350-401 Automation Practice Question
A network engineer is using a Python script with the ncclient library to retrieve interface statistics from a Cisco IOS XE router. The script connects successfully, but when it sends a <get> RPC, the router returns an error stating that the requested data model is not supported. The engineer verifies that the YANG model is present on the device. What is the most likely cause of this error?
⚠ Common exam trap
The trap here is assuming that the presence of a YANG file on the device automatically makes it available via NETCONF, when in fact it must be advertised as a capability.
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
✓
The YANG model is present but not enabled in the NETCONF capability set on the device.
The error indicates that the NETCONF server does not support the requested YANG model, even though the model file exists. In NETCONF, capabilities are advertised in the initial <hello> exchange. If a model is not listed there, it is not enabled for NETCONF access. The engineer must verify the device's NETCONF capabilities and ensure the model is supported and enabled.
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 using the wrong NETCONF port; it should use port 830 instead of 22.
Why it's wrong here
NETCONF over SSH typically uses port 830, but if the connection succeeded and an RPC was sent, the port is correct. The error is related to the data model, not the transport. Using port 22 might work if NETCONF is configured on that port, but the error would not be about data model support.
- ✗
The NETCONF session is using the default namespace urn:ietf:params:xml:ns:netconf:base:1.0 instead of the correct YANG namespace.
Why it's wrong here
The default NETCONF namespace is used for the RPC envelope, not for the data being requested. The error indicates the data model itself is not supported, not a namespace issue with the RPC. The engineer would still receive a valid response if the YANG model were correctly referenced. This option misidentifies the root cause.
- ✗
The ncclient library version is incompatible with the router's NETCONF implementation.
Why it's wrong here
While library incompatibilities can cause errors, they typically manifest as connection or parsing failures, not as a specific 'data model not supported' error from the router. The error is generated by the NETCONF server on the device, indicating it does not recognize the requested data model, independent of the client library version.
- ✓
The YANG model is present but not enabled in the NETCONF capability set on the device.
Why this is correct
For a YANG model to be accessible via NETCONF, it must be advertised in the device's NETCONF capabilities. Even if the model file exists, if it is not enabled or supported by the NETCONF server, requests will fail. The engineer should check the <hello> message for the model's namespace and revision. This is the most likely cause of the error.
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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
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