Igmp Snooping; Igmp Groups; Igmpv3 Snooping - IBM RackSwitch G8000 Application Manual

IGMP Snooping

IGMP Groups

IGMPv3 Snooping

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RackSwitch G8000: Application Guide
IGMP Snooping allows a switch to listen to the IGMP conversation between hosts
and Mrouters. By default, a switch floods multicast traffic to all ports in a broadcast
domain. With IGMP Snooping enabled, the switch learns the ports interested in
receiving multicast data and forwards it only to those ports. IGMP Snooping
conserves network resources.
The switch can sense IGMP Membership Reports from attached hosts and acts as a
proxy to set up a dedicated path between the requesting host and a local IPv4
Mrouter. After the path is established, the switch blocks the IPv4 multicast stream
from flowing through any port that does not connect to a host member, thus
conserving bandwidth.
When the switch is in stacking mode, one IGMP entry is allocated for each unique
join request, based on the combination of the port, VLAN, and IGMP group address.
If multiple ports join the same IGMP group, they require separate IGMP entries,
even if using the same VLAN.
In stand-alone (non-stacking) mode, one IGMP entry is allocated for each unique
join request, based on the VLAN and IGMP group address only (regardless of the
port). If multiple ports join the same IGMP group using the same VLAN, only a single
IGMP entry is used.
IGMPv3 includes new Membership Report messages that extend IGMP
functionality. The switch provides snooping capability for all types of IGMPv3
Membership Reports.
IGMPv3 is supported in stand-alone (non-stacking) mode only.
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 sends an
IS_INC/TO_INC/IS_EXC/TO_EXC report, the switch overwrites the existing
(port-host-group) registration with the new registration; the registrations of other
hosts on the same group, same port are not changed. IS_INCLUDE/TO_INCLUDE
reports with no source are not registered.
The G8000 supports the following IGMPv3 filter modes:
• INCLUDE mode: The host requests membership to a multicast group and
provides a list of IPv4 addresses from which it wants to receive traffic.
• EXCLUDE mode: The host requests membership to a multicast group and
provides a list of IPv4 addresses from which it does not want to receive traffic.
This indicates that the host wants to receive traffic only from sources that are not
part of the Exclude list. To disable snooping on EXCLUDE mode reports, use the
following command:
RS G8000(config) # no ip igmp snoop igmpv3 exclude