H3C Technologies H3C S10500 Series Switches - Manual (Page 273)

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Timer Description Message before expiry Action after expiry
Dynamic member
port aging timer
When a port dynamically joins
an IPv6 multicast group, the
switch sets a timer for the port,
which is initialized to the
dynamic member port aging
time.
MLD report message.
The switch removes this
port from the MLD
snooping forwarding
table.
NOTE:
The port aging mechanism of MLD snooping works only for dynamic ports; a static port will never age out.
How MLD snooping works
A switch that runs MLD snooping performs different actions when it receives different MLD messages, as
follows:
NOTE:
The description about adding or deleting a port in this section is only for a dynamic port. Static ports can
be added or deleted only through the corresponding configurations. For more information, see
“ Configuring static ports .”
General queries
The MLD querier periodically sends MLD general queries to all hosts and routers (FF02::1) on the local
subnet to determine whether IPv6 multicast group members exist on the subnet.
After receiving an MLD general query, the switch forwards it through all ports in the VLAN except the port
that received the MLD query. The switch also performs the following judgment:
• If the port on which it the switch received the MLD query is a dynamic router port in its router port
list, the switch resets the aging timer for this dynamic router port.
• If the port is not included in its router port list, the switch adds it into its router port list as a dynamic
router port and sets an aging timer for it.
Membership reports
A host sends an MLD report to the MLD querier in the following circumstances:
• If the host has been a member of an IPv6 multicast group, after receiving an MLD query, the host
responds with an MLD report.
• If the host wants to join an IPv6 multicast group, the host sends an MLD report to the MLD querier
to announce that it is interested in the multicast information addressed to that IPv6 multicast group.
After receiving an MLD report, the switch forwards it through all the router ports in the VLAN, resolves the
address of the reported IPv6 multicast group. The switch also performs the following judgment:
• If no forwarding table entry exists for the reported IPv6 multicast group, the switch creates an entry,
adds the port as a dynamic member port to the outgoing port list, and starts a member port aging
timer for that port.
• If a forwarding table entry exists for the reported IPv6 multicast group, but the port is not included
in the outgoing port list for that group, the switch adds the port as a dynamic member port to the
outgoing port list, and starts a member port aging timer for that port.