H3C Technologies H3C S10500 Series Switches - Manual (Page 341)

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MLD configuration
NOTE:
•
The term router in this document refers to both routers and Layer 3 switches.
• The term interface in the MLD features refers to Layer 3 interfaces, including VLAN interfaces and
route-mode (or Layer 3) Ethernet ports. You can set an Ethernet port to operate in route mode by using
the port link-mode route command (see Layer 2—LAN Switching Configuration Guide).
MLD overview
An IPv6 router uses the Multicast Listener Discovery (MLD) protocol to discover the presence of multicast
listeners on the directly attached subnets. Multicast listeners are nodes that want to receive IPv6 multicast
packets.
Through MLD, the router can determine whether any IPv6 multicast listeners exist on the directly
connected subnets, put corresponding records in the database, and maintain timers related to IPv6
multicast addresses.
Routers running MLD use an IPv6 unicast link-local address as the source address to send MLD messages.
MLD messages are Internet Control Message Protocol for IPv6 (ICMPv6) messages. All MLD messages
are confined to the local subnet, with a hop count of 1.
MLD versions
• MLDv1 (defined in RFC 2710), which is derived from IGMPv2.
• MLDv2 (defined in RFC 3810), which is derived from IGMPv3.
All MLD versions support the Any-Source Multicast (ASM) model. In addition, MLDv2 can directly
implement the Source-Specific Multicast (SSM) model, but MLDv1 must work with the MLD SSM mapping
function to implement SSM service.
NOTE:
For more information about the ASM and SSM models, see the chapter “Multicast overview.”
How MLDv1 works
MLDv1 implements IPv6 multicast listener management based on the query/response mechanism.
MLD querier election
All IPv6 multicast routers routers on the same subnet can monitor MLD listener report messages (often
called “reports”) from hosts, but only one router is needed for sending MLD query messages (often called
“queries”). A querier election mechanism determines which router will act as the MLD querier on the
subnet.