Which device replicates Broadcast.

 In a Cisco ACI Multi-Site setup, the source leaf is responsible for flooding BUM (Broadcast, Unicast, and Multicast) traffic to the specific multicast group or GIPo (Group IP Overlay). This process involves the ingress replication function on the spine nodes of the source site to replicate BUM traffic to all remote sites where the bridge domain is stretched12.

References := Cisco ACI Multi-Site Architecture White Paper, ACI Multi-Site Data Plane Communication - DCLessons