The answer is that the engineer is viewing a different switch or the configuration was reverted by another process. This is correct because the NX-API command 'switchport trunk allowed vlan add 40' executed successfully, as confirmed by the script logs, and the running config already shows VLAN 40 present in the allowed list—meaning the change was applied. The discrepancy arises not from a command failure, but from a mismatch between the device where the config was applied and the device being inspected, or from an automated rollback or competing script reverting the change before the show command was run. On the Cisco DCCOR 350-601 exam, this scenario tests your understanding of NX-API behavior and the importance of verifying the target device identity, especially in automated environments where multiple switches or configuration management tools are in play. A common trap is assuming a successful API response guarantees the config is visible on the console you are using. Memory tip: “API success does not equal console truth—verify your target.”
350-601 Automation Practice Question
This 350-601 practice question tests your understanding of automation. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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
Refer to the exhibit.
interface Eth1/1
description Server-Connection
switchport mode access
switchport access vlan 100
spanning-tree port type edge
no shutdown
interface Eth1/2
description Trunk-to-Core
switchport mode trunk
switchport trunk allowed vlan 10,20,30
spanning-tree port type network
no shutdown
Refer to the exhibit. An automation script is used to configure a new VLAN 40 on Eth1/2 trunk. The script sends the following NX-API command: 'switchport trunk allowed vlan add 40'. After execution, the engineer runs 'show running-config interface eth1/2' and sees that the trunk allowed VLAN list shows '10,20,30,40'. However, the automation script logs indicate success for adding VLAN 40, but the running config does not show the change. What is the most likely issue?
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.
Refer to the exhibit.
interface Eth1/1
description Server-Connection
switchport mode access
switchport access vlan 100
spanning-tree port type edge
no shutdown
interface Eth1/2
description Trunk-to-Core
switchport mode trunk
switchport trunk allowed vlan 10,20,30
spanning-tree port type network
no shutdown
A
The command syntax is incorrect; 'add' is not a valid keyword.
Why wrong: The 'add' keyword is valid for adding VLANs to the allowed list.
B
The engineer is viewing a different switch or the configuration was reverted by another process.
The running config shows the change, so the issue is likely that the engineer is looking at the wrong device or the config was changed after.
C
The script actually removed the existing VLANs and replaced them with only VLAN 40.
Why wrong: The running config shows the list includes all VLANs, so it was not replaced.
D
The NX-API command was sent to the wrong interface.
Why wrong: The command targeted Eth1/2, and the running config shows that interface.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The engineer is viewing a different switch or the configuration was reverted by another process.
Option B is correct because the running config shows VLANs 10,20,30,40, indicating that VLAN 40 was successfully added. The script logs confirm success, so the command syntax and interface target are correct. The discrepancy between the logs and the running config is most likely due to the engineer viewing a different switch (e.g., a management console pointing to a different device) or the configuration being reverted by another process (e.g., a configuration rollback or a competing automation script).
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 command syntax is incorrect; 'add' is not a valid keyword.
Why it's wrong here
The 'add' keyword is valid for adding VLANs to the allowed list.
✓
The engineer is viewing a different switch or the configuration was reverted by another process.
Why this is correct
The running config shows the change, so the issue is likely that the engineer is looking at the wrong device or the config was changed after.
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 script actually removed the existing VLANs and replaced them with only VLAN 40.
Why it's wrong here
The running config shows the list includes all VLANs, so it was not replaced.
✗
The NX-API command was sent to the wrong interface.
Why it's wrong here
The command targeted Eth1/2, and the running config shows that interface.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the candidate's ability to distinguish between a command that fails silently versus a command that succeeds but the result is not visible due to environmental factors (e.g., wrong device, configuration rollback), rather than a syntax or interface error.
Trap categories for this question
Keyword trap
The 'add' keyword is valid for adding VLANs to the allowed list.
Command / output trap
The running config shows the list includes all VLANs, so it was not replaced.
Detailed technical explanation
How to think about this question
NX-OS NX-API uses JSON-RPC over HTTP/HTTPS to send CLI commands; the 'switchport trunk allowed vlan add' command modifies the allowed VLAN list in the running configuration without affecting existing entries. Under the hood, the switch maintains a VLAN bitmap for the trunk interface, and the 'add' keyword performs a bitwise OR operation. In real-world scenarios, configuration drift can occur when multiple automation scripts or manual changes compete, or when the engineer's terminal session is not synchronized with the actual device state.
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 help-desk technician troubleshoots why a newly connected PC cannot reach shared printers on the same floor. The cable is good, the switch port is active, but the PC is in VLAN 20 and the printers are in VLAN 10. The uplink trunk only allows VLAN 10. A trunk being up does not mean every VLAN crosses it.
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 engineer is viewing a different switch or the configuration was reverted by another process. — Option B is correct because the running config shows VLANs 10,20,30,40, indicating that VLAN 40 was successfully added. The script logs confirm success, so the command syntax and interface target are correct. The discrepancy between the logs and the running config is most likely due to the engineer viewing a different switch (e.g., a management console pointing to a different device) or the configuration being reverted by another process (e.g., a configuration rollback or a competing automation script).
What should I do if I get this 350-601 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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