A method for processing multicast data packets has steps for (a) requesting a second router upstream router by a multiple-processor data router to join a multicast group, the request including identification of a single physical ingress port from a plurality of available ports for receiving the multicast data packets; (b) preparing a multicast forwarding information base (MFIB) limited to only forwarding information incorporating the identified physical ingress port, and distributing the MFIB to a client software module hosting the identified physical ingress port; (c) receiving the multicast data packets at the identified ingress port; and (d) using only the MFIB to route the received multicast data packets.