Supermicro SSE-G2252 User Manual page 483

When IGMP snooping is disabled globally, snooping can still be configured per
VLAN interface, but the interface settings will not take effect until snooping is
re-enabled globally.
• Proxy Reporting Status – Enables IGMP Snooping with Proxy Reporting. (Default:
Disabled)
When proxy reporting is enabled with this command, the switch performs "IGMP
Snooping with Proxy Reporting" (as defined in DSL Forum TR-101, April 2006),
including last leave, and query suppression.
Last leave sends out a proxy query when the last member leaves a multicast group,
and query suppression means that neither specific queries nor general queries are
forwarded from an upstream multicast router to hosts downstream from this device.
When proxy reporting is disabled, all IGMP reports received by the switch are
forwarded natively to the upstream multicast routers.
• TCN Flood – Enables flooding of multicast traffic if a spanning tree topology change
notification (TCN) occurs. (Default: Disabled)
When a spanning tree topology change occurs, the multicast membership
information learned by switch may be out of date. For example, a host linked to one
port before the topology change (TC) may be moved to another port after the
change. To ensure that multicast data is delivered to all receivers, by default, an
switch in a VLAN (with IGMP snooping enabled) that receives a Bridge Protocol
Data Unit (BPDU) with TC bit set (by the root bridge) will enter into "multicast
flooding mode" for a period of time until the topology has stabilized and the new
locations of all multicast receivers are learned.
If a topology change notification (TCN) is received, and all the uplink ports are
subsequently deleted, a time out mechanism is used to delete all of the currently
learned multicast channels.
When a new uplink port starts up, the switch sends unsolicited reports for all
currently learned channels out the new uplink port.
By default, the switch immediately enters into "multicast flooding mode" when a
spanning tree topology change occurs. In this mode, multicast traffic will be flooded
to all VLAN ports. If many ports have subscribed to different multicast groups,
flooding may cause excessive packet loss on the link between the switch and the
end host. Flooding may be disabled to avoid this, causing multicast traffic to be
delivered only to those ports on which multicast group members have been learned.
Otherwise, the time spent in flooding mode can be manually configured to reduce
excessive loading.
When the spanning tree topology changes, the root bridge sends a proxy query to
quickly re-learn the host membership/port relations for multicast channels. The root
bridge also sends an unsolicited Multicast Router Discover (MRD) request to quickly
locate the multicast routers in this VLAN.
The proxy query and unsolicited MRD request are flooded to all VLAN ports except
for the receiving port when the switch receives such packets.
Chapter 18: Multicast Filtering
18-5