How is internet access provided to a WAN edge router that is connected to a MPLS transport link?

OMP advertises routes, but TLOC extensions are the specific mechanism for signaling direct internet connectivity from a WAN Edge to the SD-WAN fabric, which is distinct from merely advertising a default route.

This describes how a WAN Edge obtains internet access (e.g., via 4G/5G or local DIA) but not how it provides or routes internet access to other routers in the SD-WAN overlay.

An extranet in an MPLS network facilitates secure connections between different organizations' private networks, not a general mechanism for providing internet access to internal SD-WAN WAN Edge routers.

TLOC extensions are a critical feature in Cisco SD-WAN (Viptela) that enable a WAN Edge router with a direct Internet connection to advertise this capability to the vSmart controller. This allows other WAN Edge routers in the fabric to forward internet-bound traffic to that specific WAN Edge, effectively centralizing or regionalizing internet access.