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 large enterprise uses Cisco DNA Center to manage their campus network. They have deployed fabric technology for SD-Access. The network team wants to use the DNA Center REST API to automate the addition of new wireless users to a specific virtual network (VN) based on their location (building). They have identified the API endpoint for creating a user device in the fabric. However, when they send a POST request with the appropriate JSON body, they receive a 400 Bad Request error. The JSON payload includes the mandatory fields for hostname, MAC address, and VN name. What is the most likely cause of the error?
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 the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The virtual network name provided does not exist in the fabric.
The 400 Bad Request error indicates that the server cannot process the request due to a client-side issue, such as invalid data in the payload. Since the mandatory fields (hostname, MAC address, VN name) are provided, the most likely cause is that the virtual network (VN) name does not match any existing VN in the fabric. DNA Center validates the VN name against its fabric configuration; if the VN is not defined, the API rejects the request with a 400 error.
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 API call requires an authentication token that is missing or expired.
Why it's wrong here
This would result in a 401 Unauthorized error, not 400.
✓
The virtual network name provided does not exist in the fabric.
Why this is correct
If the VN doesn't exist, the API returns a 400 error.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
The MAC address format is incorrect (e.g., lowercase vs uppercase).
Why it's wrong here
DNA Center typically normalizes MAC formats, so this is less likely.
✗
The user making the API call does not have sufficient privileges.
Why it's wrong here
Insufficient privileges would return a 403 Forbidden error.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the distinction between HTTP status codes (400 vs 401 vs 403) to see if candidates understand that 400 errors are client-side payload issues, not authentication or authorization problems.
Detailed technical explanation
How to think about this question
In Cisco DNA Center, fabric virtual networks (VNs) are defined as part of the SD-Access fabric deployment. When creating a user device via the REST API, the VN name must exactly match an existing VN in the fabric's 'Virtual Network' configuration. DNA Center performs a lookup against the fabric database; if the VN is not found, the API returns a 400 error with a descriptive message. This validation ensures that devices are only added to valid network segments, preventing misconfiguration.
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 junior network technician can log in to a core router but cannot reach the enable prompt or configuration mode. The AAA server is authenticating the login — but the authorisation policy only grants privilege level 1, not 15. Authentication (who you are) is working; authorisation (what you can do) is not.
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 virtual network name provided does not exist in the fabric. — The 400 Bad Request error indicates that the server cannot process the request due to a client-side issue, such as invalid data in the payload. Since the mandatory fields (hostname, MAC address, VN name) are provided, the most likely cause is that the virtual network (VN) name does not match any existing VN in the fabric. DNA Center validates the VN name against its fabric configuration; if the VN is not defined, the API rejects the request with a 400 error.
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: "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?
Read the scenario before looking for a memorised answer.
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