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BLADEOS 6.5.2 Application Guide
BMD00220, October 2010 Chapter 18: Internet Group Management Protocol 251
IGMP Groups
The G8124 supports a maximum of 1000 IGMP entries, on a maximum of 1024 VLANs.
One IGMP entry is allocated for each unique join request, based on the VLAN and IGMP group
address. If multiple ports join the same IGMP group using the same VLAN, only a single IGMP
entry is used.
FastLeave
In normal IGMP operation, when the switch receives an IGMPv2 leave message, it sends a
Group-Specific Query to determine if any other devices in the same group (and on the same port)
are still interested in the specified multicast group traffic. The switch removes the affiliated port
from that particular group, if the following conditions apply:
If the switch does not receive an IGMP Membership Report within the query-response-interval.
If no multicast routers have been learned on that port.
With FastLeave enabled on the VLAN, a port can be removed immediately from the port list of the
group entry when the IGMP Leave message is received, unless a multicast router was learned on the
port.
Enable FastLeave only on VLANs that have only one host connected to each physical port. To
enable FastLeave, use the following command:
IGMPv3 Snooping
IGMPv3 includes new membership report messages to extend IGMP functionality. The switch
provides snooping capability for all types of IGMP version 3 (IGMPv3) Membership Reports.
IGMPv3 supports Source-Specific Multicast (SSM). SSM identifies session traffic by both source
and group addresses.
The IGMPv3 implementation keeps records on the multicast hosts present in the network. If a host
is already registered, when it receives a new IS_INC/TO_INC/IS_EXC/TO_EXC report from same
host, the switch makes the correct transition to new (port-host-group) registration based on the
IGMPv3 RFC. The registrations of other hosts for the same group on the same port are not changed.
RS G8124(config)# ip igmp snoop vlan <VLAN number> fast-leave