This KCNA practice question tests your understanding of kubernetes fundamentals. 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 team uses a Deployment with 3 replicas and a RollingUpdate strategy. They update the container image. During the update, one of the new pods fails to start. What will happen by default?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The update pauses, keeping the remaining old replicas running
By default, a Deployment with a RollingUpdate strategy uses a `maxUnavailable` of 25% and a `maxSurge` of 25%. When a new pod fails to start (e.g., CrashLoopBackOff or ImagePullBackOff), the ReplicaSet controller will not create additional new pods beyond the surge limit, and the update will effectively pause because the new ReplicaSet cannot reach its desired replica count. The old ReplicaSet remains running with its existing pods, ensuring availability is maintained.
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.
✓
The update pauses, keeping the remaining old replicas running
Why this is correct
The rolling update stops when a new pod fails, ensuring availability of old pods.
Related concept
Read the scenario before looking for a memorised answer.
✗
The entire update is rolled back and all old pods are deleted
Why it's wrong here
This would cause disruption, which the controller avoids.
✗
The Deployment automatically rolls back to the previous image
Why it's wrong here
Automatic rollback is not default; manual intervention or a rollout undo command is needed.
✗
The failed pod is terminated and not retried
Why it's wrong here
The controller retries the pod creation until it succeeds or the update is paused.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misconception that a failed pod in a rolling update triggers an automatic rollback or deletion, when in fact the default behavior is to pause the update and keep old replicas running until the issue is resolved manually.
Trap categories for this question
Command / output trap
Automatic rollback is not default; manual intervention or a rollout undo command is needed.
Detailed technical explanation
How to think about this question
Under the hood, the Deployment controller manages two ReplicaSets during a rolling update: the old one (with the previous image) and the new one (with the updated image). The `maxSurge` and `maxUnavailable` parameters control the pace. When a new pod fails, the new ReplicaSet's status shows a `ReplicaFailure` condition, and the controller stops scaling up further, effectively pausing the update. In real-world scenarios, this prevents cascading failures and allows operators to diagnose issues (e.g., using `kubectl describe deployment` or checking pod logs) without losing service capacity.
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 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 KCNA question in full detail.
Kubernetes Fundamentals — This question tests Kubernetes Fundamentals — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The update pauses, keeping the remaining old replicas running — By default, a Deployment with a RollingUpdate strategy uses a `maxUnavailable` of 25% and a `maxSurge` of 25%. When a new pod fails to start (e.g., CrashLoopBackOff or ImagePullBackOff), the ReplicaSet controller will not create additional new pods beyond the surge limit, and the update will effectively pause because the new ReplicaSet cannot reach its desired replica count. The old ReplicaSet remains running with its existing pods, ensuring availability is maintained.
What should I do if I get this KCNA 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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Question Discussion
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