Bridge Domain Configuration for Layer 2 Unknown Unicast Traffic

A.

In Cisco Application Centric Infrastructure (ACI), a bridge domain is a construct that connects endpoints in the same Layer 2 domain. The hardware-proxy option is a feature that enables Layer 2 unknown unicast traffic to be forwarded to the spine switch for hardware-based forwarding instead of being sent to the controller for software-based forwarding.

Based on the given options, the correct answer to the question is C - "The leaf switch forwards the Layers 2 unknown unicast packets to all other leaf switches if it is unable to find the MAC address in its local forwarding tables."

Explanation for each option:

A. The leaf switch drops the Layer 2 unknown unicast packet if it is unable to find the MAC address in the local forwarding tables. This statement is not true because the hardware-proxy option forwards the Layer 2 unknown unicast traffic to the spine switch for forwarding, not to the local forwarding tables of the leaf switch.

B. The Layer 2 unknown hardware proxy lacks support of the topology change notification. This statement is not related to the configuration of a bridge domain with the hardware-proxy option and is therefore not a correct answer to the question.

C. The leaf switch forwards the Layers 2 unknown unicast packets to all other leaf switches if it is unable to find the MAC address in its local forwarding tables. This statement is true. When the hardware-proxy option is enabled, if a leaf switch receives a Layer 2 unknown unicast packet and does not have the destination MAC address in its local forwarding tables, it floods the packet to all other leaf switches in the same bridge domain. The other leaf switches will then forward the packet to their local endpoints if the destination MAC address is found in their local forwarding tables. This flooding mechanism ensures that the packet reaches its destination and enables hardware-based forwarding for performance and scalability.

D. The spine switch drops the Layer 2 unknown unicast packet if it is unable to find the MAC address in the proxy database. This statement is not true. The spine switch does not drop Layer 2 unknown unicast packets but instead forwards them to the appropriate destination based on the proxy database, which is used for hardware-based forwarding.