The correct answer is to configure "evpn" and "vni 10100 l2" under the BGP address-family l2vpn evpn. This is required because on a Nexus 9000, the BGP EVPN address-family must explicitly include the 'evpn' keyword to activate the EVPN control plane, and the 'vni 10100 l2' command tells BGP to advertise the Layer 2 VNI’s MAC and VTEP information as EVPN routes. Without these statements, BGP has no awareness of the VNI and will not generate any type-2 or type-3 routes for it, resulting in missing VNI routes. On the ENCOR 350-401 exam, this tests your understanding of the VXLAN EVPN BGP configuration hierarchy, where a common trap is assuming that simply enabling the l2vpn evpn address-family is enough—you must also explicitly associate each VNI. A helpful memory tip is: "EVPN needs two keys—the 'evpn' keyword and the 'vni l2' command—to unlock route advertisement."
350-401 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.
An engineer configures VXLAN EVPN on a Nexus 9000 switch. The configuration is shown. The switch does not advertise any EVPN routes for VNI 10100. Which configuration change is required to fix this issue?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Configure "evpn" and "vni 10100 l2" under the BGP address-family l2vpn evpn.
Option A is correct because for VXLAN EVPN on a Nexus 9000, the BGP address-family l2vpn evpn must explicitly contain the 'evpn' keyword and the 'vni 10100 l2' command to advertise Layer 2 VNI routes. Without this configuration, BGP does not know to inject the VNI's MAC/VTEP information into the EVPN route table, so no EVPN routes are advertised 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.
✓
Configure "evpn" and "vni 10100 l2" under the BGP address-family l2vpn evpn.
Why this is correct
The VNI must be activated under evpn for route advertisement.
Related concept
Read the scenario before looking for a memorised answer.
✗
Remove the mcast-group from the NVE member, because EVPN uses BGP for control plane.
Why it's wrong here
mcast-group is for data plane, but EVPN still needs the VNI enabled under evpn.
✗
Change the source-interface to a physical interface.
Why it's wrong here
Loopback is recommended for stability.
✗
Add an IP address to the VLAN 100 interface in the default VRF.
Common exam trap: answer the scenario, not the keyword
Cisco often tests the distinction between the NVE interface configuration (which enables VXLAN encapsulation) and the BGP EVPN address-family configuration (which enables route advertisement), leading candidates to mistakenly focus on NVE or interface settings instead of the missing BGP VNI injection.
Detailed technical explanation
How to think about this question
Under the hood, the 'vni 10100 l2' command under 'router bgp' > 'address-family l2vpn evpn' triggers BGP to create an EVPN route type 2 (MAC/IP advertisement) and type 3 (Inclusive Multicast Ethernet Tag) for that VNI. Without this explicit mapping, BGP ignores the VNI even if it is configured under the NVE interface. In real-world deployments, forgetting this step is a common misconfiguration that leads to silent blackholing of EVPN routes.
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.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this 350-401 question in full detail.
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: Configure "evpn" and "vni 10100 l2" under the BGP address-family l2vpn evpn. — Option A is correct because for VXLAN EVPN on a Nexus 9000, the BGP address-family l2vpn evpn must explicitly contain the 'evpn' keyword and the 'vni 10100 l2' command to advertise Layer 2 VNI routes. Without this configuration, BGP does not know to inject the VNI's MAC/VTEP information into the EVPN route table, so no EVPN routes are advertised 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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