3Com 7700 Configuration Manual page 119

Ranges and meanings of Class D addresses are shown in Table 1.
Table 1 Ranges and Meanings of Class D Addresses
Class D address range
224.0.0.0∼224.0.0.255
224.0.1.0∼238.255.255.255
239.0.0.0∼239.255.255.255
Reserved multicast addresses that are commonly used are shown Table 2:
Table 2 Reserved Multicast Address List
Class D address
224.0.0.0
224.0.0.1
224.0.0.2
224.0.0.3
224.0.0.4
224.0.0.5
224.0.0.6
224.0.0.7
224.0.0.8
224.0.0.9
224.0.0.10
224.0.0.11
224.0.0.12
224.0.0.13
224.0.0.14
224.0.0.15
224.0.0.16
224.0.0.17
224.0.0.18
......
Ethernet Multicast MAC Addresses
When unicast IP packets are transmitted in Ethernet, the destination MAC address
is the MAC address of the receiver. However, when multicast packets are
transmitted, the destination is no longer a specific receiver but a group with
unspecific members. Therefore, the multicast MAC address should be used.
Multicast MAC addresses correspond to multicast IP addresses. IANA (Internet
Assigned Number Authority) stipulates that the higher 24 bits of the multicast
MAC address are 0x01005e and the lower 23 bits of the MAC address are the
lower 23 bits of the multicast IP address.
Meaning
Reserved multicast addresses (addresses of permanent
groups). Address 224.0.0.0 is reserved. The other addresses
can be used by routing protocols.
Multicast addresses available for users (addresses of
temporary groups). They are valid in the entire network.
Multicast addresses for local management. They are valid only
in the specified local range.
Meaning
Base Address (Reserved)
Addresses of all hosts
Addresses of all multicast routers
Unassigned
DVMRP routers
OSPF routers
OSPF DR (designated router)
ST routers
ST hosts
RIP-2 routers
IGRP routers
Mobile agents
DHCP server/Relay agent
All PIM routers
RSVP encapsulation
All CBT routers
Designated SBM
All SBMS
VRRP
......
IP Multicast Overview 111