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A multicast address, also called a group address, is a single IP address for a set of hosts that are joined in a multicasting group. An IP (Internet protocol) address is a unique numeric identifier for a computer or other device on a TCP/IP (transmission control protocol/Internet protocol) network. A multicast is a single stream of data (i.e., a set of packets) that is transmitted simultaneously to selected multiple hosts which have joined the multicast group. A host is a computer that is connected to the network. Officially designated multicast addresses range from 224.0.0.0 to 239.255.255.255. Some, termed well-known addresses, have been designated for specific uses. For example, 224.0.0.1 is the address for transmitting to all hosts in the multicasting group, and 224.0.0.2 is the multicasting address for all routers on the subnet (i.e., logical division of a network). OSPF (open shortest path first), an interior gateway protocol (IGP), uses 224.0.0.5 and 224.0.0.6 to send OSPF routing information to all OSPF routers on a network segment, and RIP (routing information protocol), another IGP, uses 224.0.0.9 to send routing information to all RIPv2 routers on a network segment. Created November 23, 2005. |