R0106-HP MSR Router Series Layer 3 - IP Services Configuration Guide(V7)

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An IPv6 address consists of an address prefix and an interface ID, which are equivalent to the network
ID and the host ID of an IPv4 address.
An IPv6 address prefix is written in IPv6-address/prefix-length notation, where the prefix-length is a
decimal number indicating how many leftmost bits of the IPv6 address includes the address prefix.
IPv6 address types
IPv6 addresses include the following types:
• Unicast address—An identifier for a single interface, similar to an IPv4 unicast address. A packet
sent to a unicast address is delivered to the interface identified by that address.
• Multicast address—An identifier for a set of interfaces (typically belonging to different nodes),
similar to an IPv4 multicast address. A packet sent to a multicast address is delivered to all
interfaces identified by that address.
There are no broadcast addresses in IPv6. Their function is replaced by multicast addresses.
• Anycast address—An identifier for a set of interfaces (typically belonging to different nodes). A
packet sent to an anycast address is delivered to the nearest interface among the interfaces
identified by that address. The nearest interface is chosen according to the routing protocol'
measure of distance.
The type of an IPv6 address is designated by the first several bits, called the format prefix.
Table 7 Mappings between address types and format prefixes
T
yp
e Format
p
refix (binar
y
) IPv6
p
refix ID
Unicast
address
Unspecified address 00...0 (128 bits) ::/128
Loopback address 00...1 (128 bits) ::1/128
Link-local address 1111111010 FE80::/10
Global unicast address Other forms N/A
Multicast address 11111111 FF00::/8
Anycast address
Anycast addresses use the unicast address space and have the
identical structure of unicast addresses.
Unicast addresses
Unicast addresses include global unicast addresses, link-local unicast addresses, the loopback address,
and the unspecified address.
• Global unicast addresses—Equivalent to public IPv4 addresses, global unicast addresses are
provided for Internet service providers. This type of address allows for prefix aggregation to restrict
the number of global routing entries.
• Link-local addresses—Used for communication among link-local nodes for neighbor discovery and
stateless autoconfiguration. Packets with link-local source or destination addresses are not
forwarded to other links.
• A loopback address—0:0:0:0:0:0:0:1 (or ::1). It has the same function as the loopback address in
IPv4. It cannot be assigned to any physical interface. A node uses this address to send an IPv6
packet to itself.
• An unspecified address—0:0:0:0:0:0:0:0 (or ::). It cannot be assigned to any node. Before
acquiring a valid IPv6 address, a node fills this address in the source address field of IPv6 packets.
The unspecified address cannot be used as a destination IPv6 address.