User's Manual

Configuration Guide of XGS-5240-Series
42-5
1. Enhance efficiency: reduce network traffic, lighten the load of server and CP
U
2. Optimize performance: reduce redundant traffic
3. Distributed application: Enable Multipoint Application
42.1.2 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 a
ddress field of an IP message. In the process of Unicast data transmission, the transmi
ssion 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 envir
onment, the destination addresses is a group instead of a single one, they form a grou
p address. All message receivers will join in a group, and once they do, the data flowi
ng to the group address will be sent to the receivers immediately and all members in t
he 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 addr
esses are assigned officially; they are called Permanent Multicast Group. Permanent Mu
lticast 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 Mul
ticast addresses which are not kept for use by Permanent Multicast Group can be utiliz
ed by temporary Multicast groups.
224.0.0.0～224.0.0.255 are reserved Multicast addresses (Permanent Group Addres
s), address 224.0.0.0 is reserved but not assigned, and other addresses are used by R
outing 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 i
n 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