How Mld Snooping Works - H3C S5500-EI Series Operation Manual

Operation Manual – Multicast
H3C S5500-EI Series Ethernet Switches
Note:
The port aging mechanism of MLD Snooping works only for dynamic ports; a static port
will never age out.

3.1.3 How MLD Snooping Works

A switch running MLD Snooping performs different actions when it receives different
MLD messages, as follows:
I. General queries
The MLD querier periodically sends MLD general queries to all hosts and routers
(FF02::1) on the local subnet to find out whether IPv6 multicast group members exist on
the subnet.
Upon receiving an MLD general query, the switch forwards it through all ports in the
VLAN except the receiving port and performs the following to the receiving port:
If the receiving port is a router port existing in its router port list, the switch resets
the aging timer of this router port.
If the receiving port is not a router port existing in its router port list, the switch adds
it into its router port list and sets an aging timer for this router port.
II. Membership reports
A host sends an MLD report to the multicast router in the following circumstances:
Upon receiving an MLD query, an IPv6 multicast group member host responds
with an MLD report.
When intended to join an IPv6 multicast group, a host sends an MLD report to the
multicast router to announce that it is interested in the multicast information
addressed to that IPv6 multicast group.
Upon 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, and performs the
following to the receiving port:
If no forwarding table entry exists for the reported IPv6 multicast group, the switch
creates an entry, adds the port as 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
member port to the outgoing port list, and starts a member port aging timer for that
port.
Chapter 3 MLD Snooping Configuration
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