200-901 Infrastructure and Automation Practice Question
This 200-901 practice question tests your understanding of infrastructure and automation. 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 DevOps team uses Ansible to configure Cisco Nexus switches for a new data center. They have a playbook that uses the nxos_vlan module to create VLANs and nxos_interface module to assign access VLANs. The playbook runs successfully on the first Nexus switch but fails on the second with error: 'module_stderr: ntclib: error: unable to connect to switch'. Both switches are reachable via ping and SSH from the Ansible control node. The inventory file has the same SSH credentials for both switches. What is the most likely cause of the connection failure on the second switch?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "first"
Why it matters: Order matters here. You are being tested on which action comes before the others — not which action is generally useful.
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 second switch does not have NX-API enabled.
The error 'module_stderr: ntclib: error: unable to connect to switch' indicates that the Ansible nxos modules are attempting to use NX-API (REST-like HTTP/HTTPS API) to communicate with the switch, not SSH. Even though SSH is reachable, the second switch likely has NX-API disabled or not configured, causing the connection failure. The nxos_vlan and nxos_interface modules in Ansible rely on NX-API by default when the connection type is set to 'network_cli' or 'httpapi', and without NX-API enabled, the modules cannot execute.
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 second switch does not have NX-API enabled.
Why this is correct
The error indicates NX-API connection failure; enabling NX-API resolves.
Clue confirmation
The clue words "first", "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
The Ansible control node has an incompatible version of the nxos collection.
Why it's wrong here
Collection version would affect both switches equally if same playbook.
✗
The second switch has a different VLAN database that conflicts with the playbook.
Why it's wrong here
VLAN database conflict would produce configuration error, not connection failure.
✗
The second switch's SSH key fingerprint has changed and is not accepted.
Why it's wrong here
SSH key issue would cause different error, not ntclib connection error.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misconception that Ansible nxos modules use SSH for all operations, when in fact they default to NX-API for task execution, so candidates may overlook the need for NX-API to be enabled on the target switch.
Detailed technical explanation
How to think about this question
NX-API is a Cisco NX-OS feature that exposes a RESTful API over HTTP/HTTPS, allowing automation tools like Ansible to send CLI commands via structured JSON or XML payloads. It must be explicitly enabled with the 'feature nxapi' command and configured with a port (e.g., 'nxapi http port 80'). Ansible's nxos modules default to using NX-API when the ansible_connection is set to 'httpapi' or 'network_cli' with the nxos platform, and if NX-API is not enabled, the ntclib library fails to establish a TCP connection to the API port, producing the exact error seen.
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.
Infrastructure and Automation — This question tests Infrastructure and Automation — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The second switch does not have NX-API enabled. — The error 'module_stderr: ntclib: error: unable to connect to switch' indicates that the Ansible nxos modules are attempting to use NX-API (REST-like HTTP/HTTPS API) to communicate with the switch, not SSH. Even though SSH is reachable, the second switch likely has NX-API disabled or not configured, causing the connection failure. The nxos_vlan and nxos_interface modules in Ansible rely on NX-API by default when the connection type is set to 'network_cli' or 'httpapi', and without NX-API enabled, the modules cannot execute.
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.
Are there clue words in this question I should notice?
Yes — watch for: "first", "most likely". Order matters here. You are being tested on which action comes before the others — not which action is generally useful.
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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