300-420 · Question #253
An engineer is designing a BGP solution supporting a VXLAN environment over a Layer 3 IPv4 network fabric with these requirements: - provide Layer 2 adjacency - allow VM migration of workloads…
The correct answer is B. L2VPN EVPN. BGP L2VPN EVPN is the address family that provides the MAC and IP reachability control plane for VXLAN, enabling Layer 2 adjacency and live VM migration across Layer 3 boundaries.
Question
An engineer is designing a BGP solution supporting a VXLAN environment over a Layer 3 IPv4 network fabric with these requirements:
- provide Layer 2 adjacency
- allow VM migration of workloads between sites
- IGP is OSPF
Which BGP address family must the engineer choose?
Options
- AL2VPN VPLS-VPWS
- BL2VPN EVPN
- CIPv4 unicast
- DVPNv4
How the community answered
(33 responses)- A6% (2)
- B76% (25)
- C3% (1)
- D15% (5)
Why each option
BGP L2VPN EVPN is the address family that provides the MAC and IP reachability control plane for VXLAN, enabling Layer 2 adjacency and live VM migration across Layer 3 boundaries.
L2VPN VPLS and VPWS are MPLS-based Layer 2 VPN technologies that do not support VXLAN encapsulation and lack native VM mobility signaling.
L2VPN EVPN (RFC 7432) distributes MAC and IP binding information between VTEP peers using BGP, extending Layer 2 segments across a Layer 3 OSPF underlay. It natively supports VM mobility through the MAC Mobility extended community, which signals a MAC address move so remote VTEPs update their forwarding tables and maintain seamless Layer 2 adjacency during workload migration between sites.
IPv4 unicast BGP only carries Layer 3 IP prefix reachability and cannot distribute MAC addresses or provide the Layer 2 adjacency required for VM migration.
VPNv4 is the BGP address family for MPLS Layer 3 VPNs (RFC 4364) and provides per-VRF IP routing isolation, not Layer 2 bridging or MAC reachability for VXLAN environments.
Concept tested: BGP L2VPN EVPN address family for VXLAN control plane
Source: https://www.cisco.com/c/en/us/td/docs/switches/datacenter/nexus9000/sw/9-x/vxlan/configuration/guide/b_Cisco_Nexus_9000_Series_NX-OS_VXLAN_Configuration_Guide_9x.html
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