Which protocol is used in the Cisco ACI fabric for automatic discovery?

LLDP is a standard Layer 2 protocol that Cisco ACI leaf and spine switches use to automatically discover the physical topology and capabilities of directly connected devices. This discovery is fundamental for the fabric's initial bring-up, inventory, and ongoing operational awareness without manual intervention.

IS-IS is a link-state routing protocol used for path determination in IP networks, not for automatic device discovery in ACI.

CFS (Cisco Fabric Services) is a proprietary protocol used in Cisco SAN environments for configuration and state distribution, not for ACI device discovery.

COOP (Council of Oracles Protocol) is an ACI internal control plane protocol responsible for synchronizing the endpoint database across the fabric, not for physical device discovery.