In the Cisco ACI fabric, to ensure that the IP address of Server S1 is learned and the IP addresses of BC1 and BC2 are not learned, one must limit IP learning to a specific subnet and suppress ARP responses from BC1 and BC2. By checking the "Limit IP learning to subnet" box (Option A), it ensures that only IPs within a defined subnet are learned, which would include Server S1's IP but exclude BC1 and BC2 if they are outside of this subnet.Suppressing ARP response on BC1 and BC2 (Option D) prevents these devices from responding to ARP requests, which in turn prevents their IPs from being learned by other devices in the network. References := ( Implementing Cisco Application Centric Infrastructure Official Cert Guide )