Various systems and methods for preventing loops. For example, one method involves receiving a multicast data packet at a node. The node is coupled to a local area network (LAN). An internet protocol (IP) prefix is assigned to the LAN. The method involves determining whether a source address included in the packet is covered by the IP prefix. Depending on the direction of travel of the multicast data packet and whether or not the source address is covered by the IP prefix, the node determines whether a loop exists.