Configuring MLD snooping
Overview
Multicast Listener Discovery (MLD) snooping is a multicast constraining mechanism that runs on Layer 2
devices to manage and control IPv6 multicast groups.
By analyzing received MLD messages, a Layer 2 device running MLD snooping establishes mappings
between ports and multicast MAC addresses and forwards IPv6 multicast data based on these
mappings.
As shown in
to all devices at Layer 2. When MLD snooping is running on the switch, IPv6 multicast packets for known
multicast groups are multicast to the receivers, rather than flooded to all hosts at Layer 2.
Figure 252 IPv6 multicast forwarding before and after MLD snooping runs
MLD snooping enables the Layer 2 switch to forward IPv6 multicast data only to the receivers that require
the data at Layer 2. It has the following advantages:
Reducing Layer 2 broadcast packets and saving network bandwidth
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Enhancing the security of IPv6 multicast traffic
Facilitating the implementation of per-host accounting
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Basic concepts in MLD snooping
MLD snooping related ports
As shown in
Switch B, Host A and Host C are receiver hosts (IPv6 multicast group members).
Figure
252, when MLD snooping is not running on the switch, multicast packets are flooded
Figure
253, Router A connects to the multicast source, MLD snooping runs on Switch A and
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