[CentOS] Slow domain resolution problem

Wed Aug 25 12:37:52 UTC 2010
Les Mikesell <lesmikesell at gmail.com>

On 8/25/10 7:26 AM, Gabriel Tabares wrote:
>> Not sure if it is RDNS.
>> I had similar issues on Fedora, and for me it was to do with IP6.
>> Konqueror web browser took ages to load a page. IIRC Firefox handled
>> it OK.
>> Try Googling for 'uninstalling ipv6 linux'
> I already tried that. The /etc/sysconfig/network has the IPV6_ENABLE=no.
> Disabling the ip6 modules is not feasible, as the bonding module depends
> on it.
>> Another thing is how many DNS IP addresses do you have in
>> /etc/resolv.conf?
> I don't have an ISP DNS,  but the address of the internal DNS server,
> which has all the mappings for our domain.

Do you have two of them?  The usual cause of noticeable slowness is that the 
first one is not responding so you fail to the 2nd.  Or you are looking up 
unqualified hostnames and the clients have several domains in their search list 
and the one that succeeds isn't first.

If your main DNS server is slow, you could run a caching version locally - just 
add your main server as a 'forwarder' in named.conf and set resolve.conf to use first.

   Les Mikesell
    lesmikesell at gmail.com