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Refer to the exhibit.
An application called App_1 is hosted on the server called S1. A silent host application. App_2. is hosted on S2. Both applications use the same VLAN encapsulation, which action forces Cisco ACI fabric to learn App_2 on ACI leaf 2?
The scenario involves an application (App_1) on server S1 and a silent host application (App_2) on S2, both using the same VLAN encapsulation. The task is to force the ACI fabric to learn App_2 on Leaf-2. A silent host does not generate traffic, so special handling is needed.
Requirement Analysis
A silent host requires flooding (e.g., ARP or unknown unicast) to be learned by the fabric when it moves or is detected.
The goal is to ensure Leaf-2 learns App_2's endpoint.
Option Evaluation
A . Set Multi-Destination Flooding to Drop:
Dropping multi-destination traffic prevents learning, which is counterproductive for a silent host.
B . Set Unicast Routing to Hardware Proxy:
Hardware proxy optimizes unicast routing but does not force learning of a silent host via flooding.
C . Set L2 Unknown Unicast to Flood:
Enabling L2 unknown unicast flooding causes the fabric to flood traffic (e.g., ARP) across the bridge domain, allowing Leaf-2 to learn App_2's MAC address even if it is silent.
D . Set L3 Unknown Multicast to Optimized Flood:
This applies to multicast traffic and is irrelevant for learning a silent host's MAC address.
Final Answer Justification
C is correct because flooding L2 unknown unicast traffic ensures the ACI fabric learns App_2 on Leaf-2 by propagating ARP or other discovery traffic.
Primary Cisco Reference:
Cisco ACI Endpoint Learning Guide, 'Flooding for Silent Hosts.'
Cisco APIC Bridge Domain Configuration Guide.