ECS3510-26P_Management Guide R02

C HAPTER 17 | Multicast Filtering
Layer 2 IGMP (Snooping and Query)
– 475 –
◆ 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 specific queries are
not 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membership information learned by switch may be out of date.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.
◆ TCN Query Solicit – Sends out an IGMP general query solicitation
when a spanning tree topology change notification (TCN) occurs.
(Default: Disabled)