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Chapter 37 IPv6 Multicast Protocol 
37.1 MLD Snooping 
37.1.1 Introduction to MLD Snooping 
MLD,  the  Multicast  Listener  Discovery  Protocol,  is  used  to  realize  multicasting  in  the  IPv6. 
MLD is used by the network equipments such as routers which supports multicast for multicast 
listener  discovery,  also  used  by  listeners  looking  forward  to  join  certain  multicast  group 
informing the router to receive data packets from certain multicast address, all of which are 
done through MLD message exchange. First the router send an MLD Multicast listener Query 
message  through  a  multicast  address  which  can  address  all  the  listeners  (namely  ff02::1). 
Once there is a listener who wishes to join the multicast address, it will send a MLD Multicast 
listener Report back through the multicast address. 
MLD  Snooping  is  namely  the  MLD  listening.  The  switch  restricts  the  multicast  traffic  from 
flooding  through  MLD Snooping,  and forward  the  multicast  traffic  to  ports  associated  to 
multicast devices only. The switch listens to the MLD messages between multicast routers and 
listeners, and maintains the multicast group forwarding list based on the listening result. The 
switches forwards multicast packets according to the multicast forwarding list 
The switch realizes the MLD Snooping function while supporting MLD v2. This way, the user 
can acquire IPv6 multicast with the switch. 
37.1.2 MLD Snooping Configuration Task 
1.  Enable the MLD Snooping function 
2.  Configure the MLD Snooping 
1.  Enable the MLD Snooping function 
Command 
Explanation 
Global Mode 
ipv6 mld snooping 
no ipv6 mld snooping 
Enable  global  MLD  Snooping,  the  “no  ipv6 
mld snooping” command disables the global 
MLD snooping. 
2. Configure MLD Snooping 
Command 
Explanation 
Global Mode 
ipv6 mld snooping vlan <vlan-id> 
no ipv6 mld snooping vlan <vlan-id> 
Enable MLD Snooping on specific VLAN. The “no” 
form of this command disables MLD Snooping on 










