H3C Technologies H3C S12500 Series Switches - Manual (Page 300)

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Configuring MLD snooping
Overview
MLD snooping runs on a Layer 2 switch as an IPv6 multicast constraining mechanism to improve multicast
forwarding efficiency. It creates Layer 2 multicast forwarding entries from MLD messages that are
exchanged between the hosts and the router.
As shown in
Figure 78 , when MLD snooping is not enabled, the Layer 2 switch floods IPv6 multicast
packets to all hosts. When MLD snooping is enabled, the Layer 2 switch forwards multicast packets of
known IPv6 multicast groups to only the receivers.
The term "router" in this document refers to both routers and Layer 3 switches.
Figure 78 Before and after MLD snooping is enabled on the Layer 2 device
MLD snooping enables the Layer 2 switch to forward IPv6 multicast data to only the receivers that require
the data 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
Basic MLD snooping concepts
MLD snooping related ports
As shown in Figure 79 , MLD snooping runs on Switch A and Switch B, Host A and Host C are receivers
in an IPv6 multicast group.