Reasons for not resolving
Kevin Darcy
kcd at chrysler.com
Wed Oct 28 16:02:54 UTC 2009
Alans,
Why would you use Google to determine whether a web site is up or not?
It's not even clear to me that you're having a DNS problem. It's rather
bad practice to have lots of reverse-records in the DNS for a given
address (e.g. 96.31.75.113), and can even cause problems with oversized
responses to reverse lookups being dropped by firewalls, but it
shouldn't cause any *forward* (name-to-address) lookups to fail.
Can you resolve a name like yarnandwaste.com or can't you? Please follow
normal diagnostic procedures and try to determine what actual problem
you are having. "Can't ping or browse" is only the start of the
diagnostic process, and might not be caused by DNS at all.
Once you've determined that you can't resolve a particular name, then
something you might try is a "dig +trace" on the name, from your
nameserver. That will show you the sequence of queries that will be
followed by a resolver to try and resolve the name, and might help
pinpoint the source of the problem. It will not, however, exactly match
what your nameserver is doing unless you have a completely "vanilla",
iterative-resolving configuration (i.e. Internet root hints and nothing
else). If you have other elements of your config that affect resolution,
e.g. zones of type stub/forward/master/slave anywhere in the hierarchy
of the name you're looking up, or "forwarders" in your "options" clause,
then "dig +trace" won't know about those "specials" and can't match
exactly what your nameserver would do. Also, it's possible that your
nameserver has cached data that might cause it to resolve differently
than "dig +trace", which always starts with no cache at all.
- Kevin
Alans wrote:
>
> I looked more and I figure out that we can’t ping or browse any of
> these hosts http://www.ip-adress.com/reverse_ip/96.31.75.113 (they all
> are on one IP) it’s confusing because when I search in google for host
> names it appears in the result which means it’s not down fir
> everyone!! Any ideas?
>
> Kind regards,
>
> Alans
>
> *From:* bind-users-bounces at lists.isc.org
> [mailto:bind-users-bounces at lists.isc.org] *On Behalf Of *Alans
> *Sent:* Wednesday, October 28, 2009 10:47 AM
> *To:* bind-users at lists.isc.org
> *Subject:* Reasons for not resolving
>
> Hello,
>
> There are few websites that our DNS (BIND 9.4.2 on CentOS 5) is not
> resolving while others like 4.2.2.2 does, I wonder what could be the
> reasons for this?
>
> Regards,
>
> Alans
>
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