3Com 10014298 manual Ranges and meanings of Class D addresses are shown in Table

IP Multicast Overview 111

A multicast group can be either permanent or temporary. Part of addresses in the multicast group are reserved by the IANA and are known as the permanent multicast group. IP addresses of a permanent group are unchanged, but the members in the group can change. The number of members in a permanent multicast group can be random or even 0. Those IP multicast addresses that are not reserved for permanent multicast groups can be used by temporary groups.

Ranges and meanings of Class D addresses are shown in Table 114.

Table 114 Ranges and Meanings of Class D Addresses

Class D address range	Meaning
224.0.0.0∼224.0.0.255	Reserved multicast addresses (addresses of
	permanent groups). Address 224.0.0.0 is
	reserved. The other addresses can be used by
	routing protocols.
224.0.1.0∼238.255.255.255	Multicast addresses available for users
	(addresses of temporary groups). They are
	valid in the entire network.
239.0.0.0∼239.255.255.255	Multicast addresses for local management.
	They are valid only in the specified local range.

Reserved multicast addresses that are commonly used are shown Table 115:

Table 115 Reserved Multicast Address List

Class D address	Meaning
224.0.0.0	Base Address (Reserved)
224.0.0.1	Addresses of all hosts
224.0.0.2	Addresses of all multicast routers
224.0.0.3	Unassigned
224.0.0.4	DVMRP routers
224.0.0.7	ST routers
224.0.0.8	ST hosts
224.0.0.9	RIP-2 routers
224.0.0.10	IGRP 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
224.0.0.16	Designated SBM
224.0.0.17	All SBMS
……	……

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