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Enabling IGMP snooping fast-leave processing
IGMP snooping fast-leave processing feature enables the switch to process IGMP leave messages
quickly. With IGMP snooping feature enabled, when the switch receives an IGMP leave message on
a port, it immediately removes that port from the forwarding entry for the multicast group specified in
the message. Then, when the switch receives IGMP group-specific queries for that multicast group,
it does not forward them to that port.
On a port that has only one host attached, you can enable IGMP snooping fast-leave processing to
save bandwidth and resources. However, on a port that has multiple hosts attached, do not enable
IGMP snooping fast-leave processing if dropping unknown multicast data is enabled. Otherwise, if a
host on the port leaves a multicast group, the other hosts attached to the port in the same multicast
group cannot receive the multicast data for the group.
Enabling IGMP snooping fast-leave processing globally
Step Command
Remarks
1.
Enter system view.
system-view
N/A
2.
Enter IGMP-snooping view.
igmp-snooping
N/A
3.
Enable IGMP snooping
fast-leave processing.
fast-leave
[
vlan
vlan-list
]
Disabled by default.
Enabling IGMP snooping fast-leave processing on a port
Step Command Remarks
1.
Enter system view.
system-view
N/A
2.
Enter Layer 2 Ethernet
interface view or Layer 2
aggregate interface view, or
enter port group view.
•
Enter Layer 2 Ethernet interface view
or Layer 2 aggregate interface view:
interface
interface-type
interface-number
•
Enter port group view:
port-group
manual
port-group-name
Use either command.
3.
Enable IGMP snooping
fast-leave processing on the
port.
igmp-snooping
fast-leave
[
vlan
vlan-list
]
Disabled by default.
Disabling a port from becoming a dynamic router port
The following problems might exist in a multicast access network:
•
After receiving an IGMP general query or a PIM hello message from a connected host, a router
port becomes a dynamic router port. Before its timer expires, this dynamic router port receives
all multicast packets within the VLAN where the port belongs, and forwards them to the host,
affecting normal multicast reception of the host.
•
In addition, the IGMP general query or PIM hello message that the host sends affects the
multicast routing protocol state on Layer 3 devices, such as the IGMP querier or DR election.
This might further cause network interruption.
To solve these problems, after the router port receives an IGMP general query or a PIM hello
message, disable the port from becoming a dynamic router port. This enhances network security and
the control over multicast users.
