Allied Telesis AlliedWare Plus Operating System Version 5.4.4C (x310-26FT,x310-26FP,x310-50FT,x310-50FP) - Manual (Page 787)

MLD and MLD Snooping Introduction and Commands
Software Reference for x310 Series Switches
C613-50046-01 REV A AlliedWare Plus TM Operating System - Version 5.4.4C 32.3
MLD Snooping
MLD Snooping is a feature whereby a Layer 2 switch listens to or "snoops" the MLD
messages passing through the switch or from member hosts and multicast routers. The
purpose of MLD Snooping is to provide efficient Layer 2 multicast forwarding, by sending
only to hosts that have expressed an interest in receiving the multicast data.
Hosts express an interest in receiving multicast data for a given multicast group by
sending an MLD join message. Without MLD Snooping, if one host expresses an interest in
getting multicast data for a given group, by sending an MLD join for the multicast group,
then all hosts connected to the same VLAN will also receive the multicast data. This wastes
bandwidth on the switch ports connected to the host that are not interested in receiving
the multicast data. Snooping takes note of exactly which ports have received joins for a
given group, and send that group only to those ports.
MLD Snooping is enabled by default globally for the switch. It can be enabled and
disabled on a per-VLAN basis.
For MLD Snooping to operate, both IGMP Snooping and MLD Snooping must be enabled
globally on the switch. By default, IGMP Snooping is also enabled globally. To enable IGMP
Snooping if it has been disabled, use the
ip igmp snooping command on page 31.20 in
Global Configuration mode.
MLD Snooping makes a distinction between Member ports, which are ports connected to
members hosts, and Router ports, which are ports connected to, or directed towards, a
Layer 3 router or a Layer 3 switch.
Figure 32-1: Sample running-config showing an MLD Snooping Querier set on vlan2
Note The IPv6 Multicast addresses shown can be derived from IPv6 unicast prefixes as
per RFC 3306.The IPv6 unicast prefix reserved for documentation is 2001:0db8::/
32 as per RFC 3849. Using the base /32 prefix the IPv6 multicast prefix for
2001:0db8::/32 is ff3x:20:2001:0db8::/64. Where an RP address is 2001:0db8::1
the embedded RP multicast prefix is ff7x:120:2001:0db8::/96. For ASM (Any-
Source Multicast) the IPV6 multicast addresses allocated for documentation
purposes are ff0x::0db8:0:0/96 as per RFC 6676. This is a /96 prefix so that it can
be used with group IDs as per RFC 3307. These addresses should not be used for
practical networks (other than for testing purposes), nor should they appear in
any public network.
!
ipv6 mld snooping
!
interface vlan2
ipv6 mld snooping querier
!