HP 6200YL - Manual (Page 64)

IPv6 Addressing
Multicast Application to IPv6 Addressing
tions, router advertisements, and responses to DAD messages. It also avoids
the bandwidth consumption used for broadcasts by narrowing the scope of
possibly interested destinations for various types of messages.
Overview of the Multicast Operation in IPv6
When IPv6 is enabled on a VLAN interface on the switch, the interface
automatically joins the All-Nodes and Solicited-Node multicast address
groups for each of its configured unicast addresses. The interface also
attempts to learn of other devices by sending solicitations to additional, well-
known multicast groups, such as the following:
■ all routers
■ all MLDv2-capable routers, if multicast listener discovery (MLD) is
enabled on the interface
■ all DHCP agents (if DHCP is enabled on the interface)
There is a separate, solicited node multicast group for each IPv6 unicast
address configured on a given interface. These automatically generated
groups are limited in scope to the VLANs on which the node resides. Where
multiple IPv6 unicast addresses on the same node differ only in their prefixes,
they join the same solicited-node multicast group. Solicited-Node multicast
groups are used, for example, in Autoconfiguration. In this case, a node
attempting to Autoconfigure a link-local address computes the solicited-node
multicast address for the proposed link-local address, then sends a Neighbor
solicitation to this solicited-node multicast address. If there is no response
from another node, the proposed address is available for use.
For more on Neighbor Discovery, refer to “Neighbor Discovery (ND)” on
page 4-16.
For information on Multicast Listener Discovery (MLD) refer to the chapter
titled “Multicast Listener Discovery (MLD) Snooping”.
When MLD is enabled on an interface, you can use show ipv6 mld [ vlan < vid >]
to list the active multicast group activity the switch has detected per interface
from other devices.
IPv6 Multicast Address Format
The multicast address format has three principal sections in the leading 16
bits:
■ identifier: ff (bits 1-8)
■ flags: 0xxx (bits 9-12)
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