Strange IPv6 DNS lookups

[Kenneth Holter]

Hello all.


Several of our RHEL-servers are issuing strange DNS lookups. Consider this
example:


*  1   0.000000   1.2.3.4 -> 5.6.7.8   DNS Standard query AAAA **
server1.example-prod.com* <http://server1.example-prod.com/>*
  9   0.007891   1.2.3.4 -> 5.6.7.8   DNS Standard query AAAA
server1.example-prod.com.example-test.local
 11   0.092904   1.2.3.4 -> 5.6.7.82   DNS Standard query A
server1.example-prod.com
 12   0.093356   5.6.7.8 -> 1.2.3.4   DNS Standard query response A 1.2.3.4
*

>From what I can tell, the client first issues two IPv6 DNS lookups, before
falling back to IPv4 lookup. We're not running IPv6 (and our DNS servers do
not support IPv6 lookups), so the client is not getting and answer before
issuing the IPv4 lookup.

I've very puzzled by the second query, in which the FQDN of the lookup query
is appended another domain. I've noticed that the appended domain may be
both the same domain name (i.e. server1.example-prod-com.example-prod.com)
or another domain as in the example above.
Does anyone have a clue as to why such bizarre queries are performed by the
client?

Since we're not running IPv6, I have simply disabled it for this server
(grepping "lsmod" does not return any "ipv6" results). Yet the problem
remains. Does the DNS lookup library automatically issue IPv6 queries before
issuing IPv4 queries? Is there a way to disable IPv6 lookups?


Regards,
Kenneth Holter