Quick Answer
The answer is VXLAN with EVPN control plane, because this combination creates a scalable Layer 2 overlay that extends VLANs across the entire leaf-spine fabric, allowing virtual machines to move between racks without requiring any IP address changes. EVPN uses BGP to distribute MAC and IP reachability information among leaf switches, so each leaf dynamically learns where a VM resides and can forward traffic accordingly, regardless of the VM’s physical location. On the ENCOR 350-401 exam, this question tests your understanding of overlay technologies for data center mobility; a common trap is choosing traditional VLAN trunking or STP, which cannot span a leaf-spine architecture without breaking. Remember the key: EVPN is the control plane that makes VXLAN intelligent—think “EVPN learns, VXLAN carries.”
This 350-401 practice question tests your understanding of virtualization. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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 organization is migrating from a traditional three-tier architecture to a leaf-spine fabric using VXLAN EVPN. The design requires that virtual machines can move between racks without IP address changes. Which technology must be enabled at the leaf switches to support this mobility?
Overlay Transport Virtualization (OTV).
Why wrong: OTV is for data center interconnect, not internal fabric mobility.
VXLAN with EVPN control plane.
Provides Layer 2 overlay over Layer 3 underlay, enabling VM mobility.
VRF-Lite with route redistribution.
Why wrong: VRF-Lite does not extend Layer 2 across IP networks.
MPLS L3VPN with BGP.
Why wrong: MPLS L3VPN is a Layer 3 VPN, does not support Layer 2 mobility.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
VXLAN with EVPN control plane.
VXLAN with EVPN control plane (B) is correct because it provides a Layer 2 overlay network that extends VLANs across the leaf-spine fabric, enabling virtual machine mobility without IP address changes. EVPN uses BGP to distribute MAC and IP address information, allowing the leaf switches to learn and forward traffic to VMs regardless of their physical location, which is essential for seamless VM migration between racks.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
Overlay Transport Virtualization (OTV).
Why it's wrong here
OTV is for data center interconnect, not internal fabric mobility.
VXLAN with EVPN control plane.
Why this is correct
Provides Layer 2 overlay over Layer 3 underlay, enabling VM mobility.
Related concept
Read the scenario before looking for a memorised answer.
VRF-Lite with route redistribution.
Why it's wrong here
VRF-Lite does not extend Layer 2 across IP networks.
MPLS L3VPN with BGP.
Why it's wrong here
MPLS L3VPN is a Layer 3 VPN, does not support Layer 2 mobility.
Common exam traps
Cisco often tests the distinction between Layer 2 extension technologies (VXLAN EVPN) and Layer 3 VPNs (MPLS L3VPN), leading candidates to mistakenly choose MPLS L3VPN because it also uses BGP, but it cannot support Layer 2 mobility without IP changes.
Detailed technical explanation
VXLAN EVPN uses BGP EVPN (RFC 7432) to advertise MAC/IP address bindings via Type 2 routes, and the control plane handles MAC mobility by updating the sequence number in the route, allowing leaf switches to redirect traffic to the new VM location. In a real-world scenario, when a VM moves, the leaf switch sends a BGP update with a higher sequence number, and other leaf switches update their forwarding tables, ensuring minimal traffic disruption without requiring ARP flooding or STP convergence.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
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
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FAQ
Virtualization — This question tests Virtualization — Read the scenario before looking for a memorised answer..
The correct answer is: VXLAN with EVPN control plane. — VXLAN with EVPN control plane (B) is correct because it provides a Layer 2 overlay network that extends VLANs across the leaf-spine fabric, enabling virtual machine mobility without IP address changes. EVPN uses BGP to distribute MAC and IP address information, allowing the leaf switches to learn and forward traffic to VMs regardless of their physical location, which is essential for seamless VM migration between racks.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 11, 2026
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