Chapter 32 IPv6 Configuration DGS-3610 Series Configuration Guide
prefix
IPv6 Unicast or Anycast Address
Interface ID
FF02 0 1 FF Lower 24
Multicast address of the
corresponding requested node
24bits
32.1.2.3 Anycast Addresses
The anycast address is similar with the multicast address as more than one node shares an
anycast address. The difference is that only one node expects to receive the data packet of
the anycast address, while all nodes of the multicast address members expect to receive all
packets sending to this address. The anycast address is assigned to normal IPv6 unicast
address space, so the anycast address cannot be differentiated from the unicast address
from the style. For this reason, each member of all anycast addresses has to be configured
explicitly to identify the anycast address.
The anycast address can only be assigned to the devie, but cannot be
assigned to the host. Furthermore, the anycast address cannot be taken
as the source address of the message.
The RFC2373 predefines an anycast address, referred to as the anycast address of the
subnet router. The following diagram shows the anycast address format of the subnet router,
which consists of the subnet prefix followed by a series of 0 (as the interface identifier).
Where, the subnet prefix identifies a specified link (subnet) and the message to be sent to
the anycast address of the subnet router will be distributed to a router of this subnet. The
anycast address of the subnet router is usually used to some node which needs to
communicate with one router of the remote subnet.
Figure 32-2
Anycast Address Format of Subnet Router
N bits
128-n bits
Subnet Prefix
0000..0000
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