Basic MLD snooping concepts

As shown in Figure 43, MLD snooping runs on Switch A and Switch B, and Host A and Host C are receiver hosts in an IPv6 multicast group.

The following describes the ports involved in MLD snooping, as shown in Figure 43:

• Router port—Layer 3 multicast device-side port. Layer 3 multicast devices include designated routers and MLD queriers. In Figure 43, FortyGigE 1/0/1 of Switch A and FortyGigE 1/0/1 of Switch B are the router ports. A switch records all its local router ports in a router port list.

  Do not confuse the "router port" in MLD snooping with the "routed interface" commonly known as the "Layer 3 interface." The router port in MLD snooping is a Layer 2 interface.

• Member port—Multicast receiver-side port. In Figure 43, FortyGigE 1/0/2 and FortyGigE 1/0/3 of Switch A and FortyGigE 1/0/2 of Switch B are member ports. A switch records all its local member ports in its MLD snooping forwarding table.

  Unless otherwise specified, router ports and member ports in this document include both static and dynamic router ports and member ports.

	NOTE: When MLD snooping is enabled, all ports that receive IPv6 PIM hello messages or MLD general queries with a source IP address other than 0::0 are considered dynamic router ports.

The following are aging timers for dynamic ports in MLD snooping:

• Dynamic router port aging timer—The switch starts this timer for a port that receives an MLD general query with the source address other than 0::0 or an IPv6 PIM hello message. If the port does not either of receive these messages before the timer expires, the switch removes the port from its router port list.

• Dynamic member port aging timer—The switch starts this timer for a port that receives an MLD report. If the port does not receive a report before the timer expires, the switch removes the port from the MLD snooping forwarding entries.

	NOTE: In MLD snooping, only dynamic ports age out. Static ports never age out.