200-901 Infrastructure and Automation Practice Question
A developer writes a Python script that uses ncclient to configure a loopback interface on a Cisco IOS XE router. The script calls edit_config against the candidate datastore and then exits without calling commit. The next day, the interface is missing from the running configuration. What is the most likely cause?
⚠ Common exam trap
The trap here is assuming that edit_config immediately changes the running configuration, when it only stages changes in the candidate datastore until a commit is issued.
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 candidate datastore was discarded because the session ended without a commit operation.
NETCONF separates candidate configuration from running configuration. Writing to the candidate datastore stages changes but does not activate them. Only a commit RPC copies the candidate contents to running. When the session ends without commit, the candidate is discarded, which explains the missing interface.
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 candidate datastore was discarded because the session ended without a commit operation.
Why this is correct
Changes written to the candidate datastore are not active until a commit is issued. When the NETCONF session closes without committing, the candidate datastore is discarded and the running configuration remains unchanged. This precisely explains why the interface disappeared the next day.
- ✗
The running configuration was overwritten by a scheduled job that removed all loopback interfaces.
Why it's wrong here
There is no evidence of a scheduled job in the scenario, and inventing one is not justified. The described behavior is the expected outcome of editing the candidate datastore without committing, so an external job is an unnecessary and unsupported explanation.
- ✗
The edit_config operation requires a confirmed-commit timer to persist changes to the running datastore.
Why it's wrong here
confirmed-commit is an optional capability that allows a commit to be automatically rolled back unless confirmed within a timeout. It is not required for changes to persist. A normal commit is sufficient; the problem here is that no commit was issued at all.
- ✗
The device rejected the edit_config because loopback interfaces require a separate YANG module.
Why it's wrong here
Loopback interfaces are standard and supported by the ietf-interfaces and Cisco-specific YANG modules. The edit_config call likely succeeded against the candidate datastore. The absence of the interface is due to the missing commit, not module support or rejection.
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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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