3Com 5500 SI - Switch - Stackable, Руководство по настройке

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IP Multicast Overview 311
Ranges and meanings of Class D addresses are shown in Table 306
Reserved multicast addresses that are commonly used are shown in Table 307.
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 is 0x01005e and the
lower 23 bits of the MAC address is the lower 23 bits of the multicast IP address.
Table 306 Ranges and meaning 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.
Table 307 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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