What is a requirement for a WAN Edge to reach vManage, vBond, and vSmart controllers in a data center?

OMP (Overlay Management Protocol) is used for exchanging routing and policy information *within* the SD-WAN overlay, not for establishing underlying IP reachability to the controllers themselves.

An Interior Gateway Protocol (IGP) like OSPF or EIGRP running in the underlying transport network is required to provide IP reachability for the WAN Edge device to discover and connect to the vManage, vBond, and vSmart controllers in the data center.

QoS (Quality of Service) is used for traffic prioritization and management, not for establishing the fundamental IP reachability between network devices and controllers.

TLS (Transport Layer Security) is used to secure the control plane connections *after* IP reachability is established, but it does not provide the underlying network reachability itself.