Switch 7700 Configuration Guide

IP Multicast Overview 111
Ranges and meanings of Class D addresses are shown in Table 1.
Reserved multicast addresses that are commonly used are shown Tab le 2:
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.
Tabl e 1 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.
Tabl e 2 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
224.0.0.5 OSPF routers
224.0.0.6 OSPF DR (designated router)
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
224.0.0.18 VRRP
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