The answer is that the telemetry subscription is missing the 'source-interface' configuration. When troubleshooting telemetry no data received, the most likely cause on a Cisco IOS-XE router is that the dial-out subscription lacks a source-interface, which forces the router to use an unpredictable IP address that the collector may not recognize or route back to. Even though the collector is reachable and gRPC dial-out is configured correctly, without a specified source-interface, the router cannot establish a consistent TCP session for streaming operational data from YANG models like Cisco-IOS-XE-process-cpu-oper. On the ENCOR 350-401 exam, this tests your understanding that model-driven telemetry subscriptions for operational data require explicit source addressing to ensure the collector receives the stream. A common trap is assuming reachability alone guarantees data flow, but the source-interface is mandatory for dial-out telemetry to bind the connection to a specific interface. Memory tip: "No source, no course"—always specify the source-interface for dial-out subscriptions.
350-401 Model-Driven Telemetry Practice Question
This 350-401 practice question tests your understanding of model-driven telemetry. 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 engineer is configuring model-driven telemetry on a Cisco IOS-XE router to stream CPU and memory statistics to a collector. The engineer wants to use the YANG model 'Cisco-IOS-XE-process-cpu-oper' and 'Cisco-IOS-XE-memory-oper'. After configuring the telemetry subscription, the engineer notices that no data is being received at the collector. The collector is reachable and the gRPC dial-out is configured correctly. What is the most likely cause of the issue?
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 telemetry subscription is missing the 'source-interface' configuration
The correct answer is that the YANG models are operational data models and require the 'source-address' to be specified under the telemetry receiver, or the subscription must be for operational data. Actually, the most likely cause is that the engineer did not include the 'source-interface' configuration under the telemetry subscription, which is required for dial-out telemetry to ensure the router uses the correct IP address. The other options are incorrect because the collector is reachable, so firewall is not the issue; YANG models are correct; and gRPC is supported.
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 YANG models specified are not supported on IOS-XE
Why it's wrong here
Both 'Cisco-IOS-XE-process-cpu-oper' and 'Cisco-IOS-XE-memory-oper' are supported on IOS-XE.
✓
The telemetry subscription is missing the 'source-interface' configuration
Why this is correct
Without a source-interface, the router may use an unreachable IP address, causing the collector to drop the connection or not receive data.
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 collector is blocking UDP traffic from the router
Why it's wrong here
gRPC uses TCP, not UDP, so UDP blocking is irrelevant.
✗
The engineer must enable 'ip http secure-server' for telemetry to work
Why it's wrong here
HTTP secure-server is not required for gRPC telemetry; it is used for RESTCONF.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Detailed technical explanation
How to think about this question
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
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.
Use explanations to understand the rule behind the answer.
TExam Day Tips
→Underline the problem statement mentally.
→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.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this 350-401 question in full detail.
Identify which 350-401 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
Model-Driven Telemetry — This question tests Model-Driven Telemetry — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The telemetry subscription is missing the 'source-interface' configuration — The correct answer is that the YANG models are operational data models and require the 'source-address' to be specified under the telemetry receiver, or the subscription must be for operational data. Actually, the most likely cause is that the engineer did not include the 'source-interface' configuration under the telemetry subscription, which is required for dial-out telemetry to ensure the router uses the correct IP address. The other options are incorrect because the collector is reachable, so firewall is not the issue; YANG models are correct; and gRPC is supported.
What should I do if I get this 350-401 question wrong?
Identify which 350-401 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
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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