[dns-operations] resolv.conf and resolving IPv6-only domains/NSes

[Frank Bulk - iName.com]

Stephane:

You are correct, whether my tool requests resolution via IPv4 or IPv6 for
onlyv6.com shouldn't matter as long as the queried resolver has IPv6
connectivity.

So what I've learned is that if I want to resolve query v6-only domains,
such as onlyv6.com, I had better make sure that the first DNS server in my
resolv.conf has IPv6 connectivity.  Even better, make sure all of them do.

Frank

-----Original Message-----
From: Stephane Bortzmeyer [mailto:bortzmeyer at nic.fr] 
Sent: Wednesday, November 03, 2010 11:23 AM
To: Frank Bulk - iName.com
Cc: dns-operations at dns-oarc.net
Subject: Re: resolv.conf and resolving IPv6-only domains/NSes

On Wed, Nov 03, 2010 at 10:59:34AM -0500,
 Frank Bulk - iName.com <frnkblk at iname.com> wrote 
 a message of 42 lines which said:

> I noticed that if an external IPv6 DNS server was not first in the
> resolv.conf, that "dig AAAA onlyv6.com" would consistently fail

A big warning: the fact that you query the recursive name server with
IPv4 or v6 is unrelated to the fact that the name server is able to
query v6-only domains or not.

> When I run "dig AAAA onlyv6.com" against the first IPv4 DNS server, I get
a
> SERVFAIL.

It seems this server has no IPv6 connectivity at all. If so, bad
server.

> It seems like host resolution using resolv.conf starts from the top
> of resolv.conf going on down, and if there's a SERVFAIL on the
> first, it doesn't go to the second entry.

Yes.

> Can someone else test and see if this WAD or something else?

Here is an example of a name server queried with IPv4 (Debian 5, too):

% dig AAAA onlyv6.com    

; <<>> DiG 9.6-ESV-R1 <<>> AAAA onlyv6.com
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 45931
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 2, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
;; QUESTION SECTION:
;onlyv6.com.                    IN      AAAA

;; ANSWER SECTION:
onlyv6.com.             3471    IN      AAAA    2607:f118:8c0:800::64

;; AUTHORITY SECTION:
onlyv6.com.             172671  IN      NS      ns1.onlyv6.com.
onlyv6.com.             172671  IN      NS      ns2.onlyv6.com.

;; Query time: 0 msec
;; SERVER: 127.0.0.1#53(127.0.0.1)
;; WHEN: Wed Nov  3 17:21:40 2010
;; MSG SIZE  rcvd: 103