As with IPv4 addresses, you can assign multiple
IPv6 addresses to a switch interface. IPv6 Address Types presents the three major types of IPv6
addresses that you can assign to a switch interface.
A major difference between IPv4 and IPv6 addresses is that IPv6 addresses support
scope , which describes the topology in which the address may be used as a unique
identifier for an interface or set of interfaces.
Unicast and multicast addresses support scoping
in the following ways:
Unicast addresses support two types of scope:
global scope and local scope. In turn, local scope supports site-local addresses
and
link-local addresses. IPv6 Address Types describes global, site-local, and
link-local addresses and the topologies in which they are used.
Multicast addresses support a scope field,
which IPv6 Address Types describes.
IPv6 Address Types
Address Type
Description
Address Structure
Unicast
An address for a single interface. A packet sent to a unicast address is delivered
to the interface identified by the address.
Depends on the type of the unicast address:
Aggregatable global address: An address
equivalent to a global or public IPv4 address. The address
structure is as follows: a fixed prefix of 2000::/3 (001), a
45-bit global routing prefix, a 16-bit subnet ID, and a 64-bit
interface ID.
Site-local address: An address used within
a site or intranet. (This address is similar to a private IPv4
address.) A site consists of multiple network links. The address
structure is as follows: a fixed prefix of FEC0::/10 (1111 1110
11), a 16-bit subnet ID, and a 64-bit interface ID.
Link-local address: An address used
between directly connected nodes on a single network link. The
address structure is as follows: a fixed prefix of FE80::/10
(1111 1110 10) and a 64-bit interface ID.
IPv4-compatible address: An address used
in IPv6 transition mechanisms that tunnel IPv6 packets
dynamically over IPv4 infrastructures. The address embeds an
IPv4 address in the low-order 32 bits and the high-order 96 bits
are zeros. The address structure is as follows:
0:0:0:0:0:0:A.B.C.D.
Loopback address: An address
(0:0:0:0:0:0:0:1 or ::1) that a switch can use to send an IPv6
packet to itself. You cannot assign a loopback address to a
physical interface.
Unspecified address: An address
(0:0:0:0:0:0:0:0 or ::) that a node can use until you configure
an IPv6 address for it.
Multicast
An address for a set of interfaces belonging to different nodes. Sending a packet
to a multicast address results in the delivery of the packet to all interfaces in
the set.
A multicast address has a fixed prefix of FF00::/8 (1111 1111). The next 4 bits define
the address as a permanent or temporary address. The next 4 bits define the scope
of the address (node, link, site, organization, global).
Anycast
An address for a set of interfaces belonging to different nodes. Sending a packet
to an anycast address results in the delivery of the packet to the closest interface
identified by the address.
An anycast address looks similar to a unicast address, because it is allocated from
the unicast address space. If you assign a unicast address to multiple interfaces,
it is an anycast address. An interface assigned an anycast address must be configured
to recognize the address as an anycast address.
An anycast address can be assigned to a switch only.
An anycast address must not be used as the source address of an IPv6 packet.
A switch automatically configures a link-local unicast address for an interface by
using the prefix of FE80::/10 (1111 1110 10) and a 64-bit interface ID. The 128-bit
IPv6 address is then subjected to duplicate address detection to ensure that the address
is unique on the link. If desired, you can override this automatically configured
address by explicitly configuring an address.
Note: RUCKUS ICX devices
support RFC 2526, which requires that within each subnet, the highest 128 interface
identifier values reserved for assignment as subnet anycast addresses. Thus, if
you
assign individual IPv6 addresses within a subnet, the second highest IPv6 address
in the
subnet does not work.