HP 2610-PWR - Manual (Page 100)

Multimedia Traffic Control with IP Multicast (IGMP)
How IGMP Operates
Querier's processing of that Leave. For more on this topic, refer to “Forced
Fast-Leave IGMP” on page 4-17.
ProCurve recommends that the following settings be used.
■ Use Delayed Group Flush on the Series 2610 switches whenever Fast
Leave or Forced Fast Leave are set on a port (see page 4-17).
■ Forced fast leave can be used when there are multiple devices
attached to a port.
Automatic Fast-Leave Operation. If a switch port is:
a. Connected to only one end node
b. The end node currently belongs to a multicast group; i.e. is an IGMP
client
c. The end node subsequently leaves the multicast group
Then the switch does not need to wait for the Querier status update interval,
but instead immediately removes the IGMP client from its IGMP table and
ceases transmitting IGMP traffic to the client. (If the switch detects multiple
end nodes on the port, automatic Fast-Leave does not activate—regardless of
whether one or more of these end nodes are IGMP clients.)
In the next figure, automatic Fast-Leave operates on the switch ports for IGMP
clients “3A” and “5A”, but not on the switch port for IGMP clients “7A” and 7B,
Server “7C”, and printer “7D”.
Routing
Switch
Acting as
Querier
ProCurve Switch with
Automatic Fast-Leave
Server
7C
Switch 7X
3A 5A
7A
Fast-Leave IGMP
automatically operates
on the ports connected
to IGMP clients 3A and
5A, but does not
operate on the port
connected to Switch 7X
Fast-Leave IGMP does
not activate on this port.
Fast-Leave IGMP
activates on these
two ports.
A1 A3 A4 A6
Printer
7D
7B
Figure 4-3. Example of Automatic Fast-Leave IGMP Criteria
When client “3A” running IGMP is ready to leave the multicast group, it
transmits a Leave Group message. Because the switch knows that there is only
one end node on port A3, it removes the client from its IGMP table and halts
multicast traffic (for that group) to port A3. If the switch is not the Querier, it
4-16