Ipv6 Address Types - IBM RackSwitch G8000 Application Manual

IPv6 Address Types

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RackSwitch G8000: Application Guide
IPv6 supports three types of addresses: unicast (one-to-one), multicast
(one-to-many), and anycast (one-to-nearest). Multicast addresses replace the use
of broadcast addresses.
Unicast Address
Unicast is a communication between a single host and a single receiver. Packets
sent to a unicast address are delivered to the interface identified by that address.
IPv6 defines the following types of unicast address:
• Global Unicast address: An address that can be reached and identified globally.
Global Unicast addresses use the high-order bit range up to FF00, therefore all
non-multicast and non-link-local addresses are considered to be global unicast.
A manually configured IPv6 address must be fully specified. Autoconfigured IPv6
addresses are comprised of a prefix combined with the 64-bit EUI. RFC 4291
defines the IPv6 addressing architecture.
The interface ID must be unique within the same subnet.
• Link-local unicast address: An address used to communicate with a neighbor on
the same link. Link-local addresses use the format FE80::EUI
Link-local addresses are designed to be used for addressing on a single link for
purposes such as automatic address configuration, neighbor discovery, or when
no routers are present.
Routers must not forward any packets with link-local source or destination
addresses to other links.
Multicast
Multicast is communication between a single host and multiple receivers. Packets
are sent to all interfaces identified by that address. An interface may belong to any
number of multicast groups.
A multicast address (FF00 - FFFF) is an identifier for a group interface. The
multicast address most often encountered is a solicited-node multicast address
using prefix FF02::1:FF00:0000/104 with the low-order 24 bits of the unicast or
anycast address.
The following well-known multicast addresses are pre-defined. The group IDs
defined in this section are defined for explicit scope values, as follows:
FF00:::::::0 through FF0F:::::::0
Anycast
Packets sent to an anycast address or list of addresses are delivered to the nearest
interface identified by that address. Anycast is a communication between a single
sender and a list of addresses.
Anycast addresses are allocated from the unicast address space, using any of the
defined unicast address formats. Thus, anycast addresses are syntactically
indistinguishable from unicast addresses. When a unicast address is assigned to
more than one interface, thus turning it into an anycast address, the nodes to which
the address is assigned must be explicitly configured to know that it is an anycast
address.