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350-401 Practice Question: Which three statements about gRPC and gNMI in the…
Which three statements about gRPC and gNMI in the context of model-driven telemetry are true? (Choose three.)
⚠ Common exam trap
350-401 often tests whether candidates conflate gNMI with NETCONF because both use YANG — the trap is assuming gNMI inherits NETCONF's transport or model restrictions, when in fact gNMI is pure gRPC/HTTP2/protobuf and supports both OpenConfig and native YANG paths.
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
✓
gRPC uses HTTP/2 as its transport protocol and Protocol Buffers as its interface definition language.
Option A is correct because gRPC is built on HTTP/2 for transport (providing multiplexed streams, flow control, and header compression) and uses Protocol Buffers as its IDL for defining services and messages. Option B is correct because gNMI is a gRPC-based protocol defined by OpenConfig that supports both telemetry subscriptions (Subscribe RPC) and configuration operations (Get, Set, Capabilities RPCs). Option E is correct because gNMI defines subscription modes including SAMPLE (periodic) and ON_CHANGE, allowing devices to stream updates either at fixed intervals or when values change. Option C is incorrect because gNMI subscriptions can use any YANG-modeled paths, including native vendor models, not only OpenConfig models. Option D is incorrect because gNMI operates directly over gRPC/HTTP/2 and does not rely on NETCONF for session establishment or encoding; it uses Protocol Buffers for encoding.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
gRPC uses HTTP/2 as its transport protocol and Protocol Buffers as its interface definition language.
Why this is correct
gRPC's transport is HTTP/2, enabling multiplexed streams over one connection, while Protocol Buffers define the service contract and serialise payloads compactly. This satisfies the stem's requirement for accurate model-driven telemetry statements, since gNMI itself is built as a gRPC service using these same mechanisms.
- ✓
gNMI (gRPC Network Management Interface) is a gRPC-based protocol that can be used for both telemetry and configuration operations.
Why this is correct
gNMI runs over gRPC and, unlike one-way telemetry streaming alone, exposes both subscribe (telemetry) and set (configuration) RPCs. This dual capability satisfies the stem's requirement that the protocol serve telemetry and configuration operations through a single model-driven interface.
- ✗
gNMI telemetry subscriptions can only use YANG paths from OpenConfig models.
Why it's wrong here
gNMI subscriptions accept any YANG-modelled path, including native vendor models, not only OpenConfig. It is tempting because OpenConfig models are the common, portable choice for vendor-neutral telemetry, but gNMI itself imposes no such restriction on the schema used.
- ✗
gNMI relies on NETCONF for session establishment and data encoding.
Why it's wrong here
gNMI runs over gRPC using HTTP/2 and Protocol Buffers, with no NETCONF dependency for sessions or encoding. It is tempting because NETCONF also carries YANG-modelled configuration and state, so the two are easily conflated, yet gNMI was designed precisely to replace that transport.
- ✓
gNMI supports both periodic and on-change telemetry subscriptions.
Why this is correct
gNMI's subscription model defines distinct modes: SAMPLE for periodic collection at a specified interval, and ON_CHANGE for event-driven updates pushed when a monitored leaf alters. This satisfies the stem's requirement for both subscription types, unlike gRPC transport alone, which carries the messages but does not itself define telemetry subscription semantics.
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Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Cisco exam blueprint
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.