Question 358 of 505

Network Fundamentals →hardMultiple ChoiceObjective-mapped

200-901 Network Fundamentals Practice Question

This 200-901 practice question tests your understanding of network fundamentals. 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.

A network automation engineer is using a Python script with the requests library to configure VLAN 100 on a Cisco Catalyst 9300 switch via the REST API. The script sends a PUT request to https://switch-ip/restconf/data/Cisco-IOS-XE-native:native/vlan. The response returns a 201 Created, but subsequent checks show VLAN 100 is not present in the running configuration. The switch's management interface is in VLAN 99 with IP 10.10.99.10/24, and the engineer's workstation is on a different subnet (10.10.88.0/24). The switch has the following relevant configuration: ip default-gateway 10.10.99.1, and a route for 10.10.88.0/24 via 10.10.99.1. The engineer also verified that the REST API credentials are correct and that the switch's HTTP server is enabled. Which action should the engineer take to resolve the issue?

Question 1hardmultiple choice

Open the full VLAN trunking answer →

A
Resend the PUT request with the VLAN configuration nested under 'Cisco-IOS-XE-native:native/vlan' in YANG format.
Why wrong: The request structure appears correct as a 201 was returned. Resending would not fix the missing commit.
B
Reboot the switch to force the candidate configuration to become active.
Why wrong: Rebooting is an extreme measure and would not commit candidate changes; it might even discard uncommitted configurations.
C
Send a commit operation to the RESTCONF API using the 'cisco-ia:commit' RPC to apply the candidate datastore changes.
On Cisco IOS-XE devices, configuration changes via RESTCONF are staged in the candidate datastore and must be explicitly committed. This is the likely missing step.
D
Check the MTU on the switch's management interface to ensure it can accept the configuration payload.
Why wrong: MTU issues would likely cause a failed or dropped request, not a successful 201 response with no configuration change.

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

✓

Send a commit operation to the RESTCONF API using the 'cisco-ia:commit' RPC to apply the candidate datastore changes.

The 201 Created response indicates the REST API request was accepted, but the VLAN is not appearing in the running config. This suggests the configuration was written to the candidate datastore but not committed. Cisco's RESTCONF requires a commit operation after editing the candidate datastore. To commit changes, a PATCH or POST request to the 'ietf-restconf:operations' with 'cisco-ia:commit' is needed. Alternatively, the switch might be using 'immediate' mode, but the default is 'candidate'. Checking the 'default-operation' setting would help, but the most direct correct action is to commit the changes. Distractors: checking MTU, resending the request with different data, or restarting the switch.

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.

✗
Resend the PUT request with the VLAN configuration nested under 'Cisco-IOS-XE-native:native/vlan' in YANG format.
Why it's wrong here
The request structure appears correct as a 201 was returned. Resending would not fix the missing commit.
✗
Reboot the switch to force the candidate configuration to become active.
Why it's wrong here
Rebooting is an extreme measure and would not commit candidate changes; it might even discard uncommitted configurations.
✓
Send a commit operation to the RESTCONF API using the 'cisco-ia:commit' RPC to apply the candidate datastore changes.
Why this is correct
On Cisco IOS-XE devices, configuration changes via RESTCONF are staged in the candidate datastore and must be explicitly committed. This is the likely missing step.
Related concept
Access ports place end devices into a single VLAN.
✗
Check the MTU on the switch's management interface to ensure it can accept the configuration payload.
Why it's wrong here
MTU issues would likely cause a failed or dropped request, not a successful 201 response with no configuration change.

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 200-901 questions on switching, trunking, and access-port configuration.

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FAQ

Questions learners often ask

What does this 200-901 question test?

Network Fundamentals — This question tests Network Fundamentals — Access ports place end devices into a single VLAN..

What is the correct answer to this question?

The correct answer is: Send a commit operation to the RESTCONF API using the 'cisco-ia:commit' RPC to apply the candidate datastore changes. — The 201 Created response indicates the REST API request was accepted, but the VLAN is not appearing in the running config. This suggests the configuration was written to the candidate datastore but not committed. Cisco's RESTCONF requires a commit operation after editing the candidate datastore. To commit changes, a PATCH or POST request to the 'ietf-restconf:operations' with 'cisco-ia:commit' is needed. Alternatively, the switch might be using 'immediate' mode, but the default is 'candidate'. Checking the 'default-operation' setting would help, but the most direct correct action is to commit the changes. Distractors: checking MTU, resending the request with different data, or restarting the switch.

What should I do if I get this 200-901 question wrong?

What is the key concept behind this question?

Access ports place end devices into a single VLAN.

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