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Re: IPV6 in enterprise best practices/white papaers
From: William Herrin <bill () herrin us>
Date: Sun, 27 Jan 2013 12:31:37 -0500

On Sat, Jan 26, 2013 at 5:38 PM, Mark Andrews <marka () isc org> wrote:
In message <CAP-guGX01KLj2cG3ASmfXbmpxZ6j=i1b0DZ++s4-W8Uq_vy-5Q () mail gmail com>, William Herrin writes:
In their infinite(simal) wisdom the architects of IPv6 determined that
a host configured with both a global scope IPv6 address and an IPv4
address will attempt IPv6 in preference to IPv4. If you configure IPv6
on a LAN without first installing your IPv6 Internet connection, that
LAN will break horribly.

The default is to tune for IPv6 first but it been configurable for
years now.  Given one generally wants to use IPv6 over IPv4 to avoid
having you packets going through CGN boxes this is a good thing for
you and your ISP.

Right. On a each local machine you can often override the default
behavior. That default dynamically kicks in for all machines as soon
as there's an IPv6 router on the LAN. Configurable? Sort of. Realistic
solution to the cited problem? Not in your wildest dreams.

As for "breaking" your LAN, if the applications take 60 seconds to
fallback to the other address they were already broken.  Go complain
to your application vendor.  Some vendors have already fixed this
problem with their applications.

That's right, blame the applications for the defective API. After all,
any skilled application programmer can work around the problem, given
sufficiently long experience with IPv6.

Bill Herrin

William D. Herrin ................ herrin () dirtside com  bill () herrin us
3005 Crane Dr. ...................... Web: <http://bill.herrin.us/>
Falls Church, VA 22042-3004

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