You are deploying a three-stage EVPN environment with VXLAN using EX and QFX Series switches.

In a three-stage EVPN-VXLAN fabric (Spine-Leaf architecture) where leaf devices perform the gateway services (Edge-Routed Bridging or ERB):

VTEP Functionality (Option B): Leaf devices act as VXLAN Tunnel End Points (VTEPs). They are responsible for encapsulating Ethernet frames from locally connected hosts into VXLAN packets for transport across the IP fabric and de-encapsulating incoming VXLAN packets.

Fabric Support (Option C): In a standard Juniper IP fabric design, both the leaf and spine devices are typically expected to support VXLAN and EVPN capabilities. While spines in an ERB design might only perform IP forwarding in the underlay, they often participate in the BGP control plane (as Route Reflectors) or provide the ability to transition to Centrally-Routed Bridging (CRB) where spines would act as gateways.

Incorrect Options: Option A is incorrect because the entire fabric infrastructure must be " VXLAN aware " in terms of MTU settings and routing capability to support the overlay. Option D is incorrect because in an ERB design, the spine devices are high-speed transit nodes and do not terminate VXLAN tunnels; only the edge (leaf) devices act as VTEPs.