Specifications

72 Implementing IBM System Networking 10Gb Ethernet Switches
Most IBM Networking OS features permit IP addresses to be configured using either IPv4 or
IPv6 address formats. Throughout this manual, IP address is used in places where either an
IPv4 or IPv6 address is allowed. In places where only one type of address is allowed, the type
(IPv4 or IPv6) is specified.
2.5.2 IPv6 address types
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 addresses
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 addresses:
򐂰 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. Auto-configured IPv6 addresses are composed of a prefix
combined with the 64-bit EUI. RFC 4291 (found at
http://www.ietf.org/rfc/rfc4291.txt) 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 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.
򐂰 Unique Local IPv6 Unicast addressees are synonymous to private addresses in IPv4 and
are in the FC00::/7 range.
Multicast addresses
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 predefined. 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.