Disable IPv6 by default.

[John Reiser]

>  What's so scary about IPv6, anyway?

0) There exists > $1.0e10 of routers and switches that do not grok IPv6.
   Replacing or enhancing them will cost about that much more.
1) Many ISPs charge more for service via IPv6 than via IPv4.
   In some large markets in the US, every DSL and cable ISP either
   charges more, or does not offer IPv6 at all.
2) Most default configurations of IPv6, including Fedora,
   are about as unfriendly as possible towards inexpensive anonymity.
   (The default MAC address is part of the IPv6 address, etc.)
   Most environments, including Fedora, provide no ready means
   to ameliorate the increased risks.

> Anything that justifies blowing
> off all the efforts many people have made at maturing the standard?

http://cr.yp.to/djbdns/ipv6mess.html
and there has been little or no progress for a *decade*.
[Executive summary: there is no reasonable transition plan.
There cannot be any such plan because of the design of IPv6.]

--