This CKA practice question tests your understanding of services and networking. 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. 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.
After creating a NetworkPolicy that selects pods with label 'role: db' and allows ingress on TCP port 3306 from pods with label 'role: api', you notice that pods with label 'role: db' are still reachable on port 3306 from pods without 'role: api' label. What is the most likely cause?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The NetworkPolicy is not in the same namespace as the pods.
NetworkPolicy is only effective if there is at least one policy selecting the pod; however, if no policy exists that matches, it defaults to allow. But here a policy exists, so it should restrict. The most likely cause is that the policy is missing a rule to explicitly deny other sources, but NetworkPolicy works by whitelisting: if a pod is selected by any policy, only traffic that matches an ingress rule is allowed. So if the policy allows from 'role: api', then only those pods should be allowed. If other pods can still reach, the policy might not be applied correctly, e.g., wrong namespace. But the most common mistake is that the policy's podSelector does not match the pod's label.
Key principle: ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
The NetworkPolicy is not in the same namespace as the pods.
Why this is correct
NetworkPolicy only applies within its namespace. If the policy is in a different namespace, it won't affect the pods.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Standard ACLs match source addresses.
✗
The NetworkPolicy uses the wrong protocol.
Why it's wrong here
The protocol is likely TCP, which is correct for MySQL.
✗
The NetworkPolicy has an egress rule that overrides ingress.
Why it's wrong here
Egress rules do not affect ingress.
✗
The NetworkPolicy requires an explicit 'deny all' rule.
Why it's wrong here
NetworkPolicy does not require a deny all; it implicitly denies if no rule matches.
Common exam traps
Common exam trap: ACLs stop at the first match
ACLs are processed top to bottom. The first matching entry wins, and an implicit deny usually exists at the end.
Detailed technical explanation
How to think about this question
ACL questions test precision: source, destination, protocol, port and direction. A generally correct ACL can still fail if it is applied on the wrong interface or in the wrong direction.
KKey Concepts to Remember
Standard ACLs match source addresses.
Extended ACLs can match source, destination, protocol and ports.
The first matching ACL entry is used.
There is usually an implicit deny at the end.
TExam Day Tips
→Check inbound versus outbound direction.
→Read the ACL from top to bottom.
→Look for a broader permit or deny above the intended line.
Key takeaway
ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.
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.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this CKA question in full detail.
Review ACL processing order, placement rules (standard near destination, extended near source), and inbound vs outbound direction. Study wildcard masks and implicit deny. Then practise related CKA ACL questions on filtering logic and placement.
Services and Networking — This question tests Services and Networking — Standard ACLs match source addresses..
What is the correct answer to this question?
The correct answer is: The NetworkPolicy is not in the same namespace as the pods. — NetworkPolicy is only effective if there is at least one policy selecting the pod; however, if no policy exists that matches, it defaults to allow. But here a policy exists, so it should restrict. The most likely cause is that the policy is missing a rule to explicitly deny other sources, but NetworkPolicy works by whitelisting: if a pod is selected by any policy, only traffic that matches an ingress rule is allowed. So if the policy allows from 'role: api', then only those pods should be allowed. If other pods can still reach, the policy might not be applied correctly, e.g., wrong namespace. But the most common mistake is that the policy's podSelector does not match the pod's label.
What should I do if I get this CKA question wrong?
Review ACL processing order, placement rules (standard near destination, extended near source), and inbound vs outbound direction. Study wildcard masks and implicit deny. Then practise related CKA ACL questions on filtering logic and placement.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Standard ACLs match source addresses.
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