Which routes does the overlay management protocol advertise in an SD-WAN overlay?

Underlay and MPLS are transport technologies, not specific route types advertised by OMP itself.

Primary, backup, and load-balanced describe traffic engineering states, not the fundamental types of routes OMP advertises.

OMP advertises prefix routes (network reachability information), TLOC routes (transport location information binding a system IP to a transport), and service routes (information about network services behind a device) to build the overlay topology. These three route types are fundamental for centralized control plane functionality in Cisco SD-WAN.

Internet and MPLS are transport types, and backup refers to a traffic state, none are specific OMP route types.