Hirschmann MS30, Power MICE, MACH 4000, OCTOPUS User Manual page 111

Traffic control 8.2 Multicast application
8.2.4 Description GMRP
The GARP Multicast Registration Protocol (GMRP) describes how multicast
information is distributed to other Switches on layer 2 level. This makes it
possible for Switches to learn multicast addresses. When a Multicast
address is entered in the static address table, the Switch sends this informa-
tion to all the ports. This tells the connected Switches to pass this multicast
address onto this Switch.
The GARP Multicast Registration Protocol (GMRP) describes the distribution
of data packets with a multicast address as the target address on layer 2.
Devices that want to receive data packets with a multicast address as the
target address carry out the registration of the multicast address with the aid
of the GMRP. For a Switch, registration involves entering the multicast
address in the filter table. When a multicast address is entered in the filter
table, the Switch sends this information in a GMRP packet to all the ports.
Therefore the connected Switches know that they have to send this multicast
address to this Switch. The GMRP enables packets with a multicast address
in the target address field to be sent to the ports entered. The other ports are
not affected by these packets.
Data packets with unregistered multicast addresses are transmitted to all
ports by the Switch.
Default setting: "Global Configuration": disabled.
Devices that do not support GMRP can be integrated into the multicast
adressing scheme by means of a static filter address entry on the connector
port.
The multicast tree is set up within 5 seconds in a network of up to 20 Switches
(200 ms per Switch), after the multicast- address has been entered for the
first time at a Switch port. This time period depends on the Join Time that is
set (default 200 ms).
Layer 2 Enhanced with Layer 2 Professional
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Release 1.0 10/05