CCNP Automation Practice Question
A network engineer is using Python with the ncclient library to configure a Cisco IOS XE device via NETCONF. The script connects successfully but receives an RPC error when trying to apply a candidate configuration. The engineer inspects the device capabilities and sees 'urn:ietf:params:netconf:capability:candidate:1.0' is NOT listed. What is the most likely reason for the failure?
⚠ Common exam trap
The trap here is assuming that a successful NETCONF connection implies full feature support, when in fact capabilities must be checked to confirm datastore and operation support.
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 device does not support the NETCONF candidate datastore, so candidate configuration operations cannot be used.
The NETCONF capabilities exchange advertises supported features. The candidate datastore capability indicates whether the device supports a candidate configuration that can be edited and committed. Without it, operations targeting the candidate datastore will fail. The engineer should verify capabilities before attempting candidate-based workflows and use the running datastore instead.
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 device does not support the NETCONF candidate datastore, so candidate configuration operations cannot be used.
Why this is correct
The absence of the 'candidate' capability in the NETCONF capabilities list means the device does not support the candidate datastore. NETCONF operations like edit-config with candidate target or commit will fail. The engineer must use the running datastore directly or enable candidate support if available.
- ✗
The device requires a YANG model to be loaded before candidate configuration can be used.
Why it's wrong here
YANG models define data structures and are always present for supported features; they do not need to be manually loaded to enable candidate datastore support. The candidate capability is a separate NETCONF feature that must be advertised by the device, independent of YANG model availability.
- ✗
The NETCONF session must use SSH version 2, but the device is using SSH version 1.
Why it's wrong here
NETCONF over SSH requires SSH version 2, but this is a connection-level issue that would prevent the session from establishing at all. The scenario states the script connects successfully, so SSH version is not the cause. The missing candidate capability is the definitive clue here.
- ✗
The ncclient library version is incompatible with the IOS XE NETCONF implementation.
Why it's wrong here
While library compatibility can cause issues, the specific error and missing capability indicate a device feature limitation, not a library problem. If ncclient were incompatible, the connection would likely fail entirely or produce different errors. The capabilities list is authoritative for supported features.
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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
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