Abstract— As stateful flow-aware services are becoming commonplace, distributed router architectures have to quickly assign packets being forwarded to service-specialized processors in order to balance flow processing and state among them. Moreover, packets belonging to the same flow must be always assigned to the same CPU, even if some of the service processors become unavailable. This paper presents two novel Fast Robust Hashing algorithms for persistent Flow-to-CPU mapping, that require less hashing operations per packet than previous Robust Hash algorithms, thus being able to fulfill all the above requirements to implement flow-aware services at wire-speed.