Fast-Leave Igmp - SMC Networks SMC6624M Management Manual

Configuring Advanced Features
Multimedia Traffic Control with IP Multicast (IGMP)
on IGMP without IP addressing is that the switch cannot become Querier on
any VLANs for which it has no IP address—so the network administrator must
ensure that another IGMP device will act as Querier and that an additional
IGMP device is available as a backup Querier.
Table 9-11.IGMP Operation With or Without IP Addressing
IGMP Function Available With IP Addressing
Configured on the VLAN
Drop multicast group traffic for which there
have been no join requests from IGMP clients
connected to ports on the VLAN.
Forward multicast group traffic to any port on
the VLAN that has received a join request for
that multicast group.
Forward join requests (reports) to the Querier.
Configure individual ports in the VLAN to Auto
(the default)/Blocked, or Forward.
Configure IGMP traffic forwarding to normal or
high-priority forwarding.
Age-Out IGMP group addresses when the last
IGMP client on a port in the VLAN leaves the
group.
Support Fast-Leave IGMP (below) and Forced
Fast-Leave IGMP (page 9-100).
Support automatic Querier election.
Operate as the Querier.
Provide a backup Querier.

Fast-Leave IGMP

IGMP Operation Presents a "Delayed Leave" Problem. Where multi-
ple IGMP clients are connected to the same port on an IGMP device (switch
or router), if only one IGMP client joins a given multicast group, then later
sends a Leave Group message and ceases to belong to that group, the IGMP
device retains that IGMP client in its IGMP table and continues forwarding
IGMP traffic to the IGMP client until the Querier triggers confirmation that no
other group members exist on the same port. This means that the switch
continues to transmit unnecessary multicast traffic through the port until the
Querier renews multicast group status.
9-94
Available Operating Differences Without an IP Address
Without IP
Addressing?
Yes
Yes
Yes
Yes
Yes
Yes Requires that another IGMP device in the VLAN has an IP
address and can operate as Querier. This can be a multi-
cast router or another switch configured for IGMP oper-
ation. SMC recommends that the VLAN also include a
device operating as a backup Querier in case the device
Yes
operating as the primary Querier fails for any reason.
No Querier operation not available.
No Querier operation not available.
No Querier operation not available.
None
None
None
None
None