Licensing Requirements and Limitations for MLD Snooping

Involved Network Elements

An IPv6 multicast network consists of the following network elements:

Multicast source

A device that sends multicast data to receiver hosts. For example, a video server is a multicast source.
IPv6 Protocol Independent Multicast (PIM) device

A device that uses the IPv6 PIM protocol to generate and maintain multicast routing entries and forwards multicast data based on multicast routing entries. On an IPv6 multicast network, all Layer 3 devices must run IPv6 PIM; otherwise, multicast forwarding paths cannot be established.
MLD querier

A device that exchanges MLD messages with receiver hosts to create and maintain group memberships. On a multicast network, Layer 3 devices connected to network segments of receivers must run the MLD protocol or be configured with static MLD groups. Otherwise, upstream PIM devices cannot know the multicast groups that users want to join, and therefore cannot establish multicast forwarding paths.
MLD snooping device

A device that listens to MLD messages exchanged between upstream Layer 3 multicast devices and receiver hosts to create and maintain Layer 2 multicast forwarding entries, which are used for accurate multicast data forwarding on a Layer 2 network. To prevent broadcasting of multicast packets on a Layer 2 network and conserve network bandwidth, it is recommended that you configure MLD snooping on Layer 2 devices.
Receiver

A multicast user that receives multicast data. A receiver can be a PC, a set top box, or any device with multicast client installed.

The "MLD Snooping Configuration" chapter describes how to configure MLD snooping on a Layer 2 device.

Licensing Requirements

MLD snooping is a basic feature of a switch and is not under license control.

Feature Support in V200R019C10

All models of S2720, S5700, and S6700 series switches support MLD Snooping.

For details about software mappings, visit Hardware Query Tool and search for the desired product model.

Feature Limitations

All the MLD snooping configurations on interfaces mentioned in this chapter are performed on Layer 2 physical interfaces, including Eth-Trunk interfaces.
For the S5735-L, S5735S-L, S5735S-L-M, S5735-S, S5735-S-I, and S5735S-S, the multicast functions (both Layer 2 and Layer 3 multicast functions) conflict with the flow control function.
If both Layer 2 and Layer 3 multicast services are required in a VLAN, enable MLD and IPv6 PIM on the corresponding VLANIF interface first, and then enable MLD Snooping in the VLAN. If MLD Snooping is enabled in the VLAN first, MLD and IPv6 PIM cannot be enabled on the VLANIF interface.
On a switch running MLD snooping, multicast flows that are not requested by users are considered unknown multicast flows. Multicast flows are considered unknown if they do not match any entry in the multicast forwarding table or if they match multicast forwarding entries with an empty outbound interface list. These flows are not requested by users. The switch broadcasts unknown IPv6 multicast flows in the corresponding VLAN.
To prevent broadcast of unknown multicast flows, run the multicast drop-unknown command in a VLAN or run the unknown-frame multicast drop command in a VSI to configure a switch to drop unknown multicast flows.

For the S5735-L, S5735S-L, S5735S-L-M, S5735-S, S5735-S-I, and S5735S-S, if MAC address-based forwarding is configured as the Layer 2 multicast forwarding mode and the multicast drop-unknown command is executed, unknown multicast packets destined for the following reserved network segments and IP address cannot be dropped: 239.0.0.0/8, 224.0.0.0/24, 224.0.1.0/24, FF0X:0:0:0:0:0:0:0/96, FF0X::DB8:0:0/96, and the IPv6 address with the last 32 bits being 0000:00XX. To drop such unknown multicast packets, configure a traffic policy.