The VRF receive feature is the mechanism that fits the constraint when the customer does not want BGP, VRF-Lite links, or static routing for the inter-VRF requirement. Inter-VRF connectivity is normally achieved through route leaking with MP-BGP, static routes, firewall interfaces in each VRF, or VRF-Lite handoff links. The question explicitly excludes those common approaches and asks for a mechanism on the core network layer. The VRF receive capability allows selected traffic received on a global routing interface to be associated with a VRF context for locally configured addresses, supporting limited interaction without building a full routing exchange between the global table and the VRF. Policy-based routing with a global set statement can solve some forwarding cases, but it is not the specific mechanism described by the option set. A route map with import features would typically depend on route leaking behavior. Therefore, the best answer is the VRF receive feature under the global routing interfaces. Reference topics: VRF, inter-VRF routing, VRF receive, route leaking alternatives, core-layer segmentation.