Question 969 of 2,015

REST APIs and Data Models →mediumMultiple ChoiceObjective-mapped

Quick Answer

The answer is that the engineer should have used POST instead of PUT to create a new VLAN list entry. In RESTCONF, PUT is designed to create or replace a specific resource at a known URI, but when adding a new entry to a YANG list—such as a VLAN within the VlanList—the POST method is required because the list entry does not yet exist and its key value is unknown to the server. This distinction is a common trap on the ENCOR 350-401 exam, which tests your understanding of RESTCONF resource operations and HTTP method semantics; many candidates mistakenly assume PUT works for all creation tasks. The 405 Method Not Allowed error directly signals that the server recognized the URI but rejected the method for that resource type. Remember the memory tip: “PUT for a known spot, POST for a brand-new slot.”

350-401 REST APIs and Data Models Practice Question

This 350-401 practice question tests your understanding of rest apis and data models. 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 engineer is automating the configuration of a new VLAN on a Cisco Catalyst 9000 switch using RESTCONF. The engineer sends a PUT request to the URI 'https://switch/restconf/data/Cisco-NX-OS-device:Native/VlanList' with a JSON payload containing the VLAN details. The switch responds with a 405 Method Not Allowed error. What is the most likely cause of this error?

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.

Question 1mediummultiple choice

Open the full VLAN trunking answer →

A
The engineer used the wrong URI; the correct URI should include a specific VLAN ID.
Why wrong: Incorrect because the URI for creating a new list entry does not require a specific ID; the POST method is used to add an entry to the list.
B
The engineer should have used the POST method instead of PUT to create a new list entry.
Correct because RESTCONF uses POST to create a new resource in a list, while PUT is used to replace an existing resource.
C
The payload format is incorrect; the engineer must use XML instead of JSON.
Why wrong: Incorrect because RESTCONF supports both JSON and XML; the format is not the cause of a 405 error.
D
The switch does not support RESTCONF for VLAN configuration; NETCONF must be used instead.
Why wrong: Incorrect because Cisco Catalyst 9000 switches support RESTCONF for VLAN configuration; the error is method-related.

Full breakdown with real-world context →

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 engineer should have used the POST method instead of PUT to create a new list entry.

The PUT method is typically used to create or replace a resource, but for list entries in RESTCONF, the POST method is used to add a new entry. The 405 error indicates that the method is not allowed for the specified URI. The engineer should use POST to add a new VLAN entry to the list.

Key principle: A trunk being up does not mean the VLAN is allowed across it. Always verify the allowed VLAN list and whether the VLAN exists on both switches.

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 engineer used the wrong URI; the correct URI should include a specific VLAN ID.
Why it's wrong here
Incorrect because the URI for creating a new list entry does not require a specific ID; the POST method is used to add an entry to the list.
✓
The engineer should have used the POST method instead of PUT to create a new list entry.
Why this is correct
Correct because RESTCONF uses POST to create a new resource in a list, while PUT is used to replace an existing resource.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Access ports place end devices into a single VLAN.
✗
The payload format is incorrect; the engineer must use XML instead of JSON.
Why it's wrong here
Incorrect because RESTCONF supports both JSON and XML; the format is not the cause of a 405 error.
✗
The switch does not support RESTCONF for VLAN configuration; NETCONF must be used instead.
Why it's wrong here
Incorrect because Cisco Catalyst 9000 switches support RESTCONF for VLAN configuration; the error is method-related.

Common exam traps

Common exam trap: an active trunk can still block the VLAN you need

A trunk being up does not prove every VLAN is crossing it. Check allowed VLAN lists, native VLAN mismatch, VLAN existence and access-port assignment.

Detailed technical explanation

How to think about this question

VLAN questions usually combine access-port and trunking clues. The key is to identify whether the issue is local to one switchport, caused by the trunk, or caused by the VLAN not existing where it needs to exist.

KKey Concepts to Remember

Access ports place end devices into a single VLAN.
Trunk ports carry multiple VLANs between switches.
Allowed VLAN lists decide which VLANs can cross a trunk.
Native VLAN mismatch can create confusing symptoms.

TExam Day Tips

Use show vlan brief to verify access VLANs.
Use show interfaces trunk to verify trunk state and allowed VLANs.
Do not treat every same-VLAN issue as a routing problem.

Key takeaway

A trunk being up does not mean the VLAN is allowed across it. Always verify the allowed VLAN list and whether the VLAN exists on both switches.

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.

Review VLAN allowed lists, native VLAN mismatch detection, and how to verify VLAN membership with show vlan brief and show interfaces trunk. Then practise related 350-401 questions on switching, trunking, and access-port configuration.

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FAQ

Questions learners often ask

What does this 350-401 question test?

REST APIs and Data Models — This question tests REST APIs and Data Models — Access ports place end devices into a single VLAN..

What is the correct answer to this question?

The correct answer is: The engineer should have used the POST method instead of PUT to create a new list entry. — The PUT method is typically used to create or replace a resource, but for list entries in RESTCONF, the POST method is used to add a new entry. The 405 error indicates that the method is not allowed for the specified URI. The engineer should use POST to add a new VLAN entry to the list.

What should I do if I get this 350-401 question wrong?

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?

Access ports place end devices into a single VLAN.

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