Configuring Multicast Forwarding
MLD Snooping
Cisco Small Business 300 Series Managed Switch Administration Guide 158
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• IGMP Querier Version—Select the IGMP version used if the switch
becomes the elected querier. Select IGMPv3 if there are switches and/or
multicast routers in the VLAN that perform source-specific IP multicast
forwarding.
STEP 5 Click Apply. The switch is updated.
MLD Snooping
To support selective multicast forwarding (IPv6), Bridge Multicast filtering must be
enabled, and MLD Snooping must be enabled globally and for each relevant
VLAN.
NOTE The switch supports MLD Snooping only on static VLANs. It does not support MLD
Snooping on dynamic VLANs
The switch uses this feature to build Multicast membership lists. It uses the lists to
forward Multicast packets only to switch ports where there are host nodes that are
members of the Multicast groups. The switch does not support MLD Querier.
Hosts use the MLD protocol to report their participation in Multicast sessions.
The switch 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 switch from stations to an upstream Multicast router and vice
versa. This facility enables a switch 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.
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