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Copyright © 2010, Juniper Networks, Inc.
NOTE: You can use two colons (::) only once in an IPv6 address to represent
hexadecimal fields of consecutive zeros.
IPv6 Address Prefix
An IPv6 address prefix is a combination of an IPv6 prefix (address) and a prefix length.
The prefix takes the form ipv6-prefix/prefix-length and represents a block of address
space (or a network). The ipv6-prefix variable follows general IPv6 addressing rules (see
RFC 2373 for details). The /prefix-length variable is a decimal value that indicates the
number of contiguous, higher-order bits of the address that make up the network portion
of the address. For example, 10FA:6604:8136:6502::/64 is a possible IPv6 prefix.
Address Types
IPv6 can use several types of addresses:
Unicast—Used to identify a single interface, this release of the E Series router product
supports the following unicast address types:
Global aggregatable—Provides for aggregation of routing prefixes to limit the number
of global routing table entries
Link-local—Eliminates the need for a globally unique prefix. Local-link addresses
allow communications between devices on a local link.
Site-local—Used as private addresses to restrict communication to a domain portion.
NOTE: IPv6 routers must not forward packets that have site-local source
or destination addresses outside the site.
IPv4-compatible—Contains a standard IPv4 address in the lower-order 32 bits of
the address and zeros in the higher-order 96 bits of the address. For example, the
format of an IPv4-compatible IPv6 address is 0:0:0:0:0:0:A.B.C.D (or condensed as
::A.B.C.D). In other words, devices using IPv6 use the entire 128-bit IPv4-compatible
IPv6 address, whereas IPv4 devices use the IPv4 address embedded within the
lower-order 32-bits of the address. You would use IPv4-compatible IPv6 addresses
for devices that must support both IPv4 and IPv6 protocols.
Multicast—Used for sending packets to multiple destinations. A multicast transmission
sends packets to all interfaces that are part of a multicast group. The group is
represented by the IPv6 destination address of the packet.
Anycast – Used for a set of interfaces on different nodes. An anycast transmission
sends packets to only one of the interfaces associated with the address, not to all of
the interfaces. This interface is typically the closest interface, as defined by the routing
protocol.
Chapter 2: Configuring IPv6
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