Cisco Updated 300-630 Exam Questions and Answers by elyas

The minimum MTU value that must be supported by the ISN to allow control plane endpoint information exchange between sites in a Cisco ACI Multi-Site setup with default settings is 1554 bytes (B). This accounts for the standard MTU of 1500 bytes plus additional overhead for VXLAN encapsulation. An MTU of 9000 (A) or 9100 © is not the minimum required, and 1600 (D) is not related to the default fabric settings5. References := (Multi-site / Multi-Pod MTU Jumbo Frames5)

When traffic to certain endpoints is dropped in a Cisco ACI fabric configured with hardware proxy, setting the L2 Unknown Unicast option to Flood for Layer 2 switched traffic can prevent this problem. This mode allows unknown unicast traffic to be flooded within the bridge domain, rather than being sent to the spine proxy and potentially discarded if the destination is unknown5.

References := Solved: Unknown Unicast in ACI Fabric - Cisco Community

In a Cisco ACI Multi-Site fabric, when the Inter-Site BUM Traffic Allow option is enabled in a specific stretched bridge domain, ingress replication on the spines in the source site is used to forward Broadcast, Unknown unicast, and Multicast (BUM) traffic to all endpoints in the same broadcast domain. This method ensures that BUM traffic is efficiently replicated across the fabric, reaching all relevant endpoints without overwhelming the network with unnecessary traffic4.

References := Solved: Cisco ACI Multipod - BUM traffic - Cisco Community.

 When Leaf 1002 receives a packet from a host attached to Leaf 1001, it learns the MAC address of the source from Leaf 1001. Additionally, Leaf 1002 learns the IP address of the source.

References := Cisco APIC Layer 2 Networking Configuration Guide, Release 5.2(x)