Processing Of Ipv6 Multicast Protocol Messages; Protocols And Standards - 3Com S7906E Configuration Manual

MLD message
Report
Done

Processing of IPv6 Multicast Protocol Messages

With Layer 3 multicast routing enabled, an MLD snooping switch processes IPv6 multicast protocol
messages differently under different conditions, specifically as follows:
1) If only MLD is enabled, or both MLD and IPv6 PIM are enabled on the switch, the switch handles
IPv6 multicast protocol messages in the normal way.
2) In only IPv6 PIM is enabled on the switch:
The switch broadcasts MLD messages as unknown messages in the VLAN.
Upon receiving an IPv6 PIM hello message, the switch will maintain the corresponding dynamic
router port.
3) When MLD is disabled on the switch:
If IPv6 PIM is disabled, the switch deletes all its dynamic member ports and dynamic router ports.
If IPv6 PIM is enabled, the switch deletes only its dynamic member ports without deleting its
dynamic router ports.
On a switch with Layer-3 IPv6 multicast routing enabled, use the display mld group port-info
command to view Layer-2 port information.
For details about the display mld group port-info command, refer to MLD Commands in the IP
Multicast Volume.
4) When IPv6 PIM is disabled on the switch:
If MLD is disabled, the switch deletes all its dynamic router ports.
If MLD is enabled, the switch maintains all its dynamic member ports and dynamic router ports.

Protocols and Standards

MLD snooping is documented in:
RFC 4541: Considerations for Internet Group Management Protocol (IGMP) and Multicast Listener
Discovery (MLD) Snooping Switches
When receiving a report for an IPv6 multicast group, the proxy looks up the
multicast forwarding table for the entry for the multicast group. If the forwarding
entry is found with the receiving port contained as a dynamic port in the outgoing
port list, the proxy resets the aging timer for the entry. If the forwarding entry is
found but the outgoing port list does not include the receiving port, the proxy adds
the port to the outgoing port list as a dynamic member port and starts an aging
timer for it. If no forwarding entry is found, the proxy creates the entry, adds the
receiving port to the outgoing port list as a dynamic member port and starts an
aging timer for the port, and then, sends a report to the group out all router ports.
In response to a done message for an IPv6 multicast group, the proxy sends a
multicast-address-specific query for the group out the receiving port. After making
sure that no member port is contained in the forwarding entry for the IPv6 multicast
group, the proxy sends a done message for the group out all router ports.
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