This 200-901 practice question tests your understanding of infrastructure and automation. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A network automation engineer is writing an Ansible playbook to configure interface descriptions on Cisco IOS-XE devices. The playbook uses the ios_config module. Which attribute should be used to ensure idempotency and only apply changes when the interface does not already have the desired description?
lines
lines defines the configuration lines to be added or modified; the module checks current state to avoid duplicate changes.
src
Why wrong: src is used to specify a source file, not inline lines.
parents
Why wrong: parents defines the parent context (e.g., interface), but alone does not ensure idempotency.
before
Why wrong: before is used to specify commands to run before changes, not for idempotent configuration.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
lines
Option A is correct because the `lines` attribute in the `ios_config` module specifies the exact configuration lines to be applied. Ansible's `ios_config` module inherently checks the current device configuration against the desired state defined in `lines`; if the interface already has the matching description, the module skips the task, ensuring idempotency. This prevents unnecessary configuration changes and maintains network stability.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
lines
Why this is correct
lines defines the configuration lines to be added or modified; the module checks current state to avoid duplicate changes.
Related concept
Read the scenario before looking for a memorised answer.
src
Why it's wrong here
src is used to specify a source file, not inline lines.
parents
Why it's wrong here
parents defines the parent context (e.g., interface), but alone does not ensure idempotency.
before
Why it's wrong here
before is used to specify commands to run before changes, not for idempotent configuration.
Common exam traps
Cisco often tests the misconception that `src` or `parents` alone provide idempotency, but the trap here is that `lines` is the attribute that directly enables the module to compare and skip unchanged configuration lines, while `parents` only sets the configuration context and does not perform the idempotency check itself.
Trap categories for this question
Command / output trap
before is used to specify commands to run before changes, not for idempotent configuration.
Detailed technical explanation
Under the hood, the `ios_config` module uses the `show running-config` output to compare the desired `lines` against the current configuration. If the exact line (e.g., `description Uplink to Core`) already exists under the specified `parents` context, the module reports `ok` with no changes. This is similar to Ansible's `network_cli` connection method leveraging NAPALM or native CLI parsing to achieve declarative state management. In a real-world scenario, using `lines` without `parents` on a global context could accidentally apply the description to all interfaces if not scoped correctly, so `parents` is often used alongside `lines` to target a specific interface.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A practitioner preparing for the 200-901 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
What to study next
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FAQ
Infrastructure and Automation — This question tests Infrastructure and Automation — Read the scenario before looking for a memorised answer..
The correct answer is: lines — Option A is correct because the `lines` attribute in the `ios_config` module specifies the exact configuration lines to be applied. Ansible's `ios_config` module inherently checks the current device configuration against the desired state defined in `lines`; if the interface already has the matching description, the module skips the task, ensuring idempotency. This prevents unnecessary configuration changes and maintains network stability.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 24, 2026
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