A DNS question re 6to6/IPv6 host IN A records.

[Jeroen Massar]

Robert wrote:

<SNIP>

> I'd really like to have the program Shoutcast Server
(www.shoutcast.com)
> able to run on the 6bone, able to listen to IPv6 addreses, but the
authors aren't answering me :-)
> I believe that as applications that are mainstream increase in
availability,
> more people will want to move across, even if it's only initially
running dual-stack.
You could try ice-cast IPv6...
Find it on: http://www.bugfactory.org/~gav/ipv6/

>> it depends on how you run your IPv4/v6 servers.  for instance, we are
>> running ftp.iij.ad.jp, one of the most famous anonymous ftp server in
>> Japan, dual-stacked.  this is because we think it robust enough.
> That's what it's all about. Robustness. And that takes management.

>>
>> - "AAAA" record for www.iij.ad.jp points to another one, which NFS-
>>   mounts the data partition from IPv4 one.
> interesting idea...

http://www.ipng.nl runs IPv6 & IPv4 in one Apache 1.3
http://games.concepts.nl runs IPv6 & IPv4 in one Apache 2.0.32 and it's
'abused' for a nice caching trick to allow IPv4-only webservers, like
the current available IIS :(, to be accessed over IPv6:

<VirtualHost *>
        ServerAdmin webmaster@example.org
        ServerName www.example.org
        ServerAlias www.ipv6.example.org
        ProxyRequests On
        ProxyPass / http://www.ipv4.example.org/
        ProxyPassReverse / http://www.ipv4.example.org/
</VirtualHost>

In your dns:
www.example.org.		IN A		172.16.1.1
				IN AAAA	3ffe:8114::1
www.ipv4.example.org.	IN A		172.16.1.1
www.ipv6.example.org.	IN AAAA	3ffe:8114::1

The "trick":

IPv4-only browser:
 - connects to www.example.org over IPv4

IPv6-only (or dualstack but IPv6-try-first-IPv4-as-fallback) browser:
 - connects to www.example.org over IPv6
 the proxy on 3ffe:8114::1 see's "www.example.org" Apache matches that
as a vhost.
 and redirects the query to www.ipv4.example.org (172.16.1.1) which is
an IIS or other IPv4-only box.

Two warns:
 - add trailing slash ('/') to the ProxyPass & ProxyPassReverse
 - either
    use a hostname with only a v4 alias, thats why I have the
www.ipv4.example.org
   or
    use a "ProxyRemote * http://proxy.example.org" passing all the
requests through a IPv4-only proxy.
   Otherwise the proxy-apache will try the IPv6 version (the local
version) and start looping ;)

This allows one to 'experiment' with the whole IPv6/IPv4 stuff without
'hazarding' your IPv4 servers.
Also users who _do_ have IPv6 connectivity will have a fallback when the
IPv6 server is down.
And for log-fetisches, the proxied hosts can be configged to do
customlogs per vhost ;)
This setup works quite well btw and saves on the hassle of setting up
NFS on NT boxes (it can be done ofcourse, but NFS doesn't know much
about NTFS acl's, and with this transparent proxy everything is kept
transparent, it's all in the name ;)

Greets,
 Jeroen