Specifications

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 Multicast Router (or the Layer 3 Multicast Device): The router or switch that supports the layer
3 multicast functions, which contains the multicast routing function and the management
function of the multicast group members.
The multicast model divides into two types depending on whether there is an exact multicast
source: ASM (Any-Source Multicast) and SSM (Source-Specific Multicast).
ASM (Any-Source Multicast): In the ASM model, any sender can be a multicast source sending
multicast information to a multicast group address, and receivers can join a multicast group
identified by the group address and obtain multicast information addressed to that multicast group.
In this model, receivers are not aware of the location of the multicast source in advance. However,
they can join or leave the multicast group at any time. At any specified moment, the number of
multicast source in the ASM should be no more than one, otherwise network congestion and
malfunction of the multicast members may occur.
SSM (Source-Specific Multicast): In the SSM model, the receivers know the exact location of the
multicast source. The SSM allows host to specify the multicast sources and it uses the multicast
group address range different from that of the ASM. The SSM marks a multicast session with both
multicast address and multicast source address, and it builds up dedicated multicast forwarding
path for the receiver and its specified multicast source.
11.1 Global Config
The Global Config can be implemented on the Global Config and Mroute Table pages.
11.1.1 Global Config
You must enable IP multicast routing. Then the software can forward multicast packets, and the
switch can populate its multicast routing table.
Choose the menu Multicast Routing→Global Config→Global Config to load the following
page.
Figure 11-1 Multicast Global Config
The following entries are displayed on this screen:

Multicast Global Config
Multicast Routing: S
elect Enable/Disable Multicast Routing function globally on
the switch. The default is "disable".
SG Expiry Timer:
SG Expiry Timer is used to adjust (S, G) expiry timer interval
for (S, G) multicast routers. The range is from 60 to 65535
seconds.
Spt-threshold: Select rate which the last-
hop router will switch to a
source-
specific shortest path tree. Specify infinity if you want
all sources for the specified group to use the shared tree,
never switching to the source tree. The default is 0 kbps.