About IPv6
S e n d d o c u m e n t a t i o n c o m m e n t s t o m d s f e e d b a c k - d o c @ c i s c o . c o m
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Extended IPv6 Address Space for Unique Addresses
IPv6 extends the address space by quadrupling the number of network address bits from 32 bits (in IPv4)
to 128 bits, which provides many more globally unique IP addresses. By being globally unique, IPv6
addresses enable global reachability and end-to-end security for networked devices, functionality that is
crucial to the applications and services that are driving the demand for more addresses.
IPv6 Address Formats
IPv6 addresses are represented as a series of 16-bit hexadecimal fields separated by colons (:) in the
format x:x:x:x:x:x:x:x. The following are examples of IPv6 addresses:
It is common for IPv6 addresses to contain successive hexadecimal fields of zeros. To make IPv6
addresses easier to use, two colons (::) may be used to compress successive hexadecimal fields of zeros
at the beginning, middle, or end of an IPv6 address (the colons represent successive hexadecimal fields
of zeros).
Note
Two colons (::) can be used only once in an IPv6 address to represent the longest successive hexadecimal
fields of zeros.
The hexadecimal letters in IPv6 addresses are not case-sensitive.
Note
Table 47-1
IPv6 Address Type
Unicast
Multicast
Cisco MDS 9000 Family CLI Configuration Guide
47-2
IPv6 Address Formats, page 47-2
IPv6 Address Prefix Format, page 47-3
IPv6 Address Type: Unicast, page 47-3
IPv6 Address Type: Multicast, page 47-5
ICMP for IPv6, page 47-6
Path MTU Discovery for IPv6, page 47-7
IPv6 Neighbor Discovery, page 47-7
Router Discovery, page 47-9
IPv6 Stateless Autoconfiguration, page 47-9
Dual IPv4 and IPv6 Protocol Stacks, page 47-10
2001:0DB8:7654:3210:FEDC:BA98:7654:3210
2001:0DB8:0:0:8:800:200C:417A
Table 47-1
lists compressed IPv6 address formats.
Compressed IPv6 Address Formats
Uncompressed Format
2001:0DB8:800:200C:0:0:0:417A 2001:0DB8:800:200C::417A
FF01:0:0:0:0:0:0:101
Chapter 47
Configuring IPv6 for Gigabit Ethernet Interfaces
Compressed Format
FF01::101
OL-18084-01, Cisco MDS NX-OS Release 4.x