Planet Networking & Communication SGS-5240 Series User Manual page 111

is sent to the upstream multicast router. A reduced value will result in reduced time to detect the loss of the last member of a
group or source, but may generate more burst traffic. This attribute will take effect only if IGMP snooping proxy reporting is
enabled or IGMP querier is enabled .
◆Last Member Query Count – The number of IGMP proxy group specific or group-and-source-specific query messages that
are sent out before the system assumes there are no more local members.
(Range: 1-255; Default: 2)
This attribute will take effect only if IGMP snooping proxy reporting or IGMP querier is enabled.
◆Proxy Query Address – A static source address for locally generated query and report messages used by IGMP Proxy
Reporting.
(Range: Any valid IP unicast address; Default: 0.0.0.0)
IGMP Snooping uses a null IP address of 0.0.0.0 for the source of IGMP query messages which are proxied to downstream
hosts to indicate that it is not the elected querier, but is only proxying these messages as defined in RFC 4541. The switch also
uses a null address in IGMP reports sent to upstream ports. Many hosts do not implement RFC 4541, and therefore do not
understand query messages with the source address of 0.0.0.0. These hosts will therefore not reply to the queries, causing the
multicast router to stop sending traffic to them. To resolve this problem, the source address in proxies IGMP query messages
can be replaced with any valid unicast address (other than the router's own address). Rules Used for Proxy Reporting When
IGMP Proxy Reporting is disabled, the switch will use a null IP address for the source of IGMP query and report messages
unless a proxy query address has been set. When IGMP Proxy Reporting is enabled, the source address is based on the
following criteria:

If a proxy query address is configured, the switch will use that address as the source IP address in general and
group-specific query messages sent to downstream hosts, and in report and leave messages sent upstream from
the multicast router port.

If a proxy query address is not configured, the switch will use the VLAN's IP address as the IP source address in
general and group specific query messages sent downstream, and use the source address of the last IGMP
message received from a downstream host in report and leave messages sent upstream from the multicast router
port.
To show the interface settings for IGMP snooping:
User's Manual of SGS-5240 Series Managed Switch
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