Introduction to MLD snooping
By analyzing received MLD messages, a Layer 2 switch that is running MLD snooping establishes mappings between ports and multicast MAC addresses and forwards IPv6 multicast data based on these mappings.
As shown in Figure 20, when MLD snooping is not running, IPv6 multicast packets are broadcast to all devices at Layer 2. When MLD snooping runs, multicast packets for known IPv6 multicast groups are multicast to the receivers at Layer 2.
Figure 20: Before and after MLD snooping is enabled on the Layer 2 switch
MLD snooping forwards multicast data to only the receivers that require it at Layer 2. It brings the following advantages:
Reducing Layer 2 broadcast packets, thus saving network bandwidth.
Enhancing the security of multicast traffic.
Facilitating the implementation of per-host accounting.