200-901 Application Deployment and Security Practice Question
This 200-901 practice question tests your understanding of application deployment and security. 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.
A Kubernetes cluster is configured with a NetworkPolicy that allows ingress traffic only from pods with label 'app: frontend'. A new backend service needs to communicate with the database pod. What must be done to allow this?
Deleting the policy would remove all restrictions, which is less secure and not best practice.
B
Add label 'app: backend' to the database pod
Why wrong: Adding label to database pod does not change the policy; the policy controls ingress sources.
C
Modify the NetworkPolicy to include an additional rule allowing from pods with label 'app: backend'
Why wrong: NetworkPolicies can include multiple ingress rules; adding one for 'app: backend' allows backend communication.
D
Create a new NetworkPolicy for the database
Why wrong: A new policy would need to be additive; but if the existing policy is default deny, a new policy with allow rule works, but modifying existing is simpler and avoids conflicts.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Delete the existing NetworkPolicy
Option A is correct because the existing NetworkPolicy explicitly restricts ingress traffic to only pods with the label 'app: frontend'. Since the new backend service does not have this label, its traffic will be blocked by the policy. Deleting the NetworkPolicy removes all ingress restrictions, allowing the backend service to communicate with the database pod. In Kubernetes, NetworkPolicies are additive and default-deny if any policy selects the pod, so removing the policy is the simplest way to permit all ingress traffic.
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.
✓
Delete the existing NetworkPolicy
Why this is correct
Deleting the policy would remove all restrictions, which is less secure and not best practice.
Related concept
Read the scenario before looking for a memorised answer.
✗
Add label 'app: backend' to the database pod
Why it's wrong here
Adding label to database pod does not change the policy; the policy controls ingress sources.
✗
Modify the NetworkPolicy to include an additional rule allowing from pods with label 'app: backend'
Why it's wrong here
NetworkPolicies can include multiple ingress rules; adding one for 'app: backend' allows backend communication.
✗
Create a new NetworkPolicy for the database
Why it's wrong here
A new policy would need to be additive; but if the existing policy is default deny, a new policy with allow rule works, but modifying existing is simpler and avoids conflicts.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates assume you must always modify or add policies to allow new traffic, but Cisco tests whether you understand that deleting a restrictive NetworkPolicy is a valid (though less secure) method to permit all traffic, especially when the question does not specify a security requirement.
Detailed technical explanation
How to think about this question
Kubernetes NetworkPolicies are implemented by the CNI plugin (e.g., Calico, Cilium) using iptables or eBPF rules. When a pod is selected by a NetworkPolicy, all traffic not explicitly allowed by any policy is dropped by default (default-deny behavior). If multiple policies select the same pod, the effective rule is the union of all allowed traffic; thus, deleting the existing policy removes the default-deny for that pod, allowing all ingress traffic. In a real-world scenario, a better practice would be to modify the policy to include the backend label, preserving security for other services, but the question's correct answer is deletion.
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 security administrator must allow nursing staff to reach a patient records server while blocking access from the guest Wi-Fi VLAN. After applying an extended ACL, traffic is still blocked from nursing workstations. The ACL was applied outbound instead of inbound on the wrong interface. Questions like this test ACL direction and placement rules.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Application Deployment and Security — This question tests Application Deployment and Security — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Delete the existing NetworkPolicy — Option A is correct because the existing NetworkPolicy explicitly restricts ingress traffic to only pods with the label 'app: frontend'. Since the new backend service does not have this label, its traffic will be blocked by the policy. Deleting the NetworkPolicy removes all ingress restrictions, allowing the backend service to communicate with the database pod. In Kubernetes, NetworkPolicies are additive and default-deny if any policy selects the pod, so removing the policy is the simplest way to permit all ingress traffic.
What should I do if I get this 200-901 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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