350-501 Automation and Assurance Practice Question
A network operator uses gRPC Network Management Interface (gNMI) to collect telemetry data from routers. They notice that some updates are missing. Which gNMI mode should be used to ensure that all state changes are captured?
⚠ Common exam trap
Cisco often tests the misconception that SAMPLE mode with a very short interval is sufficient to capture all changes, but the trap is that SAMPLE can still miss state changes that occur and revert between samples, whereas ON_CHANGE guarantees delivery of every transition.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
ON_CHANGE
ON_CHANGE mode in gNMI ensures that the target device sends a telemetry update immediately whenever a state change occurs, guaranteeing that no updates are missed. This is in contrast to SAMPLE mode, which only sends periodic snapshots and can miss transient changes between intervals. Therefore, to capture all state changes, ON_CHANGE is the correct subscription mode.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
ON_CHANGE
Why this is correct
Sends updates only when a value changes, capturing all changes.
- ✗
TARGET_DEFINED
Why it's wrong here
Not a standard gNMI mode.
- ✗
POLL
Why it's wrong here
Polling is not a gNMI subscription mode.
- ✗
SAMPLE
Why it's wrong here
Periodic sampling may miss changes between intervals.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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