An efficient Reverse Path Forwarding (RPF) check mechanism is disclosed. In one embodiment, when a network node receives a multicast packet on an incoming interface, the network node obtains an expected incoming interface identifier from either a unicast routing table or a multicast forwarding information table. A RPF Flag stored in association with multicast flow information determines from which table the interface identifier is obtained. If the expected incoming interface does not match the actual incoming interface, the multicast packet is discarded.