Looking at ipv4 vs ipv6 address selection

gai.conf

# Configuration for getaddrinfo(3).
#
# So far only configuration for the destination address sorting is needed.
# RFC 3484 governs the sorting.  But the RFC also says that system
# administrators should be able to overwrite the defaults.  This can be
# achieved here.
#
# All lines have an initial identifier specifying the option followed by
# up to two values.  Information specified in this file replaces the
# default information.  Complete absence of data of one kind causes the
# appropriate default information to be used.  The supported commands include:
#
# reload  <yes|no>
#    If set to yes, each getaddrinfo(3) call will check whether this file
#    changed and if necessary reload.  This option should not really be
#    used.  There are possible runtime problems.  The default is no.
#
# label   <mask>   <value>
#    Add another rule to the RFC 3484 label table.  See section 2.1 in
#    RFC 3484.  The default is:
#
label ::1/128       0
label fc00::/7      1
label ::/0          2
label ::ffff:0:0/96 3
label 2002::/16     4
label 2001:0::/32   5
label ::/96         10
label fec0::/10     11
#
#    This default differs from the tables given in RFC 3484 by handling
#    (now obsolete) site-local IPv6 addresses and Unique Local Addresses.
#    The reason for this difference is that these addresses are never
#    NATed while IPv4 site-local addresses most probably are.  Given
#    the precedence of IPv6 over IPv4 (see below) on machines having only
#    site-local IPv4 and IPv6 addresses a lookup for a global address would
#    see the IPv6 be preferred.  The result is a long delay because the
#    site-local IPv6 addresses cannot be used while the IPv4 address is
#    (at least for the foreseeable future) NATed.  We also treat Teredo
#    tunnels special.
#
# precedence  <mask>   <value>
#    Add another rule to the RFC 3484 precedence table.  See section 2.1
#    and 10.3 in RFC 3484.  The default is:
#
precedence  ::1/128       60
precedence  fc00::/7      50
precedence  ::/0          40
precedence ::ffff:0:0/96  30
precedence  2002::/16     20
precedence  2001::/32     10
precedence ::/96          1
precedence fec0::/10      1
#
#    For sites which prefer IPv4 connections change the last line to
#
#precedence ::ffff:0:0/96  100

#
# scopev4  <mask>  <value>
#    Add another rule to the RFC 3484 scope table for IPv4 addresses.
#    By default the scope IDs described in section 3.2 in RFC 3484 are
#    used.  Changing these defaults should hardly ever be necessary.
#    The defaults are equivalent to:
#
#scopev4 ::ffff:169.254.0.0/112  2
#scopev4 ::ffff:127.0.0.0/104    2
#scopev4 ::ffff:0.0.0.0/96       14
#
#    For sites which use site-local IPv4 addresses behind NAT there is
#    the problem that even if IPv4 addresses are preferred they do not
#    have the same scope and are therefore not sorted first.  To change
#    this use only these rules:
#
#scopev4 ::ffff:169.254.0.0/112  2
#scopev4 ::ffff:127.0.0.0/104    2
#scopev4 ::ffff:0.0.0.0/96       14

Ip addresses

Ip addresses are in 2001::/16

wget -O devnull ipv6.google.com

dreamplug-debian:~# wget -O /dev/null ipv6.google.com
--2012-01-13 12:49:17--  http://ipv6.google.com/
Resolving ipv6.google.com... 2404:6800:4006:800::1011
Connecting to ipv6.google.com|2404:6800:4006:800::1011|:80... connected.
HTTP request sent, awaiting response... 200 OK
Length: unspecified [text/html]
Saving to: `/dev/null'

    [   <=>                                                                                  ] 12,094      20.5K/s   in 0.6s    

2012-01-13 12:49:18 (20.5 KB/s) - `/dev/null' saved [12094]

wget -O devnull www.kame.net

dreamplug-debian:~# wget -O /dev/null www.kame.net
--2012-01-13 12:49:25--  http://www.kame.net/
Resolving www.kame.net... 203.178.141.194, 2001:200:dff:fff1:216:3eff:feb1:44d7
Connecting to www.kame.net|203.178.141.194|:80... connected.
HTTP request sent, awaiting response... 200 OK
Length: unspecified [text/html]
Saving to: `/dev/null'

    [ <=>                                                                                    ] 3,027       --.-K/s   in 0.007s  

2012-01-13 12:49:26 (415 KB/s) - `/dev/null' saved [3027]