386
Configuring MLD snooping
Hardware compatibility
•
MLD snooping is available only on the MSR series routers with fixed Layer 2 switching interfaces or
Layer 2 switching interface modules.
•
The MSR-900 and MSR20-1 routers do not support MLD snooping.
Overview
MLD snooping is an IPv6 multicast constraining mechanism that runs on Layer 2 devices to manage and
control IPv6 multicast groups.
By analyzing received MLD messages, an MLD snooping-enabled Layer 2 device establishes mappings
between ports and multicast MAC addresses and forwards IPv6 multicast data based on these
mappings.
As shown in
, without MLD snooping, a Layer 2 switch floods IPv6 multicast packets out of all
ports but the incoming port. MLD snooping enables a Layer 2 switch to forward IPv6 multicast packets
destined for a known IPv6 multicast group address out of only ports that have multicast receivers. This
feature improves bandwidth efficiency, enhances multicast security, and helps per-host accounting for
multicast users.
Figure 103
Before and after MLD snooping is enabled on the Layer 2 device