A one-to-many transmission of data over an IP network. It is used for myriad purposes including updating routers, announcing and discovering services and streaming media. IP multicast saves network bandwidth, because packets are transmitted as one stream over the backbone and only split apart to the target stations by the router at the end of the path. See
mDNS and
multicast.
Multicast Address Range
IP multicast packets are identified by using a destination address in a range from 224.0.0.0 to 224.0.0.255. The addresses within the range are reserved for specific purposes. For example, 224.0.0.1 means all nodes on the subnet, while 224.0.0.2 means all routers on the subnet. The address 224.0.0.251 is reserved for multicast DNS (mDNS), which is used to query devices for their capabilities. See
DVMRP,
MOSPF and
PIM.