Unique Local Addresses - Cisco Nexus 7000 Series Configuration Manual

Information About IPv6
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Figure 3-3

Unique Local Addresses

A unique local address is an IPv6 unicast address that is globally unique and is intended for local
communications. It is not expected to be routable on the global Internet and is routable inside of a limited
area, such as a site and it may be routed between a limited set of sites. Applications may treat unique
local addresses like global scoped addresses.
A unique local address has the following characteristics:
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Figure 3-4
Figure 3-4
Local IPv6
Cisco Nexus 7000 Series NX-OS Unicast Routing Configuration Guide, Release 4.x
3-6
IPv4-Compatible IPv6 Address Format
96 bits
0
::192.168.30.1
= ::C0A8:1E01
It has a globally unique prefix (it has a high probability of uniqueness).
It has a well-known prefix to allow for easy filtering at site boundaries.
It allows sites to be combined or privately interconnected without creating any address conflicts or
requiring renumbering of interfaces that use these prefixes.
It is ISP-independent and can be used for communications inside of a site without having any
permanent or intermittent Internet connectivity.
If it is accidentally leaked outside of a site via routing or Domain Name Server (DNS), there is no
conflict with any other addresses.
shows the structure of a unique local address.
Unique Local Address Structure
/7
FC00
Global ID 41 bits
Subnet prefix
Link prefix
• Prefix — FC00::/7 prefix to identify local IPv6 unicast addresses.
Global ID — 41-bit global identifier used to create a globally unique prefix.
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Subnet ID — 16-bit subnet ID is an identifier of a subnet within the site.
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• Interface ID — 64-bit IID
32 bits
IPv4 address
/48 /64
Interface ID
Chapter 3 Configuring IPv6
OL-20002-02