Which component of the Cisco SD-WAN architecture oversees the control plane of overlay network to establish, adjust, and maintain the connections that form the Cisco SD-WAN fabric?

APIC-EM is Cisco's legacy Application Policy Infrastructure Controller for Enterprise Module used in older SDN deployments and is not a component of the Cisco SD-WAN architecture.

vSmart acts as the central control plane brain of the Cisco SD-WAN architecture by running the Overlay Management Protocol (OMP) and maintaining OMP sessions with all WAN Edge routers. It computes and distributes route information, security policies, and service chaining instructions, dynamically adjusting the SD-WAN fabric topology as network conditions change.

vManage is the management plane component that provides the GUI and API for configuration and monitoring, but it does not handle the control plane OMP sessions or routing distribution.

vBond serves as the orchestration plane, facilitating initial authentication and NAT traversal for new devices, but it does not maintain ongoing control plane sessions or distribute routing information.