200-901 Understanding and Using APIs Practice Question
A developer is using gRPC/gNMI for model-driven telemetry from a Cisco device. Which of the following best describes the difference between dial-in and dial-out streaming?
⚠ Common exam trap
200-901 often tests the initiator direction in telemetry modes, tricking candidates who assume the collector always initiates (as in traditional SNMP polling).
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
✓
Dial-in is initiated by the collector; dial-out is initiated by the device.
In dial-in telemetry, the collector (management station) initiates the connection to the network device and subscribes to telemetry data — the collector 'dials in' to the device. In dial-out telemetry, the network device initiates the connection to the collector and pushes data, which is useful when the device is behind NAT or a firewall.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Dial-in uses gNMI; dial-out uses NETCONF.
Why it's wrong here
Dial-in and dial-out describe which side initiates the gRPC/gNMI session, not which protocol is used; both directions employ gNMI over gRPC. NETCONF is a separate configuration protocol. Dial-in suits a collector polling devices, while dial-out suits devices pushing telemetry to a collector.
- ✗
Dial-in uses TCP; dial-out uses UDP.
Why it's wrong here
Both modes run gNMI over gRPC, which uses HTTP/2 over TCP; UDP is not involved. TCP would be the answer only if the question asked about a UDP-based telemetry export such as IPFIX, not gRPC streaming.
- ✗
Dial-in is initiated by the network device; dial-out is initiated by the collector.
Why it's wrong here
The direction is inverted: dial-in has the collector initiate the session to the device, while dial-out has the device initiate to the collector. The option describes the reverse, which would be the case only if the roles of initiator were swapped.
- ✓
Dial-in is initiated by the collector; dial-out is initiated by the device.
Why this is correct
In dial-in telemetry the collector opens the gRPC session to the device and subscribes; in dial-out the device initiates the connection to the collector and pushes data. This direction of session initiation is the defining difference between the two modes.
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JA
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 200-901 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 200-901 exam.