Basic concepts in MLD snooping
MLD snooping related ports
As shown in Figure 21, Router A connects to the multicast source, MLD snooping runs on Switch A and Switch B, Host A and Host C are receiver hosts—namely, IPv6 multicast group members.
Figure 21: MLD snooping related ports
Ports involved in MLD snooping, as shown in Figure 21, are described as follows:
Router port—A router port is a port on the Ethernet switch that leads the switch toward the Layer-3 multicast device—DR or MLD querier. In the figure, GigabitEthernet 1/0/1 of Switch A and GigabitEthernet 1/0/1 of Switch B are router ports. The switch registers all its local 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 toward multicast group members. In the figure, GigabitEthernet 1/0/2 and GigabitEthernet 1/0/3 of Switch A and GigabitEthernet 1/0/2 of Switch B are member ports. The switch registers all the member ports on the local switch in its MLD snooping forwarding table.
![[NOTE: ]](images/note.png) | NOTE: In this document, a router port is a router-connecting port on the switch, rather than a port on a router. Unless otherwise specified, router ports and member ports in this document include static and dynamic ports. 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 dynamic router ports. | |
Aging timers for dynamic ports in MLD snooping
Table 8: Aging timers for dynamic ports in MLD snooping and related messages and actions
Timer | Description | Message before expiry | Action after expiry |
|---|---|---|---|
Dynamic router port aging timer | For each dynamic router port, the switch sets a timer initialized to the dynamic router port aging time. | 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. |
Dynamic member port aging timer | When a port dynamically joins an IPv6 multicast group, the switch sets a timer for the port, which is initialized to the dynamic member port aging time. | MLD report message. | The switch removes this port from the MLD snooping forwarding table. |
| NOTE: The port aging mechanism of MLD snooping works only for dynamic ports; a static port will never age out. | |