In computer networking a multicast address is an identifier for a group of Servers that have joined a Multicast group.

= IP Multicast Addresses =

Within Internet Protocol it is historically known as a class D address, a type of IP address. It ranges from 224.0.0.0 to 239.255.255.255 or 224.0.0.0/4. Address assignments from within this range are specified in the internet engineering task force best current practice [ftp://ftp.isi.edu/in-notes/bcp/bcp51.txt document] also known as RFC 3171.

The 224.0.0.0 to 224.0.0.255 range is assigned to multicasting on the local Local area network only. Well known examples are Routing Information Protocol which uses 224.0.0.9 and Open Shortest Path First which uses 224.0.0.5.

The following table is a partial list of well-known Class D addresses that are reserved for IP multicasting and registered with the Internet Assigned Numbers Authority (IANA).

For a full and current listing of additional IP addresses that are reserved for multicasting, see the [http://www.iana.org/assignments/multicast-addresses Internet Multicast Addresses Web site].

The 233.0.0.0/8 range has been assigned by RFC 2770 as public multicast address space that is aligned along autonomous system (Internet) number allocations. Each byte of the AS number corresponds to the second and third Octets of the multicast address.

The 239.0.0.0/8 range has been assigned by RFC 2365 as a locally administered address space with local or organizational scope.

For advice on choosing multicast addresses for use in your application, see [http://www.29west.com/docs/THPM/multicast-address-assignment.html this page on multicast address assignment].

= Ethernet Multicast Addresses =

Some well known Ethernet multicast addresses: