SpiNNaker is a hardware-based massively-parallel real-time universal neural network simulator designed to simulate large-scale spiking neural networks. Spikes are distributed across the system using a multicast packet router. Each packet represents an event (spike) generated by a neuron. On the basis of the source of the spike (chip, core and neuron), the routers distribute the network packet across the system towards the destination neuron(s). This paper describes a novel approach to the projection routing problem that shows advantages in both the size of the routing tables generated and the computational complexity for the generation of routing tables. To achieve this, spikes are routed on the basis of the source population, leaving to the destination core the duty to propagate the received spike to the appropriate neuron(s). © 2012 IEEE.