Methods and apparatus are disclosed for identifying the relevancy of packets. In one embodiment, source addresses are associated with network topology indications. When a packet is received, its network topology indication is compared with the corresponding one retrieved from a data structure to determine whether to drop the packet. Source addresses may also be associated with authorized interfaces to determine whether a packet was received on an authorized interface. In one embodiment, a maintained network topology indication is associated with a packet. After it is processed, the corresponding latest network topology indication is retrieved and compared with that previously associated with the packet. In one embodiment, upon a change in a network topology indication associated with an interface, control packets are placed in each of the queues corresponding to the destination interface, so it can be readily identified when this update has been propagated through the system.