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MLD snooping configuration
MLD snooping overview
MLD snooping is an IPv6 multicast constraining mechanism that runs on Layer 2 switches to manage and
control IPv6 multicast groups.
Introduction to MLD snooping
By analyzing received MLD messages, a Layer 2 switch that runs MLD snooping establishes mappings
between ports and multicast MAC addresses and forwards IPv6 multicast data based on these
mappings.
As shown in Figure 63, when MLD sn
ooping 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 63 Before and after MLD snooping is enabled on the Layer 2 switch
IPv6 multicast packet transmission
without MLD Snooping
Source
Multicast router
Host A
Receiver
Host B
Host C
Receiver
IPv6 multicast packets
Layer 2 switch
IPv6 multicast packet transmission
when MLD Snooping runs
Source
Multicast router
Host A
Receiver
Host B
Host C
Receiver
Layer 2 switch
MLD snooping forwards multicast data to only the receivers that require it at Layer 2. It has 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
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