MLD Snooping Overview 581
switch registers all its local router ports (including static and dynamic router
ports) in its router port list.
■ Member port: A member port (also known as IPv6 multicast group member
port) is a port on the Ethernet switch that leads switch towards multicast group
members. In the figure, Ethernet 1/0/2 and Ethernet 1/0/3 of Switch A and
Ethernet 1/0/2 of Switch B are member ports. The switch registers all the
member ports (including static and dynamic member ports) on the local device
in its MLD Snooping forwarding table.
n
■ Whenever mentioned in this document, a router port is a router-connecting
port on the switch, rather than a port on a router.
■ On an MLD-snooping-enabled switch, the ports that received MLD general
queries with the source address other than 0::0 or IPv6 PIM hello messages are
router ports.
Aging timers for dynamic ports in MLD Snooping
n
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 running MLD Snooping performs different actions when it receives
different MLD messages, as follows:
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.
Table 56 Aging timers for dynamic ports in MLD Snooping and related messages and
actions
Timer Description
Message before
expiry Action after expiry
Router port aging
timer
For each router port,
the switch sets a timer
initialized to the aging
time of the route port.
MLD general query of
which the source
address is not 0::0 or
IPv6 PIM hello.
The switch removes
this port from its
router port list.
Member port aging
timer
When a port joins an
IPv6 multicast group,
the switch sets a timer
for the port, which is
initialized to the
member port aging
time.
MLD report message. The switch removes
this port from the IPv6
multicast group
forwarding table.
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