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