This 200-901 practice question tests your understanding of network fundamentals. 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 DevOps team is automating network configuration using Ansible. They want to push a new VLAN configuration to a switch but ensure that only one switch is updated at a time to avoid network disruption. Which Ansible strategy or feature should they use?
Why wrong: Ansible has 'linear' (default) and 'free' strategies, but 'free' does not limit batch size; it allows hosts to finish independently.
B
Set 'forks: 1' in the playbook.
Why wrong: 'forks' controls how many hosts are processed simultaneously per task, not per play, but it might still update multiple switches in parallel across tasks.
C
Use 'throttle: 1' on each task.
Why wrong: 'throttle' limits concurrent task execution but still allows multiple hosts to proceed in parallel across different tasks.
D
Set 'serial: 1' in the playbook.
'serial: 1' ensures only one host is updated at a time, preventing disruption.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Set 'serial: 1' in the playbook.
Option D is correct because setting `serial: 1` in an Ansible playbook forces the play to execute against only one host at a time, even if the play targets multiple switches. This ensures that VLAN configuration is pushed to exactly one switch before moving to the next, preventing network disruption from simultaneous changes.
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.
✗
Use 'strategy: free' to manage execution order.
Why it's wrong here
Ansible has 'linear' (default) and 'free' strategies, but 'free' does not limit batch size; it allows hosts to finish independently.
✗
Set 'forks: 1' in the playbook.
Why it's wrong here
'forks' controls how many hosts are processed simultaneously per task, not per play, but it might still update multiple switches in parallel across tasks.
✗
Use 'throttle: 1' on each task.
Why it's wrong here
'throttle' limits concurrent task execution but still allows multiple hosts to proceed in parallel across different tasks.
✓
Set 'serial: 1' in the playbook.
Why this is correct
'serial: 1' ensures only one host is updated at a time, preventing disruption.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates confuse `forks` (which controls task-level parallelism) with `serial` (which controls host-level batching), or mistakenly think `throttle` or `strategy: free` can achieve the same serialization effect.
Detailed technical explanation
How to think about this question
The `serial` keyword in Ansible controls the batch size of hosts that are processed together in a play. When set to `1`, Ansible runs the entire play (all tasks) on one host, then moves to the next, effectively serializing the deployment. This is critical for network automation where configuration changes (e.g., VLAN creation, STP topology adjustments) must be applied one device at a time to avoid loops or outages. Under the hood, Ansible uses an internal host queue and processes batches sequentially, waiting for all tasks in the current batch to complete before starting the next.
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 help-desk technician troubleshoots why a newly connected PC cannot reach shared printers on the same floor. The cable is good, the switch port is active, but the PC is in VLAN 20 and the printers are in VLAN 10. The uplink trunk only allows VLAN 10. A trunk being up does not mean every VLAN crosses it.
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.
Network Fundamentals — This question tests Network Fundamentals — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Set 'serial: 1' in the playbook. — Option D is correct because setting `serial: 1` in an Ansible playbook forces the play to execute against only one host at a time, even if the play targets multiple switches. This ensures that VLAN configuration is pushed to exactly one switch before moving to the next, preventing network disruption from simultaneous changes.
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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