SNR S2940-8G-v2, Configuration Manual

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SNR S2940-8G-v2 Switch Configuration Guide
IPv4 Multicast Protocol
40.1.2 Multicast Address
The destination address of Multicast message uses class D IP address with range from 224.0.0.0
to 239.255.255.255. D class address can not appear in the source IP address field of an IP
message. In the process of Unicast data transmission, the transmission path of a data packet
is from source address routing to destination address, and the transmission is performed with
hop-by-hop principle. However, in IP Multicast environment, the destination addresses is a group
instead of a single one, they form a group address. All message receivers will join in a group, and
once they do, the data flowing to the group address will be sent to the receivers immediately and
all members in the group will receive the data packets. The members in a Multicast group are
dynamic, the hosts can join and leave the Multicast group at any time.
Multicast group can be permanent or temporary. Some of the Multicast group addresses are
assigned officially; they are called Permanent Multicast Group. Permanent Multicast Group keeps
its IP address fixed but its member structure can vary within. The member amount of Permanent
Multicast Group can be arbitrary, even zero. The IP Multicast addresses which are not kept for
use by Permanent Multicast Group can be utilized by temporary Multicast groups.
224.0.0.0 - 224.0.0.255 are reserved Multicast addresses (Permanent Group Address), ad-
dress 224.0.0.0 is reserved but not assigned, and other addresses are used by Routing Protocol;
224.0.1.0 - 238.255.255.255 are Multicast addresses available to users (Temporary Group Ad-
dress) 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
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