This CKA practice question tests your understanding of troubleshooting. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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 have a Deployment with one replica. The Pod enters CrashLoopBackOff. 'kubectl describe pod' shows the container exits with code 137. 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 container is exceeding its memory limit and is OOMKilled
Exit code 137 (SIGKILL) typically indicates the container was killed by the OOM killer due to exceeding memory limits. Option B is correct. Option A (liveness probe) would exit with code other than 137. Option C (invalid command) would exit with non-zero code but not specifically 137. Option D (node restart) would result in pod being rescheduled rather than crash loop.
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 node is being drained and the pod is being terminated
Why it's wrong here
Draining would result in pod being rescheduled, not crash loop.
✗
The container's startup command is invalid
Why it's wrong here
Invalid command would exit with code 2 or similar, not 137.
✓
The container is exceeding its memory limit and is OOMKilled
Why this is correct
Exit code 137 is SIGKILL, often due to OOM.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Static NAT maps one inside address to one outside address.
✗
The liveness probe is failing and Kubernetes is restarting the container
Why it's wrong here
Liveness probe failures exit with code different from 137.
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.
Trap categories for this question
Similar concept trap
Invalid command would exit with code 2 or similar, not 137.
Command / output trap
Invalid command would exit with code 2 or similar, not 137.
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 CKA 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 CKA NAT questions on configuration and troubleshooting.
Troubleshooting — This question tests Troubleshooting — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: The container is exceeding its memory limit and is OOMKilled — Exit code 137 (SIGKILL) typically indicates the container was killed by the OOM killer due to exceeding memory limits. Option B is correct. Option A (liveness probe) would exit with code other than 137. Option C (invalid command) would exit with non-zero code but not specifically 137. Option D (node restart) would result in pod being rescheduled rather than crash loop.
What should I do if I get this CKA 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 CKA NAT questions on configuration and troubleshooting.
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?
Static NAT maps one inside address to one outside address.
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