
Configuring IPv6 Services
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118428-A Rev. A
IPv6 Addresses
An IPv6 address consists of 128 bits that identify an interface or a set of
interfaces. The address consists of two parts: an address prefix and an IPv6
interface ID. The first 3 bits of the address indicate the type of address that follows
-- a unicast address, for example.
F
igure 1-1 shows the basic parts of an IPv6 address.
Figure 1-1. 128-Bit IPv6 Address Format
Address Prefix
The
address prefix
consists of one or more
aggregator addresses
. These addresses
are listed in the hierarchical order of the organizations that issue them.
• At the top of the hierarchy, international registries assign blocks of addresses
to
top-level aggregators
(TLAs). TLA addresses provide the public transit
points where long-haul service providers establish peer connections.
• TLAs allocate blocks of address to the
next-level aggregators
(NLAs), the
large Internet service providers and global corporate networks.
• An NLA that is a service provider further allocates its addresses to its
subscribers, the lowest-level aggregators, the
site-level aggregators
(SLAs).
TLA and NLA addresses are part of the public Internet topology. SLA addresses
are part of private site-level topologies.
Type Address prefix
IPV0003A
InterfaceID ( or Token )
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