The question asks for the command set to configure VXLAN and MP-BGP EVPN on a Cisco Nexus 9000 Series platform, with OSPF as the underlay and a distributed default gateway on a VLAN interface. After evaluating the options and considering the discussion, the AI suggests answer A.

The suggested answer is A.

Reasoning:
Option A includes the following commands:

feature nv overlay: Enables the Network Virtualization Overlay feature, which is essential for VXLAN.
feature vn-segment-vlan-based: Enables VLAN-based VN-Segments, necessary for VXLAN configuration.
feature bgp: Enables the Border Gateway Protocol (BGP), which is used for MP-BGP EVPN control plane.
nv overlay-evpn: Enables the NV Overlay EVPN feature.
feature ospf: Enables the Open Shortest Path First (OSPF) routing protocol for the underlay network.
feature interface-vlan: Enables VLAN interfaces, which are needed for the distributed default gateway.

These commands collectively address all the requirements specified in the question, including VXLAN, MP-BGP EVPN, OSPF underlay, and distributed default gateway on a VLAN interface.
The Cisco documentation confirms that these features are required for VXLAN and MP-BGP EVPN configuration on Nexus 9000 series switches.

Reasons for not choosing the other answers:

Option B: Includes feature bfd and feature ngmvpn, which are not explicitly required for the basic VXLAN and MP-BGP EVPN setup described in the question. While BFD (Bidirectional Forwarding Detection) can be useful for faster failure detection, it is not a mandatory initial configuration requirement. NGmvpn is for multicast, which is not specified in the question.
Option C: Includes feature bfd and feature fabric forwarding and feature ospfv3, which are not explicitly required for the basic VXLAN and MP-BGP EVPN setup described in the question. Fabric forwarding is related to ACI, which is not stated in the question. OSPFv3 is for IPv6, while OSPF is sufficient if the underlay is running IPv4.
Option D: Includes feature bfd and feature ngmvpn, which are not explicitly required for the basic VXLAN and MP-BGP EVPN setup described in the question.

While some of the other options contain commands that could be used in a VXLAN/EVPN environment, option A provides the minimal and necessary set of commands to meet the requirements outlined in the question.

It's also important to note that while PIM (Protocol Independent Multicast) might be used in some VXLAN deployments, it's not explicitly stated as a requirement in the question. The question focuses on the initial configuration with OSPF as the underlay.

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