The answer is that the JSON payload is missing a required field, specifically the 'type' leaf under the interface. This is correct because the ietf-interfaces YANG model defines the 'type' leaf as mandatory; without it, the device cannot complete the interface configuration even though the RESTCONF API returns a 201 Created status. The 201 response only confirms the resource container was created, not that all mandatory child nodes were provided. On the ENCOR 350-401 exam, this tests your understanding that RESTCONF success codes do not guarantee full operational configuration—a common trap is assuming 201 means the interface is fully functional. Remember that YANG models enforce mandatory fields at the data model level, not the API response level. Memory tip: "201 is just the envelope, not the letter inside"—always verify mandatory leaves like 'type' and 'enabled' for interface configuration.
CCNP Automation Practice Question
This 350-401 practice question tests your understanding of 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.
Refer to the exhibit. A Python script sends the JSON payload shown via a POST request to the RESTCONF URI /restconf/data/ietf-interfaces:interfaces on a Cisco IOS XE device. The API returns 201 Created, but the interface GigabitEthernet1 is not configured. What is the most likely cause?
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 payload is missing a required field for the interface
The 201 Created response indicates the RESTCONF request was accepted and the resource was created, but the interface GigabitEthernet1 is not configured because the JSON payload is missing a required field. In the ietf-interfaces YANG model, the 'type' leaf under an interface is mandatory; without it, the device cannot complete the interface configuration, even though the API returns a success status for the creation of the container.
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 script is not authenticated
Why it's wrong here
201 indicates successful authentication.
✗
The URI should be /restconf/data/ietf-interfaces:interfaces/interface=GigabitEthernet1
Why it's wrong here
The URI is correct for creating a new resource.
✓
The payload is missing a required field for the interface
Why this is correct
The model may require a description.
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.
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misconception that a 201 Created status guarantees full configuration success, when in reality the YANG model's mandatory fields must be included in the payload for the interface to be operational.
Detailed technical explanation
How to think about this question
The ietf-interfaces YANG model (RFC 7223) defines the 'type' leaf as mandatory (mandatory true) under the 'interface' list entry, typically using an identity such as 'iana-if-type:ethernetCsmacd'. When a POST request creates the interface container but omits this required leaf, the device may accept the creation of the empty container but fail to apply the interface configuration, leaving the interface in a non-operational state. This behavior is distinct from a strict schema validation error, as RESTCONF can accept partial data and defer enforcement to the device's internal logic.
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 practitioner preparing for the 350-401 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
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.
Automation — This question tests Automation — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The payload is missing a required field for the interface — The 201 Created response indicates the RESTCONF request was accepted and the resource was created, but the interface GigabitEthernet1 is not configured because the JSON payload is missing a required field. In the ietf-interfaces YANG model, the 'type' leaf under an interface is mandatory; without it, the device cannot complete the interface configuration, even though the API returns a success status for the creation of the container.
What should I do if I get this 350-401 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.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
This 350-401 practice question is part of Courseiva's free Cisco certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 350-401 exam.
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.