Apparatus, and an associated method for facilitating routing of a datagram sourced at a content source to a mobile node. The mobile node is selectably operable in a heterogeneous network having two or more network parts operable pursuant to different operating protocols. An ARP broadcast is generated either gratuitously or by proxy mechanism on behalf of the mobile by the GGSN, Access Router or by the Home Agent indicating the network element that is responsible for forwarding of datagrams to the mobile and thereby implying the network part with which the mobile node is resident. And, the datagram is forwarded from the gateway network to the network element that is responsible for forwarding of datagrams to the mobile node. The datagrams are then routed through the network part identified by the broadcast to be the network part with which the mobile node is resident.