default' namespace allowing egress to the 'backend' namespace
Why wrong: Incorrect. Egress policies control outbound traffic from pods in the 'default' namespace, but the traffic direction is from Service A (default) to Service B (backend), so an ingress policy on the backend namespace controls access. Adding an egress policy is not necessary and does not allow the traffic.
- C
Change the NetworkPolicy to allow all ingress traffic from any source
Why wrong: Incorrect. Changing the policy to allow all ingress is too permissive and violates security best practices. The proper approach is to use a namespaceSelector to restrict cross-namespace traffic.
- D
Add a label to the 'default' namespace matching the NetworkPolicy's namespaceSelector
Correct. By adding a label to the 'default' namespace and including a namespaceSelector matching that label in the NetworkPolicy, you allow ingress from pods in the 'default' namespace. Combined with the podSelector for 'app: frontend', this enables Service A to reach Service B.
Kubernetes NetworkPolicy: Allow Cross-Namespace Ingress
This KCNA practice question tests your understanding of container orchestration. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. A key principle to apply: networkPolicy podSelector. 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 have a microservices application where Service A needs to communicate with Service B running in a different namespace ('backend'). Both namespaces have a NetworkPolicy that denies all ingress by default. You create a NetworkPolicy in the 'backend' namespace allowing ingress from pods with label 'app: frontend'. What else is needed for Service A to reach Service B?
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
Add a label to the 'default' namespace matching the NetworkPolicy's namespaceSelector
Option D is correct. A NetworkPolicy with only a podSelector in an ingress rule matches pods in the same namespace only. To allow cross-namespace traffic, you must include a namespaceSelector that selects the namespace of the source pods. By adding a label to the 'default' namespace and including a namespaceSelector matching that label in the NetworkPolicy, you enable Service A's pods to be allowed. Ensure Service A's pod also has the required label 'app: frontend'. Option A is wrong: a podSelector alone only matches pods in the same namespace. Option B is wrong: egress policies are not needed for inbound traffic. Option C is too permissive and unnecessary.
Key principle: NetworkPolicy podSelector
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Ensure Service A's pod has the label 'app: frontend' on its pod spec
Why it's wrong here
Incorrect. A podSelector alone matches pods in the same namespace only, so adding the label to Service A's pod in the 'default' namespace will not allow ingress from the 'backend' namespace's NetworkPolicy.
- ✗
Add a similar NetworkPolicy in the 'default' namespace allowing egress to the 'backend' namespace
Why it's wrong here
Incorrect. Egress policies control outbound traffic from pods in the 'default' namespace, but the traffic direction is from Service A (default) to Service B (backend), so an ingress policy on the backend namespace controls access. Adding an egress policy is not necessary and does not allow the traffic.
- ✗
Change the NetworkPolicy to allow all ingress traffic from any source
Why it's wrong here
Incorrect. Changing the policy to allow all ingress is too permissive and violates security best practices. The proper approach is to use a namespaceSelector to restrict cross-namespace traffic.
- ✓
Add a label to the 'default' namespace matching the NetworkPolicy's namespaceSelector
Why this is correct
Correct. By adding a label to the 'default' namespace and including a namespaceSelector matching that label in the NetworkPolicy, you allow ingress from pods in the 'default' namespace. Combined with the podSelector for 'app: frontend', this enables Service A to reach Service B.
Related concept
NetworkPolicy podSelector
Common exam traps
Common exam trap: answer the scenario, not the keyword
A common pitfall is to assume that a podSelector in an ingress rule can match pods across namespaces without a namespaceSelector. In reality, a podSelector only matches pods in the same namespace unless combined with a namespaceSelector.
Detailed technical explanation
How to think about this question
Under the hood, Kubernetes NetworkPolicy rules are enforced by the CNI plugin (e.g., Calico, Cilium) using iptables or eBPF. The podSelector in a NetworkPolicy is scoped to the namespace where the policy is defined; to allow cross-namespace traffic, you must either use a namespaceSelector in combination with a podSelector or ensure the source pod's label matches the podSelector. A common real-world scenario is when a frontend service in a 'frontend' namespace needs to reach a backend service in a 'backend' namespace; the backend's NetworkPolicy must explicitly allow ingress from pods with the correct label, and the frontend pods must carry that label.
KKey Concepts to Remember
- NetworkPolicy podSelector
- namespaceSelector
- Combined podSelector and namespaceSelector
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
NetworkPolicy podSelector
Real-world example
How this comes up in practice
A practitioner preparing for the KCNA 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. NetworkPolicy podSelector Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
What to study next
Got this wrong? Here's your next step.
Review networkPolicy podSelector, then practise related KCNA questions on the same topic to reinforce the concept.
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FAQ
Questions learners often ask
What does this KCNA question test?
Container Orchestration — This question tests Container Orchestration — NetworkPolicy podSelector.
What is the correct answer to this question?
The correct answer is: Add a label to the 'default' namespace matching the NetworkPolicy's namespaceSelector — Option D is correct. A NetworkPolicy with only a podSelector in an ingress rule matches pods in the same namespace only. To allow cross-namespace traffic, you must include a namespaceSelector that selects the namespace of the source pods. By adding a label to the 'default' namespace and including a namespaceSelector matching that label in the NetworkPolicy, you enable Service A's pods to be allowed. Ensure Service A's pod also has the required label 'app: frontend'. Option A is wrong: a podSelector alone only matches pods in the same namespace. Option B is wrong: egress policies are not needed for inbound traffic. Option C is too permissive and unnecessary.
What should I do if I get this KCNA question wrong?
Review networkPolicy podSelector, then practise related KCNA questions on the same topic to reinforce the concept.
What is the key concept behind this question?
NetworkPolicy podSelector
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Last reviewed: Jun 30, 2026
This KCNA 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 KCNA exam.
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