Migrating to VXLAN EVPN with VRRP Gateway
A customer migrates from a traditional Layer 2 data center network into a new SDN-based, spine-and-leaf VXLAN EVPN data center within the same location. The networks are joined to enable host migration at Layer 2. What is the final migration step, after hosts have physically migrated, to have traffic flowing through the new network without changing any host configuration?
Community Votes
71% of anonymous learners picked answer B. Votes are pick records left by other test-takers — they are not the verified answer.
Community Insight
The exam tests knowledge of Cisco's official limitation regarding VRRP/HSRP in VXLAN EVPN migrations, specifically that the virtual MAC address cannot be shared across the legacy and new fabrics without disruption.
This question addresses the specific constraints of migrating from a traditional Layer 2 data center to an SDN-based spine-and-leaf VXLAN EVPN fabric when using VRRP. It establishes that non-disruptive migration is impossible in this scenario due to FHRP limitations.
Many candidates choose Option D because it attempts to maintain the same IP gateway (VRRP address), but they fail to realize that the associated MAC address changes between the legacy and VXLAN gateways, causing ARP resolution failures for endpoints.
Community Discussion (5 comments)
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Expert Analysis
Why the Answer Is Correct
The correct answer is B because Cisco documentation explicitly states that non-disruptive migration is not supported if the existing Classic LAN fabric uses VRRP or HSRP as the First Hop Redundancy Protocol (FHRP). Since the legacy network relies on VRRP, you cannot seamlessly hand off the gateway state to the new VXLAN EVPN fabric without breaking connectivity for endpoints that have cached the old VRRP MAC address. Therefore, a maintenance window is required to shut down the legacy SVIs and activate the new ones.Why the Other Options Are Wrong
Option A is incorrect because simply increasing priority does not solve the underlying issue of different virtual MAC addresses being used by the legacy vs. VXLAN gateways; hosts will still send traffic to the wrong MAC. Option C is too vague and doesn't address the Layer 3 gateway configuration. Option D suggests clearing ARP caches, which is impractical for a large-scale customer migration and contradicts the goal of minimal host configuration changes; furthermore, even with cleared caches, the transition involves a period where the gateway moves, which constitutes a disruption requiring a scheduled window.Community Comment Notes
Community feedback strongly supports the necessity of a maintenance window. As one user noted, "Non-disruptive migration is not supported if the existing Classic LAN fabric is using VRRP... In this case, you must schedule a maintenance window." Another commenter highlighted that changing the FHRP virtual MAC results in the highest probability of endpoint issues, confirming why a clean break (shutting down legacy) is the standard procedure.Official Reference
Exam Strategy
Always check for specific protocol limitations in migration scenarios. If the question mentions VRRP or HSRP in a VXLAN migration context, assume that a disruptive maintenance window is required unless the question specifies a specific technology like BGP EVPN route leaking that might allow otherwise (though VRRP itself is the blocker here).
Frequently Asked Questions
Why can't we just clear ARP caches on hosts?
Clearing ARP caches is not scalable or practical for a large customer environment. More importantly, the transition involves moving the active gateway, which inherently causes a brief outage regardless of cache state.
Does VXLAN EVPN support seamless VRRP handoff?
No. Cisco explicitly states that non-disruptive migration is not supported when VRRP or HSRP are used as the FHRP protocol due to virtual MAC address differences.