Operation Manual

is dened by indicating the length of the prex after a slash at the end of the address.
An address, as shown in Example 13.4, “IPv6 Address Specifying the Prex
Length” (page 234), contains the information that the rst 64 bits form the network part
of the address and the last 64 form its host part. In other words, the 64 means that the
netmask is lled with 64 1-bit values from the left. Just like with IPv4, the IP address
is combined with AND with the values from the netmask to determine whether the host
is located in the same subnetwork or in another one.
Example 13.4:
IPv6 Address Specifying the Prex Length
fe80::10:1000:1a4/64
IPv6 knows about several predened types of prexes. Some of these are shown in
Table 13.4, “Various IPv6 Prexes” (page 234).
Table 13.4:
Various IPv6 Prexes
DenitionPrex (hex)
IPv4 addresses and IPv4 over IPv6
compatibility addresses. These are used
00
to maintain compatibility with IPv4.
Their use still requires a router able to
translate IPv6 packets into IPv4 pack-
ets. Several special addresses, such as
the one for the loopback device, have
this prex as well.
Aggregatable global unicast addresses.
As is the case with IPv4, an interface
2 or 3 as the rst digit
can be assigned to form part of a cer-
tain subnetwork. Currently, there are
the following address spaces:
2001::/16 (production quality ad-
dress space) and 2002::/16 (6to4
address space).
Link-local addresses. Addresses with
this prex should not be routed and
fe80::/10
should therefore only be reachable
from within the same subnetwork.
234 Reference