The answer is that the ios_config module is not configured to replace the existing configuration. By default, the ios_config module appends commands to the running configuration rather than replacing them, so when you attempt to change an IP address on Loopback100, the new IP command is added while the old address remains active. Cisco IOS allows multiple IP addresses on a single interface only when the secondary keyword is used, but the module does not automatically apply this keyword, leaving the original address intact. On the ENCOR 350-401 exam, this tests your understanding of how Ansible interacts with Cisco IOS configuration modes, specifically the difference between set and replace operations. A common trap is assuming that sending a new IP command overwrites the old one, but without the replace option or a before/parents directive to remove the old address first, the change fails silently. Remember: Ansible appends, it does not overwrite—think "add, not swap" for interface IP changes.
CCNP Automation Practice Question
This 350-401 practice question tests your understanding of 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.
Exhibit
R1#show ip interface brief | include Loopback
Loopback0 10.1.1.1 YES manual up up
Loopback100 10.1.100.1 YES manual up up
R1#show run interface Loopback100
Building configuration...
Current configuration : 67 bytes
!
interface Loopback100
ip address 10.1.100.1 255.255.255.0
end
R1#show run | include snmp-server
snmp-server community public RO
snmp-server community private RW
Refer to the exhibit. A network engineer wants to use Ansible to change the IP address of Loopback100 from 10.1.100.1/24 to 10.1.200.1/24. The playbook uses the ios_config module. The playbook runs successfully, but the IP address remains unchanged. What is the most likely reason?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
R1#show ip interface brief | include Loopback
Loopback0 10.1.1.1 YES manual up up
Loopback100 10.1.100.1 YES manual up up
R1#show run interface Loopback100
Building configuration...
Current configuration : 67 bytes
!
interface Loopback100
ip address 10.1.100.1 255.255.255.0
end
R1#show run | include snmp-server
snmp-server community public RO
snmp-server community private RW
A
The loopback interface is administratively down
Why wrong: The interface is up.
B
The playbook is sending the wrong CLI commands
Why wrong: The commands appear correct.
C
The ios_config module is not configured to replace the existing configuration
Without replace/match, Ansible may not apply the change.
D
The SNMP community strings are not configured correctly
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The ios_config module is not configured to replace the existing configuration
The ios_config module in Ansible, by default, uses a 'set' operation that appends commands to the running configuration. To change an existing IP address on an interface, the module must be configured with the 'replace' option or use a 'before'/'parents' directive to remove the old address first. Without this, the new IP command is added but the old one remains, and the interface retains the original address because Cisco IOS allows multiple IP addresses on a single interface only if the secondary keyword is used, which the module does not automatically apply.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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 loopback interface is administratively down
Why it's wrong here
The interface is up.
✗
The playbook is sending the wrong CLI commands
Why it's wrong here
The commands appear correct.
✓
The ios_config module is not configured to replace the existing configuration
Why this is correct
Without replace/match, Ansible may not apply the change.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
The SNMP community strings are not configured correctly
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misconception that the ios_config module is idempotent by default for all configuration changes, when in reality it only ensures the specified lines are present, not that conflicting lines are removed.
Trap categories for this question
Command / output trap
The commands appear correct.
Detailed technical explanation
How to think about this question
The ios_config module uses the 'cli_command' or 'cli_config' transport to send configuration commands to the device. By default, it operates in 'append' mode, meaning it adds the specified lines to the configuration without removing conflicting lines. To replace an existing IP address, the module must be used with the 'replace' parameter set to 'block' or 'line', or the playbook must explicitly include a 'no ip address' command before the new one. This is a common pitfall because the module's idempotency does not extend to removing pre-existing configuration lines unless told to do so.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A practitioner preparing for the 350-401 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
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Automation — This question tests Automation — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The ios_config module is not configured to replace the existing configuration — The ios_config module in Ansible, by default, uses a 'set' operation that appends commands to the running configuration. To change an existing IP address on an interface, the module must be configured with the 'replace' option or use a 'before'/'parents' directive to remove the old address first. Without this, the new IP command is added but the old one remains, and the interface retains the original address because Cisco IOS allows multiple IP addresses on a single interface only if the secondary keyword is used, which the module does not automatically apply.
What should I do if I get this 350-401 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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