Each of several routers connected to a LAN elects the same router as the designated router for a multicast group identified by a multicast address. Each of the several routers implements a method for electing the designated router. The method includes in one embodiment, generating several values corresponding...http://www.google.com/patents/US7911977?utm_source=gb-gplus-sharePatent US7911977 - Designated router assignment per multicast group address/range
