[CentOS] how do I find out which nameserver returns a DNS query?
Rudi Ahlers
Rudi at SoftDux.com
Mon Jul 7 16:03:09 UTC 2008
Ken Price wrote:
> This line ...
>
>> ;; SERVER: 4.2.2.1#53(4.2.2.1)
>
> ... tells you the DNS server which returned the result, which in this
> case, is more than likely a caching (recursive) DNS server. If
> verbose enough logging is enabled on that caching server, it should
> tell you which primary DNS server returned a particular query result.
> The "@ns1.myserver" feature in DIG allows you to do that test directly
> from your workstation to the primary DNS server(s). Is there any
> particular reason this won't work for you? Perhaps if you explained
> your problem in more detail, someone on this list could offer
> alternative methods of troubleshooting.
>
> Regards,
> Ken
>
>
>
>
> ----- Message from Rudi at SoftDux.com ---------
> Date: Mon, 07 Jul 2008 17:38:22 +0200
> From: Rudi Ahlers <Rudi at SoftDux.com>
> Reply-To: CentOS mailing list <centos at centos.org>
> Subject: Re: [CentOS] how do I find out which nameserver returns a
> DNS query?
> To: CentOS mailing list <centos at centos.org>
>
>
>
>>>>
>>>
>> Hi Ken
>>
>> I thought dig would return it, but it doesn't.
>>
>> Look at this:
>>
>>
>> dig hfserver1.hostfactor.co.za
>>
>> ; <<>> DiG 9.3.3rc2 <<>> hfserver1.hostfactor.co.za
>> ;; global options: printcmd
>> ;; Got answer:
>> ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 17016
>> ;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0
>>
>> ;; QUESTION SECTION:
>> ;hfserver1.hostfactor.co.za. IN A
>>
>> ;; ANSWER SECTION:
>> hfserver1.hostfactor.co.za. 6000 IN A 196.34.136.50
>>
>> ;; Query time: 287 msec
>> ;; SERVER: 4.2.2.1#53(4.2.2.1)
>> ;; WHEN: Mon Jul 7 17:36:45 2008
>> ;; MSG SIZE rcvd: 60
>>
>>
>>
>> I know I can dig @server - but I want to know which is the active
>> server that returns a result at the moment
>>
>> --
Ok, sorry, let me re-phrase.
I want to know on my own server, which of my nameservers replied to the
DNS query. In this example 4.2.2.1 is our ISP's upstream DNS server,
which is configured in /etc/resolv.conf - so it should technically
appear there.
But, let's say I query host1.myserver.co.za - and myserver.co.za is on
another server, and has ns1.myserver.co.za, ns2.myserver.co.za,
ns3myserver.co.za & ns4.myserver.co.za
So, as far as I know, any one of those can reply (round robbin DNS?),
but I would like to know which one replies for this particular dig. Is
that possible? I don't want to specify a server to query, I want to find
out which of the 4 returns the query. If it's a cached reply, does it
mean I won't see it?
--
Kind Regards
Rudi Ahlers
CEO, SoftDux
Web: http://www.SoftDux.com
Check out my technical blog, http://blog.softdux.com for Linux or other technical stuff, or visit http://www.WebHostingTalk.co.za for Web Hosting stuff
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