400-007 · Question #264
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 migratio
The correct answer is C. The migrated VLAN should be pruned from the Layer 2 interconnects. After migrating a VLAN into the VXLAN EVPN fabric, that VLAN must be pruned from the Layer 2 interconnect trunks to prevent bridging loops and ensure all traffic transits the EVPN control plane.
Question
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. Which activity should be completed each time a legacy network is migrated?
Options
- AThe migrated network should be added to the EVPN BGP routing
- BThe migrated network should have a VXLAN VNID configured within the new network
- CThe migrated VLAN should be pruned from the Layer 2 interconnects
- DThe migrated network should be advertised to the EVPN network as a Type 2 network
How the community answered
(64 responses)- A8% (5)
- B3% (2)
- C70% (45)
- D19% (12)
Why each option
After migrating a VLAN into the VXLAN EVPN fabric, that VLAN must be pruned from the Layer 2 interconnect trunks to prevent bridging loops and ensure all traffic transits the EVPN control plane.
Adding networks to EVPN BGP routing is part of the initial fabric provisioning, not a per-migration step performed each time a legacy VLAN is cut over.
VXLAN VNIDs are pre-configured in the fabric before migration begins and map to the VLANs that will be migrated; they are not configured on a per-migration-event basis.
During a phased migration, a Layer 2 interconnect (often called a hand-off or DCI link) bridges the legacy network and the new EVPN fabric to allow host mobility. Once a specific VLAN's hosts have been fully migrated, leaving that VLAN active on the interconnect creates a loop risk and causes traffic to bypass the EVPN fabric. Pruning the VLAN from the interconnect forces all traffic for that subnet to traverse the VXLAN EVPN path, completing the migration cleanly.
EVPN Type 2 routes carry individual MAC and IP address advertisements learned from hosts, not network-level prefix advertisements, so advertising a migrated network as Type 2 is technically incorrect.
Concept tested: VXLAN EVPN phased Layer 2 migration pruning
Source: https://www.cisco.com/c/en/us/td/docs/switches/datacenter/nexus9000/sw/93x/vxlan/configuration/guide/b-cisco-nexus-9000-series-nxos-vxlan-configuration-guide-93x/b-cisco-nexus-9000-series-nxos-vxlan-configuration-guide-93x_chapter_010.html
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