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300-410 Practice Question: Configures Flexible NetFlow on a router to…
A network engineer configures Flexible NetFlow on a router to monitor traffic on a trunk interface with multiple VLANs. The flow monitor is applied to the physical interface. The engineer notices that all flows show the same VLAN ID in the collector, even though traffic from different VLANs is present. What is the most likely cause?
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 flow record does not include any VLAN match fields.
To capture VLAN information in Flexible NetFlow, the flow record must include 'match dot1q vlan' or 'match vlan' fields. Without these, the VLAN ID is not recorded, and the collector may show a default or incorrect value.
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 flow record does not include any VLAN match fields.
Why this is correct
Without 'match dot1q vlan' in the flow record, VLAN information is not captured, so all flows appear with the same (or zero) VLAN ID.
- ✗
The trunk interface is not configured with 'switchport trunk encapsulation dot1q'.
Why it's wrong here
This is a Layer 2 switch configuration; on a router, subinterfaces are used for VLAN tagging.
- ✗
The flow monitor is applied only to the physical interface, not the subinterfaces.
Why it's wrong here
Applying the monitor to the physical interface should capture all VLAN traffic; the issue is the record definition.
- ✗
The collector does not support VLAN fields.
Why it's wrong here
Even if the collector does not display VLAN, the router would still export it if configured.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 300-410 practice question is part of Courseiva's free Cisco certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 300-410 exam.