Hirschmann RS20 User Manual page 122

Network Load Control
Known Multicasts
In this frame you can determine how the device in IGMP mode sends
packets with known MAC/IP Multicast addresses that were learned
through IGMP Snooping.
 "Send to query and registered ports".
The device sends the packets with a known MAC/IP Multicast
address to all query ports and to registered ports.
This standard setting sends all Multicasts to all query ports and to
registered ports. The advantage of this is that it works in most
applications without any additional configuration.
Application: "Flood and Prune" routing in PIM-DM.
 "Send to registered ports".
The device sends the packets with a known MAC/IP Multicast
address to registered ports.
The advantage of this setting, which deviates from the standard, is
that it uses the available bandwidth optimally through direct
distribution. It requires additional port settings.
Application: Routing protocol PIM-SM.
Settings per Port (Table)

 "IGMP on"
This table column enables you to enable/disable the IGMP for each
port when the global IGMP Snooping is enabled. Port registration
will not occur if IGMP is disabled.
122
8.2 Multicast Application
UM BasicConfig L2E
Release 8.0 05/2013