PLANET SGSD-1022 - Manual (Page 211)

User’s Manual of SGSD-1022 / SGSD-1022P
SGSW-2840 / SGSW-2840P
When using IGMPv3 snooping, 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), and a channel indicates a flow for
which the hosts have requested service from a specific source.
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 all sources except for those specified. In
this case, traffic is filtered from sources in the Exclude list, and forwarded from all other available sources.
1. When the Managed Switch is configured to use IGMPv3 snooping, the snooping
version may be downgraded to version 2 or version 1, depending on the version of the
IGMP query packets detected on each VLAN.
2. IGMP snooping will not function unless a multicast router port is enabled on the
switch. This can be accomplished in one of two ways. A static router port can be
manually configured (see “ Specifying Static Interfaces for a Multicast Router ” ).
Using this method, the router port is never timed out, and will continue to function until
explicitly removed. The other method relies on the switch to dynamically create
multicast routing ports whenever multicast routing protocol packets or IGMP query
packets are detected on a port.
3. A maximum of up to 255 multicast entries can be maintained for IGMP snooping, and
255 entries for Multicast Routing, when both of these features are enabled. If the
table’s capacity is exceeded, the IGMPv3 snooping will not support multicast source
filtering, but will forward multicast traffic from all relevant sources to the requesting
hosts.
Static IGMP Router Interface – If IGMP snooping cannot locate the IGMP querier, you can manually designate a known IGMP
querier (i.e., a multicast router/switch) connected over the network to an interface on your switch. This interface will then join all
the current multicast groups supported by the attached router/switch to ensure that multicast traffic is passed to all appropriate
interfaces within the switch.
Static IGMP Host Interface – For multicast applications that you need to control more carefully, you can manually assign a
multicast service to specific interfaces on the switch.
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