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Aging timers for dynamic ports in MLD snooping
Table 32
Aging timers for dynamic ports in MLD snooping and related messages and actions
Timer Description
Message before
expiration
Action after expiration
Dynamic router
port aging timer
When a port receives an MLD
general query with the source
address other than 0::0 or IPv6
PIM hello, the switch starts or
resets an aging timer for the
port. When the timer expires,
the dynamic router port ages
out.
MLD general query with
the source address other
than 0::0 or IPv6 PIM
hello.
The switch removes this
port from its router port
list.
Dynamic member
port aging timer
When a port dynamically joins
a multicast group, the switch
starts or resets an aging timer
for the port. When the timer
expires, the dynamic member
port ages out.
MLD report message.
The switch removes this
port from the MLD
snooping forwarding
table.
NOTE:
In MLD snooping, only dynamic ports age out. Static ports never age out.
How MLD snooping works
An MLD snooping-enabled switch performs different actions when it receives different MLD messages.
The ports in this section are dynamic ports. For information about how to configure and remove static
ports, see "
When receiving a general query
The MLD querier periodically sends MLD general queries to all hosts and routers (FF02::1) on the local
subnet to determine whether any active IPv6 multicast group members exist on the subnet.
After receiving an MLD general query, the switch forwards it to all ports in the VLAN, except the port that
received the query. The switch also performs one of the following actions:
•
If the port that received the query is a dynamic router port in the router port list, restarts the aging
timer for the port.
•
If the port that received the query is not in the router port list, adds it into the router port list as a
dynamic router port and starts an aging timer for the port.
When receiving a membership report
A host sends an MLD report to the MLD querier for the following purposes:
•
Responds to queries if the host is an IPv6 multicast group member.
•
Applies for joining an IPv6 multicast group to join.
After 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 judgment:
