H3C Technologies H3C S3100V2 Series Switches - Manual (Page 77)

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Configuring fast leave processing
The fast leave processing feature enables the switch to process MLD done messages quickly. When the
fast leave processing feature is enabled and the switch receives an MLD done message on a port, the
switch immediately removes that port from the outgoing port list of the forwarding table entry for the
indicated IPv6 multicast group. Then, when receiving MLD done multicast-address-specific queries for
that IPv6 multicast group, the switch will not forward them to that port.
In VLANs where only one host is attached to each port, fast leave processing helps improve bandwidth
and resource usage. However, if fast leave processing is enabled on a port to which more than one host
is attached, when one host leaves a multicast group, the other hosts attached to the port and interested
in the same multicast group will fail to receive multicast data for that group. Therefore, if the function of
dropping unknown IPv6 multicast traffic is already enabled on the switch or in the VLANs, you should not
enable the fast leave processing function.
Configuring fast leave processing globally
Follow these steps to configure fast leave processing globally:
To do... Use the command... Remarks
Enter system view system-view —
Enter MLD snooping view mld-snooping —
Enable fast leave processing fast-leave [ vlan vlan-list ]
Required
Disabled by default
Configuring fast leave processing on a port or a group of ports
Follow these steps to configure fast leave processing on a port or a group of ports:
To do... Use the command... Remarks
Enter system view system-view —
interface interface-type
interface-number
Enter Ethernet interface/Layer 2
aggregate interface view or port
group view
port-group manual
port-group-name
Required
Use either approach
Enable fast leave processing
mld-snooping fast-leave [ vlan
vlan-list ] Required
Disabled by default
Disabling a port or a group of ports from changing into
dynamic router ports
At present, the following problems exist in a multicast access network:
• After receiving an MLD general query or IPv6 PIM Hello message from a connected host, a switch
port becomes a dynamic router port. Before its timer expires, this dynamic router port will receive all
multicast packets within the VLAN it belongs to and forward then to the host, thus affecting normal
multicast reception of the host.
• In addition, the MLD general query and IPv6 PIM Hello message sent from the host affects the
multicast routing protocol state on Layer 3 devices, such as the MLD querier or DR election, and
might further cause network interruption.