The correct actions are to ensure VNI 10100 is added under the NVE interface and to verify consistent VLAN-to-VNI mapping across all VTEPs. This is because VXLAN EVPN relies on the NVE interface to enable tunnel termination for each VNI; without explicit inclusion under the NVE, the VTEP cannot encapsulate or decapsulate traffic for that segment. Additionally, if VLAN 100 maps to VNI 10100 on one switch but not on another, the fabric lacks a consistent overlay-to-underlay binding, causing unreachability even when other VLANs function. On the ENCOR 350-401 exam, this tests your understanding of VXLAN control-plane integration with EVPN, often appearing as a troubleshooting scenario where a single VNI fails while others work—a classic trap is assuming the NVE interface being up means all VNIs are active. Remember the memory tip: “No VNI under NVE, no VXLAN for you.”
CCNP Virtualization Practice Question
This 350-401 practice question tests your understanding of virtualization. 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 data center uses Cisco Nexus 9000 switches with VXLAN EVPN to provide network virtualization. The operations team notices that VLAN 100 (mapped to VNI 10100) is not reachable across the fabric, although other VLANs work fine. The NVE interface is up, and the EVPN address-family is configured. Which two actions should the engineer take to isolate the issue?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Verify that VLAN 100 is mapped to VNI 10100 consistently on all VTEPs.
Option C is correct because VXLAN EVPN requires consistent VLAN-to-VNI mapping across all VTEPs in the fabric. If VLAN 100 is mapped to VNI 10100 on some switches but not others, traffic for that VNI will not be forwarded correctly, as the mapping is used to associate local VLANs with the VXLAN segment. Option D is correct because the VNI must be explicitly enabled under the NVE interface to participate in VXLAN tunnel termination; without it, the VTEP will not encapsulate or decapsulate traffic for VNI 10100.
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.
✗
Check if EVPN type-3 routes are being advertised for VNI 10100.
Why it's wrong here
Type-3 routes are for multicast, not for unicast MAC/IP.
✗
Confirm that multicast group 239.1.1.1 is reachable across the underlay.
Common exam trap: answer the scenario, not the keyword
Cisco often tests the distinction between control-plane (BGP EVPN) and data-plane (multicast) VXLAN, leading candidates to incorrectly check multicast reachability (Option B) when the issue is a missing or inconsistent VNI configuration.
Detailed technical explanation
How to think about this question
In VXLAN EVPN, the NVE interface is the logical tunnel endpoint that terminates VXLAN tunnels, and each VNI must be explicitly added under the NVE interface using the 'member vni' command to enable encapsulation/decapsulation. The VLAN-to-VNI mapping is configured under the VLAN interface or via 'vlan configuration' commands, and inconsistency across VTEPs can cause asymmetric routing or black-holing of traffic for that specific VNI. A common real-world scenario is when a new VLAN is added to only one leaf switch, causing traffic to fail for that segment while others work fine.
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.
Virtualization — This question tests Virtualization — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Verify that VLAN 100 is mapped to VNI 10100 consistently on all VTEPs. — Option C is correct because VXLAN EVPN requires consistent VLAN-to-VNI mapping across all VTEPs in the fabric. If VLAN 100 is mapped to VNI 10100 on some switches but not others, traffic for that VNI will not be forwarded correctly, as the mapping is used to associate local VLANs with the VXLAN segment. Option D is correct because the VNI must be explicitly enabled under the NVE interface to participate in VXLAN tunnel termination; without it, the VTEP will not encapsulate or decapsulate traffic for VNI 10100.
What should I do if I get this 350-401 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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