H3C S9500 Series Operation Manual page 7

Operation Manual – MLD Snooping
H3C S9500 Series Routing Switches
If no forwarding table entry exists for the reported group, the switch creates an
entry, adds the port as a dynamic member port into the outgoing port list, and
starts a member port aging timer for that port.
If a forwarding table entry exists for the reported group, but the port is not included
in the outgoing port list for that group in the forwarding entry, the switch adds the
port as a dynamic member port into the outgoing port list, and starts an aging timer
for that port.
If a forwarding table entry exists for the reported group and the port is included in
the outgoing port list, which means that this port is already a dynamic member port
for that group, the switch resets the aging timer for that port.
Note:
A switch will not forward an MLD report through a non-router port in a VLAN.
III. Done messages
When a host leaves an IPv6 multicast group, the host sends an MLD done message to
the multicast router.
When the switch receives an MLD done message on a dynamic member port, the
switch first checks whether a forwarding table entry for the IPv6 multicast group
address in the message exists, and, if one exists, whether the outgoing port list
contains the port.
If the forwarding table entry does not exist or if the outgoing port list does not
contain the port, the switch discards the MLD done message instead of forwarding
it to any port.
If the forwarding table entry exists and the outgoing port list contains the port, the
switch forwards the MLD done message to all router ports in the native VLAN.
Because the switch does not know whether any other hosts attached to the port
are still listening to that IPv6 multicast group address, the switch does not
immediately remove the port from the outgoing port list of the forwarding table
entry for that group; instead, it resets the aging timer for the port.
Upon receiving an MLD done message from a host, the MLD querier resolves the IPv6
multicast group address in the message and sends an MLD multicast-address-specific
query to that IPv6 multicast group address through the port that received the MLD done
message. Upon receiving the MLD multicast-address-specific query, the switch
forwards it through all the router ports in the VLAN and all member ports for that IPv6
multicast group, and performs the following to the receiving port:
If any MLD report in response to the MLD multicast-address-specific query is
received on the port (suppose it is a dynamic member port) before its aging timer
Chapter 1 MLD Snooping Configuration
1-5