Question about "proper" way to run v6/v4 website

Gert Doering gert at
Fri Apr 20 08:59:32 CEST 2007


On Thu, Apr 19, 2007 at 02:49:35PM -0400, Tim wrote:
> > Tim, at this point the concept of anything being IPv6-only is not the 
> > brightest of ideas. The IPv6 world is still a little drop in the ocean. 
> > :-(
> Well my point isn't to set up an IPv6-only website.  My point is to
> provide an IPv6 website without negatively impacting customers who have
> IPv6 software but don't realize it.

>From our experience, having had an AAAA record on for about
5 years now, the problem isn't as big as folks claim it to be.

Yes, firefox will do an AAAA lookup, and then fire up an IPv6 TCP SYN
packet - but if the machine has no IPv6 connectivity (which happens a
lot to me, when I'm travelling, and my notebook is in a network that
has only IPv4) the network stack will immediately return "no route to host"
and firefox will fallback to IPv4 connections.

(This is on Gentoo Linux, but I would assume the same behaviour from any
sane operating system.  Vista does it even more clever, it won't even
try the IPv6 connect before IPv4 if there is no native IPv6 connectivity).

> Ok, so it so perhaps instead of providing only AAAA glue, I should
> provide both A and AAAA (assuming my upstream permits it), and then I
> could try distributing AAAA records for my website only over the IPv6
> server?  This IPv6 DNS server could distribute A as well, in case
> there's some problem with website AAAA connectivity (mentioned
> previously int he thread).

The transport protocol used for DNS queries is very much unrelated to
the transport protocol used later on for web access.

Imagine a user with no v6 connectivity sending the query to their 
provider's recursive DNS server, who *has* v4+v6 connectivity, and prefers
v6 - then you will see the DNS query coming over v6, but the user can't
use v6 at all.  (Which is what would happen for most of our customers,
as all of our DNS servers are fully dual-stacked, but most customers are
not yet v6-capable).

Gert Doering
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