3Com 4007, Implementation Manual, Page: 431 / 684

Key Concepts 431
Reserved MAC Addresses
IANA also controls a reserved portion of the IEEE-802 MAC-layer
multicast address space. All addresses in this block use hexadecimal
format and begin with 01-00-5E. A simple procedure maps Class D
addresses to this block, so that IP multicasting can take advantage of the
hardware-level multicasting supported by network interface cards (NICs).
The mapping process involves placing the low-order 23 bits of the Class D
address (binary format) into the low-order 23 bits of the MAC address
(hexadecimal format). For example, the Layer 3 address 224.10.8.5 maps
to the Layer 2 MAC address 01-00-5E
-0A-08-05 .
To send a multicast packet, a source station inserts the Class D address in
the IP packet, the network interface card maps that address to a IEEE-802
Ethernet multicast MAC address, and sends the frame. A host that wants
to receive packets that are addressed to this group notifies its IP layer as
such.
Table 78 Examples of Class D Permanent Address Assignments
Address Meaning
224.0.0.0 Base Address (Reserved)
224.0.0.1 All systems on this subnet
224.0.0.2 All routers on this subnet
224.0.0.4 All DVMRP routers
224.0.0.5 All OSPF routers
224.0.0.6 All OSPF designated routers
224.0.0.7 All ST routers
224.0.0.8 All ST hosts
224.0.0.9 All RIP version 2 routers
224.0.0.11 Mobile agents
224.0.0.12 DHCP server/relay agent
224.0.0.13 All PIM routers
224.0.0.14 RSVP, Encapsulation
224.0.0.15 All CBT routers