A router operates in both a Segment Routing (SR) network portion and a Multiprotocol Label Switching (MPLS) network portion of a network that utilizes Open Shortest Path First (OSPF). The router receives an OSPF advertisement message originated by a mapping server that includes a sub-Type-length-value (sub-TLV) element that identifies a preferred type of path across the MPLS network portion for an identifiable set of traffic that is to be received by the router from the SR network portion. The router identifies, based at least in part upon the sub-TLV element, one path of a plurality of available paths across the MPLS network portion for the identifiable set of traffic, and configures its forwarding plane to utilize the identified one path accordingly for the identifiable set of traffic. The OSPF advertisement message can be an OSPF LSA, and can carry an Extended Prefix Range TLV including the sub-TLV element.