This CKS practice question tests your understanding of supply chain security. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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 cluster has the ImagePolicyWebhook admission controller enabled. A pod creation is denied with the message 'image policy check failed'. The webhook server returns an error. Which of the following could be a valid reason?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The image is not signed by a trusted authority
The ImagePolicyWebhook can reject images based on external policy. If the image is not signed or the signature cannot be verified, the webhook may deny the request.
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
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 image is not signed by a trusted authority
Why this is correct
The webhook can be configured to require signatures, and if missing, the pod is denied.
Related concept
Static NAT maps one inside address to one outside address.
✗
The container runtime is out of date
Why it's wrong here
Container runtime version is not checked by ImagePolicyWebhook.
✗
The image tag does not exist in the registry
Why it's wrong here
ImagePolicyWebhook does not check tag existence; it checks policy.
✗
The pod specification has a hostNetwork: true
Why it's wrong here
HostNetwork is not related to image policy.
Common exam traps
Common exam trap: NAT rules depend on direction and matching traffic
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Detailed technical explanation
How to think about this question
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
KKey Concepts to Remember
Static NAT maps one inside address to one outside address.
PAT allows many inside hosts to share one public address using ports.
Inside local and inside global describe the private and translated addresses.
NAT ACLs identify traffic for translation, not always security filtering.
TExam Day Tips
→Identify inside and outside interfaces first.
→Check whether the scenario needs static NAT, dynamic NAT or PAT.
→Do not confuse NAT matching ACLs with normal packet-filtering intent.
Key takeaway
NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Real-world example
How this comes up in practice
A small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this CKS question in full detail.
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related CKS NAT questions on configuration and troubleshooting.
Supply Chain Security — This question tests Supply Chain Security — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: The image is not signed by a trusted authority — The ImagePolicyWebhook can reject images based on external policy. If the image is not signed or the signature cannot be verified, the webhook may deny the request.
What should I do if I get this CKS question wrong?
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related CKS NAT questions on configuration and troubleshooting.
What is the key concept behind this question?
Static NAT maps one inside address to one outside address.
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Question Discussion
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