HP A5500 SI Switch Series Configuration Manual page 255

If no forwarding table entry exists for the reported IPv6 multicast group, the switch creates an entry,
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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
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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.
If a forwarding table entry exists for the reported IPv6 multicast group and the port is included in
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the outgoing port list, which means that this port is already a dynamic member port, the switch
resets the member port aging timer for that port.
NOTE:
A switch does not forward an MLD report through a non-router port. The reason is that if the switch
forwards a report message through a member port, all the attached hosts that monitor the reported
IPv6 multicast address suppress their own reports after receiving this report according to the MLD
report suppression mechanism. This prevents the switch from determining whether the reported
multicast group still has active members attached to that port.
For more information about the MLD report suppression mechanism, see the chapter "MLD
configuration."
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 determines
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
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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
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the MLD done message to all router ports in the native VLAN. Because the switch has not
determined whether any other hosts attached to the port are still monitoring 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.
After 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. After 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. The switch also performs the following judgment on the port that
received the MLD done message:
If the port (a dynamic member port supposed) receives any MLD report in response to the MLD
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multicast-address-specific query before its aging timer expires, it indicates that a host attached to
the port is receiving or expecting to receive IPv6 multicast data destined for that IPv6 multicast
group. The switch resets the aging timer for the port.
If the port does not receive an MLD report in response to the MLD multicast-address-specific query
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before its aging timer expires, it indicates that no hosts attached to the port are still monitoring that
IPv6 multicast group address. The switch removes the port from the outgoing port list of the
forwarding table entry for that IPv6 multicast group when the aging timer expires.
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