Reference Guide

Multicast Support 371
MLD Snooping
Hosts use the MLD protocol to report their participation in Multicast
sessions, and the device uses MLD snooping to build Multicast membership
lists. It uses these lists to forward Multicast packets only to device ports where
there are host nodes that are members of the Multicast groups. The device
does not support MLD Querier.
Hosts use the MLD protocol to report their participation in Multicast
sessions.
The device supports two versions of MLD snooping:
• MLDv1 snooping detects MLDv1 control packets, and sets up traffic
bridging, based on IPv6 destination Multicast addresses.
• MLDv2 snooping uses MLDv2 control packets to forward traffic based on
the source IPv6 address, and the destination IPv6 Multicast address.
The actual MLD version is selected by the Multicast router in the network.
In an approach similar to IGMP snooping, MLD frames are snooped as they
are forwarded by the device from stations to an upstream Multicast router
and vice versa. This facility enables a device to conclude the following:
• On which ports stations interested in joining a specific Multicast group are
located
• On which ports Multicast routers sending Multicast frames are located
This knowledge is used to exclude irrelevant ports (ports on which no stations
have registered to receive a specific Multicast group) from the forwarding set
of an incoming Multicast frame.
If you enable MLD snooping in addition to the manually-configured
Multicast groups, the result is a union of the Multicast groups and port
memberships derived from the manual setup and the dynamic discovery by
MLD snooping. Only static definitions are preserved when the system is
rebooted.
Global Parameters
To enable Multicast filtering and IGMP Snooping:
1
Click Switching > Multicast Support > Global Parameters in the tree
view to display the
Global Parameters page.