7/31/2019 An IPv6 Address Consists of 128 Bits
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An IPv6 address consists of 128 bits.[1] Addresses are
classified into various types for applications in the major
address
and routing methodologies: unicast, multicast, and anycast
networking. In each of these, various address formats are
ecognized by logically dividing the 128 address bits into bit
groups and establishing rules for associating the values ofhese bit
groups with special addressing features.
Unicast address format
Unicast and anycast addresses are typically composed of two
logical parts: a 64-bit network prefix used forrouting, an
64-bit interface identifier used to identify a host's network
interface.
General unicast address format
bits 48 16
field routing prefix subnet id
The network prefix is contained in the most significant 64 bits
of the address. The recommended allocation to end user
a 48-bit routing prefix. In this scenario, the 16 bits of
thesubnet id(entifier) field are available to the network
administrator to define subnets within the given network. The
64-bit interface identifieris either automatically generatfrom the
interface's MAC address using themodified EUI-64format, obtained
from a DHCPv6 server, automatically
stablished randomly, or assigned manually.
A link-local address is also based on the interface identifier,
but uses a different format for the network prefix.
Link-local address format
bits 10 54
field prefix zeroes
Theprefix field contains the binary value 1111111010. The 54
zeroes that follow make the total network prefix the sam
for all link-local addresses, rendering them non-routable.
Multicast address format
For more details on this topic, see Multicast address#IPv6 .
Multicast addresses are formed according to several specific
formatting rules, depending on the application.
General multicast address format
bits 8 4 4 112
field prefix flgs sc group ID
Theprefix holds the binary value 11111111 for any multicast
address. Currently, 3 of the 4 flag bits in theflgs field ar
defined;[1] the most-significant flag bit is reserved for future
use. The 4-bitsc (or scope) field is used to indicate where
address is valid and unique.
Solicited-Node multicast address format
bits 8 4 4 79
field prefix flgs sc zeroes
Theprefix andsc fields hold the binary values 11111111 and 0010.
Solicited-node multicast addresses are computed a
function of a node's unicast or anycast addresses. A
solicited-node multicast address is created by copying the last 24
bof a unicast or anycast address to the last 24 bits of the
multicast address.
Unicast-prefix-based multicast address format[2][3]
http://en.wikipedia.org/wiki/IPv6_address#cite_note-rfc4291-0http://en.wikipedia.org/wiki/Unicasthttp://en.wikipedia.org/wiki/Anycasthttp://en.wikipedia.org/wiki/Routinghttp://en.wikipedia.org/wiki/MAC_addresshttp://en.wikipedia.org/wiki/IPv6_address#Modified_EUI-64http://en.wikipedia.org/wiki/IPv6_address#Modified_EUI-64http://en.wikipedia.org/wiki/IPv6_address#Modified_EUI-64http://en.wikipedia.org/wiki/DHCPv6http://en.wikipedia.org/wiki/Multicast_address#IPv6http://en.wikipedia.org/wiki/IPv6_address#cite_note-rfc4291-0http://en.wikipedia.org/wiki/IPv6_address#cite_note-rfc4291-0http://en.wikipedia.org/wiki/IPv6_address#cite_note-rfc3306-1http://en.wikipedia.org/wiki/IPv6_address#cite_note-rfc3956-2http://en.wikipedia.org/wiki/Unicasthttp://en.wikipedia.org/wiki/Anycasthttp://en.wikipedia.org/wiki/Routinghttp://en.wikipedia.org/wiki/MAC_addresshttp://en.wikipedia.org/wiki/IPv6_address#Modified_EUI-64http://en.wikipedia.org/wiki/DHCPv6http://en.wikipedia.org/wiki/Multicast_address#IPv6http://en.wikipedia.org/wiki/IPv6_address#cite_note-rfc4291-0http://en.wikipedia.org/wiki/IPv6_address#cite_note-rfc3306-1http://en.wikipedia.org/wiki/IPv6_address#cite_note-rfc3956-2http://en.wikipedia.org/wiki/IPv6_address#cite_note-rfc4291-0
