SNR S2989G-24TX-POE [252/553] Ip multicast packet transmission

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S2989G-24TX Operation Manual

Chapter 5 Multicast Protocol Related Configuration

4-27

by Routing Protocol; 224.0.1.0～238.255.255.255 are Multicast addresses available to

users（Temporary Group Address） and are valid in the entire domain of the network;

239.0.0.0～239.255.255.255 are local management Multicast addresses, which are valid

only in specific local domain. Frequently used reserved multicast address list is as follows:

Benchmark address (reserved)

224.0.0.1 Address of all hosts

224.0.0.2 Address of all Multicast Routers

224.0.0.3 Unassigned

224.0.0.4 DVMRP Router

224.0.0.5 OSPF Router

224.0.0.6 OSPF DR

224.0.0.7 ST Router

224.0.0.8 ST host

224.0.0.9 RIP-2 Router

224.0.0.10 IGRP Router

224.0.0.11 Active Agent

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 Specified SBM

224.0.0.17 All SBMS

224.0.0.18 VRRP

224.0.0.22 IGMP

When Ethernet transmits Unicast IP messages, the destination MAC address it uses

is the receiver’s MAC address. But in transmitting Multicast packets, the transmission

destination is not a specific receiver any more, but a group with uncertain members, thus

Multicast MAC address is used. Multicast MAC address is corresponding to Multicast IP

address. It is prescribed in IANA (Internet Assigned Number Authority) that the higher 25

bits in Multicast MAC address is 0x01005e, and the lower 23bits in MAC address is the

lower 23bits in Multicast IP address.

Since only 23bits out of the lower 28bits in IP Multicast address are mapped into MAC

address, therefore there are 32 IP Multicast addresses which are mapped into the same

MAC address.

5.1.3

IP Multicast Packet Transmission

In Multicast mode, the source host sends packets to the host group indicated by the

Multicast group address in the destination address field of IP data packet. Unlike Unicast