User's Manual

C HAPTER 4 | Configuring the Switch
IGMP Snooping
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PARAMETERS
These parameters are displayed:
Global Configuration
◆ Snooping Enabled - When enabled, the switch will monitor network
traffic to determine which hosts want to receive multicast traffic.
(Default: Enabled)
This switch can passively snoop on IGMP Query and Report packets
transferred between IP multicast routers/switches and IP multicast host
groups to identify the IP multicast group members. It simply monitors
the IGMP packets passing through it, picks out the group registration
information, and configures the multicast filters accordingly.
◆ Unregistered IPMC Flooding Enabled - Floods unregistered
multicast traffic into the attached VLAN. (Default: Disabled)
Once the table used to store multicast entries for IGMP snooping is
filled, no new entries are learned. If no router port is configured in the
attached VLAN, and Unregistered IPMC Flooding is disabled, any
subsequent multicast traffic not found in the table is dropped,
otherwise it is flooded throughout the VLAN.
◆ IGMP SSM Range - IGMP Source-Specific Multicast range.
(Default: 232.0.0.0/8)
IPv4 addresses in the 232.0.0.0 to 232.255.255.255 range are
currently designated by RFC 4607 as SSM destination addresses and
are reserved for use by source-specific applications and protocols.
SSM-aware hosts and routers running the SSM service model can pass
traffic for any group within the specified address range.
When using IGMPv3 snooping (see the Compatibility parameter under
"Configuring VLAN Settings for IGMP Snooping and Query"), service
requests from IGMP Version 1, 2 or 3 hosts are all forwarded to the
upstream router as IGMPv3 reports. The primary enhancement
provided by IGMPv3 snooping is in keeping track of information about
the specific multicast sources which downstream IGMPv3 hosts have
requested or refused. The switch maintains information about both
multicast groups and channels, where a group indicates a multicast
flow for which the hosts have not requested a specific source (the only
option for IGMPv1 and v2 hosts unless statically configured on the
switch as described under "Configuring IGMP Filtering"), and a channel
indicates a flow for which the hosts have requested service from a
specific source. For IGMPv1/v2 hosts, the source address of a channel
is always null (indicating that any source is acceptable), but for IGMPv3
hosts, it may include a specific address when requested.
Only IGMPv3 hosts can request service from a specific multicast source.
When downstream hosts request service from a specific source for a
multicast service, these sources are all placed in the Include list, and
traffic is forwarded to the hosts from each of these sources. IGMPv3
hosts may also request that service be forwarded from any source
except for those specified. In this case, traffic is filtered from sources in
the Exclude list, and forwarded from all other available sources.