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200-901 Practice Question: A company has a three-tier data center…
A company has a three-tier data center architecture with access, aggregation, and core layers. The network team is migrating to a leaf-spine architecture to support increasing east-west traffic. The current network uses STP for loop prevention, and the team wants to eliminate STP in the new design. They plan to use VXLAN overlays with BGP EVPN for control plane. During a pilot deployment, the team notices that some legacy servers that rely on traditional VLANs are not reachable across the new fabric. The servers are connected to access switches that are part of the leaf layer. The access switches are configured as VXLAN tunnel endpoints (VTEPs) but the legacy servers are still using traditional VLANs. The team needs to ensure connectivity between the legacy VLAN-based servers and the new VXLAN-based network. What is the best approach to integrate these legacy servers without changing their configuration?
⚠ Common exam trap
Many candidates confuse Layer 2 stretching (Option C) with a Layer 2 gateway, not realizing that stretching VLANs across the fabric would reintroduce STP dependencies and does not provide the necessary gateway function for legacy VLAN-based devices.
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
✓
Implement a Layer 2 gateway (L2GW) on the leaf switches to bridge VLANs to VXLAN using IRB
An Integrated Routing and Bridging (IRB) interface on the leaf switch acts as a Layer 2 gateway (L2GW), bridging the legacy VLAN to a VXLAN segment. This allows the legacy server, which still uses traditional VLAN tagging, to communicate with the VXLAN-based fabric without any configuration changes on the server. The IRB interface performs the VLAN-to-VXLAN mapping and handles ARP suppression, enabling seamless integration.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Create a separate VRF for legacy VLANs and redistribute into BGP EVPN
Why it's wrong here
This adds complexity and does not solve L2 connectivity.
- ✓
Implement a Layer 2 gateway (L2GW) on the leaf switches to bridge VLANs to VXLAN using IRB
Why this is correct
IRB provides seamless bridging between VLAN and VXLAN.
- ✗
Configure the same VLAN on all leaf switches and use VXLAN to stretch the VLAN across the fabric
Why it's wrong here
Stretching VLANs is not recommended for large fabrics.
- ✗
Reconfigure the legacy servers to use VXLAN encapsulation
Why it's wrong here
Server configuration change is to be avoided.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 200-901 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 200-901 exam.