Chapter 3 Mld Snooping Configuration; Mld Snooping Overview; How Mld Snooping Works; Basic Concepts In Mld Snooping - H3C S3610 Series Operation Manual

Operation Manual – Multicast Protocol
H3C S3610&S5510 Series Ethernet Switches

Chapter 3 MLD Snooping Configuration

3.1 MLD Snooping Overview

Multicast Listener Discovery Snooping (MLD Snooping) is an IPv6 multicast
constraining mechanism that runs on Layer 2 devices to manage and control IPv6
multicast groups.

3.1.1 How MLD Snooping Works

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 Figure 3-1, when MLD Snooping 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.
Multicast packet transmission
Source
HostA
Receiver
Figure 3-1 IPv6 multicast before and after MLD Snooping runs

3.1.2 Basic Concepts in MLD Snooping

I. MLD Snooping related ports
As shown in Figure 3-2, Router A connects to the multicast source, MLD Snooping runs
on Switch A and Switch B, Host A and Host C are receiver hosts (namely, IPv6 multicast
group members).
without MLD Snooping
Multicast
Router
Layer 2 Ethernet
Switch
HostC
Receiver
HostB
IPv6 Multicast Packets
Chapter 3 MLD Snooping Configuration
Multicast packet transmission
when MLD Snooping runs
Source
HostA
Receiver
HostB
3-1
Multicast
Router
Layer 2 Ethernet
Switch
HostC
Receiver