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Enabling IGMP snooping fast-leave processing
The fast-leave processing feature enables the IGMP snooping-enabled router to process IGMP leave
messages quickly. With this feature enabled, when the IGMP snooping-enabled router 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 IGMP snooping-enabled router 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 fast-leave processing to save bandwidth and
resources. However, on a port that has multiple hosts attached, you should not enable fast-leave
processing if you have enabled dropping unknown multicast data globally or for the port. 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 for 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 for 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, and might
further cause network interruption.
To solve these problems, disable that router port from becoming a dynamic router port after the port
receives an IGMP general query or a PIM hello message, so as to improve network security and the
control over multicast users.