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Chapter 24 Multicast
MGS3700-12C User’s Guide
248
24.6.1 Types of MVR Ports
In MVR, a source port is a port on the Switch that can send and receive multicast
traffic in a multicast VLAN while a receiver port can only receive multicast traffic.
Once configured, the Switch maintains a forwarding table that matches the
multicast stream to the associated multicast group.
24.6.2 MVR Modes
You can set your Switch to operate in either dynamic or compatible mode.
In dynamic mode, the Switch sends IGMP leave and join reports to the other
multicast devices (such as multicast routers or servers) in the multicast VLAN.
This allows the multicast devices to update the multicast forwarding table to
forward or not forward multicast traffic to the receiver ports.
In compatible mode, the Switch does not send any IGMP reports. In this case, you
must manually configure the forwarding settings on the multicast devices in the
multicast VLAN.
24.6.3 How MVR Works
The following figure shows a multicast television example where a subscriber
device (such as a computer) in VLAN 1 receives multicast traffic from the
streaming media server, S, via the Switch. Multiple subscriber devices can connect
through a port configured as the receiver on the Switch.
When the subscriber selects a television channel, computer A sends an IGMP
report to the Switch to join the appropriate multicast group. If the IGMP report
matches one of the configured MVR multicast group addresses on the Switch, an
entry is created in the forwarding table on the Switch. This maps the subscriber
VLAN to the list of forwarding destinations for the specified multicast traffic.
When the subscriber changes the channel or turns off the computer, an IGMP
leave message is sent to the Switch to leave the multicast group. The Switch
sends a query to VLAN 1 on the receiver port (in this case, a DSL port on the
Switch). If there is another subscriber device connected to this port in the same
subscriber VLAN, the receiving port will still be on the list of forwarding destination