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 network administrator is managing a small office with 10 Cisco 9200 switches. They want to automate the deployment of a standard base configuration (VLANs, STP, management access) to all switches. They have a Linux server with Ansible installed. The administrator writes a playbook that uses the 'ios_config' module to apply configuration blocks. However, when they run the playbook against the first switch, it fails with an authentication error. The administrator can SSH to the switch manually using the same credentials. What is the most likely cause of the failure?
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 Ansible playbook is missing the 'ansible_connection: network_cli' and 'ansible_network_os: ios' variables.
For Ansible to connect to network devices, the connection type must be set to 'network_cli' and the network OS must be specified. Without these, Ansible may attempt to use the default SSH connection method (paramiko) which does not handle network device prompts correctly, leading to authentication errors.
Key principle: A trunk being up does not mean the VLAN is allowed across it. Always verify the allowed VLAN list and whether the VLAN exists on both switches.
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 playbook is missing the 'ansible_connection: network_cli' and 'ansible_network_os: ios' variables.
Why this is correct
Network devices require these variables to handle the SSH session correctly.
Clue confirmation
The clue words "first", "most likely" in the question point toward this answer.
Related concept
Access ports place end devices into a single VLAN.
✗
The switch's SSH server does not support the key exchange algorithm used by Ansible.
Why it's wrong here
This would cause a different error (key exchange failure) not authentication.
✗
The playbook is using the wrong username because the variable is not defined.
Why it's wrong here
If credentials are correct for manual SSH, they are likely correct in the playbook.
✗
The switch is running an incompatible IOS version that does not support the commands in the playbook.
Why it's wrong here
Incompatible commands would cause command errors, not authentication errors.
Common exam traps
Common exam trap: an active trunk can still block the VLAN you need
A trunk being up does not prove every VLAN is crossing it. Check allowed VLAN lists, native VLAN mismatch, VLAN existence and access-port assignment.
Trap categories for this question
Command / output trap
Incompatible commands would cause command errors, not authentication errors.
Detailed technical explanation
How to think about this question
VLAN questions usually combine access-port and trunking clues. The key is to identify whether the issue is local to one switchport, caused by the trunk, or caused by the VLAN not existing where it needs to exist.
KKey Concepts to Remember
Access ports place end devices into a single VLAN.
Trunk ports carry multiple VLANs between switches.
Allowed VLAN lists decide which VLANs can cross a trunk.
Native VLAN mismatch can create confusing symptoms.
TExam Day Tips
→Use show vlan brief to verify access VLANs.
→Use show interfaces trunk to verify trunk state and allowed VLANs.
→Do not treat every same-VLAN issue as a routing problem.
Key takeaway
A trunk being up does not mean the VLAN is allowed across it. Always verify the allowed VLAN list and whether the VLAN exists on both switches.
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.
Review VLAN allowed lists, native VLAN mismatch detection, and how to verify VLAN membership with show vlan brief and show interfaces trunk. Then practise related 200-901 questions on switching, trunking, and access-port configuration.
Infrastructure and Automation — This question tests Infrastructure and Automation — Access ports place end devices into a single VLAN..
What is the correct answer to this question?
The correct answer is: The Ansible playbook is missing the 'ansible_connection: network_cli' and 'ansible_network_os: ios' variables. — For Ansible to connect to network devices, the connection type must be set to 'network_cli' and the network OS must be specified. Without these, Ansible may attempt to use the default SSH connection method (paramiko) which does not handle network device prompts correctly, leading to authentication errors.
What should I do if I get this 200-901 question wrong?
Review VLAN allowed lists, native VLAN mismatch detection, and how to verify VLAN membership with show vlan brief and show interfaces trunk. Then practise related 200-901 questions on switching, trunking, and access-port configuration.
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?
Access ports place end devices into a single VLAN.
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