That's all fine and dandy and I do realize the need for an extended IP address pool, but if it's starting to affect performance I say fuck IPv6.
Sadly, modern GNU/Linux systems prefer IPv6 addresses over IPv4 when being presented with a choice. I honestly don't see why the fuck IPv6 should be preferred right now as it's bound to be a lot slower on a lot of networks, for the time being at least.
Case in point: Debian's apt-get update over IPv4 and IPv6:
root@box:~# host security.debian.org
security.debian.org has address 195.20.242.89
security.debian.org has address 212.211.132.32
security.debian.org has address 212.211.132.250
security.debian.org has IPv6 address 2001:a78:5:1:216:35ff:fe7f:6ceb
security.debian.org has IPv6 address 2001:8d8:580:400:6564:a62:0:2
security.debian.org has IPv6 address 2001:a78:5:0:216:35ff:fe7f:be4f
security.debian.org mail is handled by 10 chopin.debian.org.IPv6:
root@box:~# time apt-get update
[...]
real 1m18.222s
user 0m7.472s
sys 0m6.948s
root@box:~# time apt-get update
[...]
real 0m13.481s
user 0m7.728s
sys 0m5.332s
So, how do we tell the system to prefer IPv4 addresses over IPv6?
It's rather simple, actually: we need to have a look at getaddrinfo(3)'s configuration file; /etc/gai.conf.Locate this line and uncomment it:
#precedence ::ffff:0:0/96 100
There ya go, IPv4 is preferred now.
This works as that's the special address range to help in the transition from 4 to 6; every IPv4 address can be written as an IPv6 one using that form.
(See http://en.wikipedia.org/wiki/IPv6#IPv4-mapped_IPv6_addresses for more info on that one.)
Anyways, the format is ::ffff:0:0/96 which means that the ipv4 ip address 192.168.18.234/32 will be written as 0:0:ffff:192.168.18.234/128 and will match that line in gai.conf.
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