- A
Define a custom flow record that includes the 'match ipv4 vlan' or 'match ipv4 vrf' field to identify each customer's traffic, and apply a single flow monitor on the shared interface.
Correct because including the VRF or VLAN match field in the flow record allows the collector to distinguish flows per customer.
- B
Configure a separate flow monitor for each customer interface and export to different collectors.
Why wrong: Incorrect because if customers share an interface (e.g., MPLS VPN), separate monitors won't separate flows; also, multiple collectors add complexity.
- C
Use NetFlow v9 export with the 'match ipv4 source address' field only, and rely on the collector to separate by source IP.
Why wrong: Incorrect because source IP alone may not uniquely identify customers if they use overlapping private IPs.
- D
Enable SNMP interface polling to track per-customer traffic statistics.
Why wrong: Incorrect because SNMP provides aggregate interface counters, not per-flow or per-customer granularity.
Quick Answer
The correct approach is to define a custom flow record that includes the 'match ipv4 vlan' or 'match ipv4 vrf' field to identify each customer's traffic, and apply a single flow monitor on the shared interface. This works because Flexible NetFlow allows you to customize flow records with key fields like VRF or VLAN, which act as unique tags to separate flows per customer even when multiple customers share the same physical interface. On the ENCOR 350-401 exam, this question tests your understanding of Flexible NetFlow’s ability to export per-customer data without needing separate monitors or export destinations—a common trap is assuming you must create multiple flow monitors per interface, which would still mix flows if customers share a link. Remember, the key is to match on the VRF or VLAN field within a single flow record, not to multiply monitors. Memory tip: “One monitor, match the VRF—keep customers separate without grief.”
350-401 NetFlow and Telemetry Practice Question
This 350-401 practice question tests your understanding of netflow and telemetry. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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 service provider is using Cisco ASR 9000 routers and needs to collect NetFlow data from multiple customers' traffic. The engineer wants to ensure that flow records from different customers are not mixed and can be identified separately. The router supports Flexible NetFlow. What is the best approach?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"best"Why it matters: Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
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
Define a custom flow record that includes the 'match ipv4 vlan' or 'match ipv4 vrf' field to identify each customer's traffic, and apply a single flow monitor on the shared interface.
Flexible NetFlow allows customization of flow records. Option A is correct by using a flow record with a 'match ipv4 vlan' or 'match ipv4 vrf' field to tag flows per customer. Option B is incorrect because separate flow monitors for each interface would still mix flows if multiple customers share an interface. Option C is incorrect because NetFlow v9 export format does not inherently separate customers. Option D is incorrect because SNMP is not suitable for per-customer flow identification.
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.
- ✓
Define a custom flow record that includes the 'match ipv4 vlan' or 'match ipv4 vrf' field to identify each customer's traffic, and apply a single flow monitor on the shared interface.
- ✗
Configure a separate flow monitor for each customer interface and export to different collectors.
Why it's wrong here
Incorrect because if customers share an interface (e.g., MPLS VPN), separate monitors won't separate flows; also, multiple collectors add complexity.
- ✗
Use NetFlow v9 export with the 'match ipv4 source address' field only, and rely on the collector to separate by source IP.
Why it's wrong here
Incorrect because source IP alone may not uniquely identify customers if they use overlapping private IPs.
- ✗
Enable SNMP interface polling to track per-customer traffic statistics.
Why it's wrong here
Incorrect because SNMP provides aggregate interface counters, not per-flow or per-customer granularity.
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.
- →
NetFlow and Telemetry — study guide chapter
Learn the concepts, then practise the questions
- →
NetFlow and Telemetry practice questions
Targeted practice on this topic area only
- →
All 350-401 questions
2,015 questions across all exam domains
- →
ENCOR 350-401 study guide
Full concept coverage aligned to exam objectives
- →
350-401 practice test guide
How to use practice tests most effectively before exam day
Related practice questions
Related 350-401 practice-question pages
Use these pages to review the topic behind this question. This is how one missed question becomes focused revision.
Architecture practice questions
Practise 350-401 questions linked to Architecture.
Enterprise Network Design practice questions
Practise 350-401 questions linked to Enterprise Network Design.
SD-Access Architecture practice questions
Practise 350-401 questions linked to SD-Access Architecture.
SD-WAN Architecture practice questions
Practise 350-401 questions linked to SD-WAN Architecture.
QoS Architecture practice questions
Practise 350-401 questions linked to QoS Architecture.
Virtualization practice questions
Practise 350-401 questions linked to Virtualization.
Network Function Virtualization practice questions
Practise 350-401 questions linked to Network Function Virtualization.
Virtual Machines and Hypervisors practice questions
Practise 350-401 questions linked to Virtual Machines and Hypervisors.
VRF and Path Isolation practice questions
Practise 350-401 questions linked to VRF and Path Isolation.
Infrastructure practice questions
Practise 350-401 questions linked to Infrastructure.
OSPF practice questions
Practise 350-401 questions linked to OSPF.
BGP practice questions
Practise 350-401 questions linked to BGP.
Practice this exam
Start a free 350-401 practice session
Short sessions build daily habit. Longer sessions build exam-day stamina. Try a timed session to simulate real conditions.
FAQ
Questions learners often ask
What does this 350-401 question test?
NetFlow and Telemetry — This question tests NetFlow and Telemetry — Access ports place end devices into a single VLAN..
What is the correct answer to this question?
The correct answer is: Define a custom flow record that includes the 'match ipv4 vlan' or 'match ipv4 vrf' field to identify each customer's traffic, and apply a single flow monitor on the shared interface. — Flexible NetFlow allows customization of flow records. Option A is correct by using a flow record with a 'match ipv4 vlan' or 'match ipv4 vrf' field to tag flows per customer. Option B is incorrect because separate flow monitors for each interface would still mix flows if multiple customers share an interface. Option C is incorrect because NetFlow v9 export format does not inherently separate customers. Option D is incorrect because SNMP is not suitable for per-customer flow identification.
What should I do if I get this 350-401 question wrong?
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.
Are there clue words in this question I should notice?
Yes — watch for: "best". Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
What is the key concept behind this question?
Access ports place end devices into a single VLAN.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Last reviewed: Jun 18, 2026
This 350-401 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 350-401 exam.
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.