Chapter 1 IPv6 Address Configuration
Table 1-4 Structures of Link-local Address and Site-local Address
Link-local Address
10
54
64
1111111010
0
Interface identifier
Site-local Address
10
38
16
64
1111111011
0
Subnet
identifier
Interface identifier
Link-local addresses are used in single network link for host numbering. The
address identified by the first ten bits of the prefix is the link-local address. Routers
do not process the packets with link-local addresses at their source end and
destination end because they will never forward these packets.
The middle 54 bits of this address are set to zero, its 64-bit interface identifier is in
the same IEEE structure as mentioned in the foregoing paragraphs, and the part
of this address space allows some networks to connect up to 2
64
-1 hosts.
Link-local addresses are used for the single network link and site-local addresses
are used for sites. It means that site-local addresses can be used to transmit data
in the interconnected networks but cannot be directly routed to the global Internet
from a site.
Routers within a site can only forward packets within the site instead of forwarding
them outside of the site. The 10-bit prefix of a site-local address is immediately
followed by a succession of zeros, which is slightly different from that of a link-local
address. The subnet identifier of a site-local address is 16-bit, and its interface
identifier is still the 64-bit IEEE-based address.
l
Open Systems Interconnection (
) Network Service Access Point (
)
Address and Internetwork Packet Exchange (
) Address
One of the IPv6 objects is to unify the whole network world for among networks
of IP, IPX and OSI. To support this interoperability, IPv6 reserves 1/128 address
space for OSI NSAP address and network IPX address respectively.
At present, the IPX addresses have not been precisely defined. Refer to RFC
1888 (OSI NSAP and IPv6) for description of the NSAP address allocation.
2.
Multicast Address
The format of the IPv6 multicast address is different from that of the IPv6 unicast
address. Multicast addresses can only be used as destination addresses. No packet
uses a multicast address as the source address.
shows the format of a
multicast address.
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