A Cisco ACI leaf switch learns the source IP address of a packet that enters the front panel port of the switch. Which bridge domain setting is used?

ARP Flooding primarily concerns Layer 2 address resolution (MAC addresses) and broadcast behavior, not the learning of source IP addresses for unicast forwarding.

L3 Unknown Multicast Flooding defines how unknown multicast IP traffic is handled, which is distinct from learning a source IP address for unicast communication.

L2 Unknown Unicast - Hardware proxy dictates how unknown Layer 2 unicast traffic is handled within the fabric (e.g., sending to the spine proxy), but it does not directly govern source IP address learning.

When 'Unicast Routing' is enabled on a Bridge Domain (BD) in Cisco ACI, the leaf switch is configured to perform Layer 3 functions, including learning the source IP addresses of hosts connected to that BD. This setting allows the BD to act as an IP subnet boundary and enables the switch to route traffic based on IP addresses.