Multimedia Traffic Control with IP Multicast (IGMP)

How IGMP Operates

does not wait for the actual Querier to verify that there are no other group members on port A3. If the switch itself is the Querier, it does not query port A3 for the presence of other group members.

Note that Fast-Leave operation does not distinguish between end nodes on the same port that belong to different VLANs. Thus, for example, even if all of the devices on port A6 in figure 4-3belong to different VLANs, Fast-Leave does not operate on port A6.

Using Delayed Group Flush

This feature continues to filter IGMP-Left groups for a specified additional period of time. The delay in flushing the group filter prevents stale traffic from being forwarded by the server. Delayed Group Flush is enabled or disabled for the entire switch.

ProCurve recommends that Delayed Group Flush be used whenever Fast Leave or Forced Fast Leave are enabled on the Series 2610 and 2610-PWR Switches. Note that this command must be executed in the configuration context of the CLI.

Syntax: igmp delayedflush <time period>

Enables the switch to continue to flush IGMP-Left groups for a specified period of time (0 - 255 seconds). The default setting is Disabled. To disable, reset the time period to zero.

Syntax: show igmp delayedflush

Displays the current setting for the switch.

Forced Fast-Leave IGMP

Forced Fast-Leave IGMP speeds up the process of blocking unnecessary IGMP traffic to a switch port that is connected to multiple end nodes. (This feature does not activate on ports where the switch detects only one end node). For example, in figure 4-3,even if you configured Forced Fast-Leave on all ports in the switch, the feature would activate only on port A6 (which has multiple end nodes) when a Leave Group request arrived on that port.

When a port having multiple end nodes receives a Leave Group request from one end node for a given multicast group “X”, Forced Fast-Leave activates and waits a small amount of time to receive a join request from any other group

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