[CentOS] Forcing IPv4 DNS lookups first before IPv6

Tue Apr 5 22:52:13 UTC 2011
Russell Jones <rjones at eggycrew.com>

Thank you!

If forcing it to stop system-wide is not possible, is there any way of 
forcing IPv4 lookups to occur first then?

On 4/4/2011 5:34 PM, Tom H wrote:
> On Mon, Apr 4, 2011 at 10:51 AM, Russell Jones<rjones at eggycrew.com>  wrote:
>> I am having a strange issue with CentOS 5.4 that I cannot seem to solve.
>> Every DNS lookup results in AAAA records being requested first before A
>> records. As a result, this causes a large amount of unnecessary DNS
>> traffic on the network. IPv6 has been completely disabled on these servers:
>> /etc/modprobe.conf, ipv6 off and net-pf-10 off
>> /etc/sysconfig/network, NETWORKING_IPV6=no
>> lsmod | grep ipv6 shows the kernel module no longer loaded.
>> Yet watching TCP dump shows that AAAA records are requested before A
>> records every time a login is requested from one of our local machines
>> to another. Is there some sort of configuration directive I can use to
>> force IPv4 lookups first before IPv6? Or even better, stop IPv6 lookups
>> all together?
> Disabling ipv6 transport cannot prevent applications from making ipv6
> queries - short of recompiling them as ipv4-only applications or
> having applications check whether there is a non-link-local ipv6
> address before making an ipv6 query. I've seen these checks discussed
> but I don't think that they've been implemented - or, if they've been
> implemented, backported to CentOS 5. It's been going on for a while:
> https://www.redhat.com/archives/redhat-list/2009-March/msg00067.html
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