Multimedia Traffic Control with IP Multicast (IGMP)
How IGMP Operates
“X” member on that port. If the port does not receive a join request for that
group within the forced-leave interval, the switch then blocks any further
group “X” traffic to the port.
Configuring Forced Fast-Leave IGMP
Syntax: [no] vlan < vid > ip igmp forcedfastleave <port-list>
Enables IGMP Forced Fast-Leave on the specified ports in the
selected VLAN, even if they are cascaded. (Default: Disabled.)
The no form of the command disables Forced Fast-Leave on the
specified ports in the selected VLAN. Use show running to
display the ports per-VLAN on which Forced Fast-Leave is
enabled.
To view a non-default IGMP forced fast-leave configuration on a VLAN, use
the show running-config command. (The show running-config output does not
include forced fast-leave if it is set to the default of 0.)
Forced fast-leave can be used when there are multiple devices attached to a
port.
Configuring Delayed Group Flush
When enabled, this feature continues to filter IGMP groups for a specified
additional period of time after IGMP leaves have been sent. The delay in
flushing the group filter prevents unregistered traffic from being forwarded
by the server during the delay period. In practice, this is rarely necessary on
the switches covered in this guide, which support data-driven IGMP. (Data-
Driven IGMP, which is enabled by default, prunes off any unregistered IGMP
streams detected on the switch.)
Syntax: igmp delayed-flush < time-period >
Where leaves have been sent for IGMP groups, enables the switch
to continue to flush the groups for a specified period of time.
This command is applied globally to all IGMP-configured
VLANs on the switch. Range: 0 - 255; Default: Disabled (0).
Syntax: show igmp delayed-flush
Displays the current igmp delayed-flush setting.
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