HP 6400cl, Management Manual, Page: 119 / 664

Multimedia Traffic Control with IP Multicast (IGMP)
How IGMP Operates
multicast traffic (for that group) to port A3. If the switch is not the Querier, it
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 4-3 belong to different VLANs, Fast-Leave does
not operate on port A6.
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
“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.
Configuration Options for Forced Fast-Leave
Feature Default Settings Function
Forced Fast- 2 1 (enabled) Uses the setmib command to enable or disable
Leave state (disabled)
2 (disabled) Forced Fast-Leave on individual ports. When
enabled on a port, Forced Fast-Leave operates only
if the switch detects multiple end nodes (and at least
one IGMP client) on that port.
N o t e o n V L A N
In the HP Procurve Series 5300XL switch, the walkmib and setmib com-
N u m b e r s
mands use an internal VLAN number (and not the VLAN ID, or VID) to display
or change many per-vlan features, such as the Forced Fast-Leave state.
Because the internal VLAN number for the default VLAN is always 1 (regard-
less of whether VLANs are enabled on the switch), and because a discussion
of internal VLAN numbers for multiple VLANs is beyond the scope of this
document, the discussion here concentrates on examples that use the default
VLAN.
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