- A
The Ansible control node is using an outdated version of the nxos_ospf module that does not support idempotency.
Why wrong: While module versions matter, the nxos_ospf module has supported idempotency for many releases; this is less likely than a configuration mismatch.
- B
The playbook does not specify all OSPF parameters, such as 'router-id', causing the module to detect a difference with the running configuration.
If the playbook omits parameters that the module manages (e.g., router-id defaults to a loopback IP), the module sees a change and marks it as 'changed'.
- C
The switches have different NX-OS versions, causing the module to behave inconsistently.
Why wrong: Version differences could cause issues, but the scenario states all switches report 'changed', suggesting a consistent cause, not version variability.
- D
The engineer forgot to use the '--check' flag to verify idempotency.
Why wrong: The --check flag only simulates changes; it does not affect whether the module is idempotent.
350-401 Ansible Automation Practice Question
This 350-401 practice question tests your understanding of ansible automation. 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.
An engineer is writing an Ansible playbook to configure OSPF on a fleet of Cisco Nexus 9000 switches. The playbook uses the nxos_ospf module. When executed, the playbook reports 'changed' for every switch, even on subsequent runs when no configuration changes are made. The engineer wants to achieve idempotent behavior. What is the most likely cause of the non-idempotent results?
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 choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
The playbook does not specify all OSPF parameters, such as 'router-id', causing the module to detect a difference with the running configuration.
The nxos_ospf module may report changes if the OSPF process configuration includes parameters that are not fully idempotent, such as the 'router-id' being set dynamically. However, a common cause is that the module compares the current state with the desired state, and if the switch returns extra default parameters (like 'log-adjacency-changes' or 'auto-cost') that are not specified in the playbook, the module may see a difference and report 'changed'. The most direct cause here is that the playbook does not specify all parameters that the module manages, leading to a mismatch.
Key principle: OSPF neighbour adjacency depends on matching area, hello/dead timers, network type, and authentication — IP reachability alone is not enough.
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 Ansible control node is using an outdated version of the nxos_ospf module that does not support idempotency.
Why it's wrong here
While module versions matter, the nxos_ospf module has supported idempotency for many releases; this is less likely than a configuration mismatch.
- ✓
The playbook does not specify all OSPF parameters, such as 'router-id', causing the module to detect a difference with the running configuration.
Why this is correct
If the playbook omits parameters that the module manages (e.g., router-id defaults to a loopback IP), the module sees a change and marks it as 'changed'.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
OSPF neighbours must agree on key parameters.
- ✗
The switches have different NX-OS versions, causing the module to behave inconsistently.
Why it's wrong here
Version differences could cause issues, but the scenario states all switches report 'changed', suggesting a consistent cause, not version variability.
- ✗
The engineer forgot to use the '--check' flag to verify idempotency.
Why it's wrong here
The --check flag only simulates changes; it does not affect whether the module is idempotent.
Common exam traps
Common exam trap: OSPF can fail even when IP connectivity looks correct
OSPF neighbour formation depends on matching areas, timers, network type, authentication and passive-interface behaviour. Do not choose an answer only because the devices can ping.
Trap categories for this question
Scenario analysis trap
Version differences could cause issues, but the scenario states all switches report 'changed', suggesting a consistent cause, not version variability.
Detailed technical explanation
How to think about this question
OSPF questions usually test the details that control adjacency and route selection. Read the neighbour state, area, router ID and interface configuration before deciding what is wrong.
KKey Concepts to Remember
- OSPF neighbours must agree on key parameters.
- Router ID selection can affect neighbour relationships and LSDB output.
- OSPF cost influences the preferred path.
- A route can appear in OSPF information but not become the installed route.
TExam Day Tips
- Check area mismatch first when OSPF adjacency fails.
- Review passive interfaces when a network is advertised but no neighbour forms.
- Use show ip ospf neighbor and show ip route clues carefully.
Key takeaway
OSPF neighbour adjacency depends on matching area, hello/dead timers, network type, and authentication — IP reachability alone is not enough.
Real-world example
How this comes up in practice
A network engineer at a university connects two campus buildings via a fibre link. Both routers run OSPF, but no adjacency forms — even though both routers can ping each other. The engineer finds one router is in area 0 and the other in area 1. OSPF adjacency requires matching area numbers, hello/dead timers, and network type. IP reachability alone is not enough.
What to study next
Got this wrong? Here's your next step.
Review OSPF neighbour requirements — matching area type, hello and dead timers, network type, stub flags, and authentication. Study show ip ospf neighbor states (INIT, 2-WAY, FULL). Then practise related 350-401 OSPF questions on adjacency and route selection.
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FAQ
Questions learners often ask
What does this 350-401 question test?
Ansible Automation — This question tests Ansible Automation — OSPF neighbours must agree on key parameters..
What is the correct answer to this question?
The correct answer is: The playbook does not specify all OSPF parameters, such as 'router-id', causing the module to detect a difference with the running configuration. — The nxos_ospf module may report changes if the OSPF process configuration includes parameters that are not fully idempotent, such as the 'router-id' being set dynamically. However, a common cause is that the module compares the current state with the desired state, and if the switch returns extra default parameters (like 'log-adjacency-changes' or 'auto-cost') that are not specified in the playbook, the module may see a difference and report 'changed'. The most direct cause here is that the playbook does not specify all parameters that the module manages, leading to a mismatch.
What should I do if I get this 350-401 question wrong?
Review OSPF neighbour requirements — matching area type, hello and dead timers, network type, stub flags, and authentication. Study show ip ospf neighbor states (INIT, 2-WAY, FULL). Then practise related 350-401 OSPF questions on adjacency and route selection.
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?
OSPF neighbours must agree on key parameters.
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Last reviewed: Jun 18, 2026
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