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

Stephane Bortzmeyer bortzmeyer at nic.fr
Wed Nov 3 16:22:42 UTC 2010

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

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

> 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.


> 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

; EDNS: version: 0, flags:; udp: 4096
;onlyv6.com.                    IN      AAAA

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

onlyv6.com.             172671  IN      NS      ns1.onlyv6.com.
onlyv6.com.             172671  IN      NS      ns2.onlyv6.com.

;; Query time: 0 msec
;; WHEN: Wed Nov  3 17:21:40 2010
;; MSG SIZE  rcvd: 103

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