What is IP Multicast?

Multicast is a network protocol which allows a single network packet to be delivered to a group of network ‘receiver’ nodes.

How is a multicast address defined?

(How are IP multicast receiving nodes addressed?)

Any Ethernet, or other 802.x, address with a high-order bit set to 1 (that is, its first octet is odd) is multicast, except for the broadcast address (which is all ones).

All IP addresses in the range 224.0.0.0 to 239.255.255.255 (224/4) have been reserved for multicast.

IANA has reserved several specific addresses for particular multicast applications.