Summary: problem getting address record for google public dns server

M. Meadows sun-guru at live.com
Mon Nov 22 20:49:36 UTC 2010


Thanks to both Stacey and Barry for the feedback. You've answered my question. Sorry I didn't get back with you on this sooner!
 
Marty

 


Date: Wed, 17 Nov 2010 10:01:13 +0000
From: stacey.marshall at oracle.com
To: bind-users at lists.isc.org
Subject: Re: problem getting address record for google public dns server


This crops up time and time again - perhaps +trace should have been +mimic.

The '+trace' option causes dig to act as a recursive server would, asking each server in turn for a none recursive answer.  Thus when you say +trace its your instance of dig that's doing the work.

The details in the response hold your answer:

$ dig @66.231.91.222 google-public-dns-a.google.com       

; <<>> DiG 9.3.6-P1 <<>> @66.231.91.222 google-public-dns-a.google.com
; (1 server found)
;; global options:  printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 503
;; flags: qr rd; QUERY: 1, ANSWER: 0, AUTHORITY: 13, ADDITIONAL: 0

;; QUESTION SECTION:
;google-public-dns-a.google.com.        IN      A

;; AUTHORITY SECTION:
.                       3600000 IN      NS      A.ROOT-SERVERS.NET.
.                       3600000 IN      NS      B.ROOT-SERVERS.NET.
.                       3600000 IN      NS      C.ROOT-SERVERS.NET.
.                       3600000 IN      NS      D.ROOT-SERVERS.NET.
.                       3600000 IN      NS      E.ROOT-SERVERS.NET.
.                       3600000 IN      NS      F.ROOT-SERVERS.NET.
.                       3600000 IN      NS      G.ROOT-SERVERS.NET.
.                       3600000 IN      NS      H.ROOT-SERVERS.NET.
.                       3600000 IN      NS      I.ROOT-SERVERS.NET.
.                       3600000 IN      NS      J.ROOT-SERVERS.NET.
.                       3600000 IN      NS      K.ROOT-SERVERS.NET.
.                       3600000 IN      NS      L.ROOT-SERVERS.NET.
.                       3600000 IN      NS      M.ROOT-SERVERS.NET.

;; Query time: 111 msec
;; SERVER: 66.231.91.222#53(66.231.91.222)
;; WHEN: Wed Nov 17 09:50:35 2010
;; MSG SIZE  rcvd: 259

Looking at the flags in the response note the lack of 'ra'; Recursion Available!

Thus the server is saying I don't know (or I wont tell you what's in my cache) and I'm not going to find an answer for you, go start looking at the root servers.  Hence the +trace works.



Regards
Stacey
On 16/11/2010 21:00, M. Meadows wrote: 


Can someone explain the following dig results? The first dig @8.8.8.8 provides the expected result
 
 
: dig +noall +answer google-public-dns-a.google.com @8.8.8.8
google-public-dns-a.google.com. 85040 IN A      8.8.8.8

We get the same result from KLOTH.NET (http://www.kloth.net/services/nslookup.php)
 
 
But when we specify the public facing exacttarget.com server
 
: dig +noall +answer google-public-dns-a.google.com @66.231.91.222 
 
No answer
 
And when we use +trace ... it seems to find it's way to the correct answer.
 
: dig google-public-dns-a.google.com @66.231.91.222 +trace
; <<>> DiG 9.3.6-P1-RedHat-9.3.6-4.P1.el5_4.2 <<>> google-public-dns-a.google.com @66.231.91.222 +trace
;; global options:  printcmd
.                       3600000 IN      NS      A.ROOT-SERVERS.NET.
.                       3600000 IN      NS      B.ROOT-SERVERS.NET.
.                       3600000 IN      NS      C.ROOT-SERVERS.NET.
.                       3600000 IN      NS      D.ROOT-SERVERS.NET.
.                       3600000 IN      NS      E.ROOT-SERVERS.NET.
.                       3600000 IN      NS      F.ROOT-SERVERS.NET.
.                       3600000 IN      NS      G.ROOT-SERVERS.NET.
.                       3600000 IN      NS      H.ROOT-SERVERS.NET.
.                       3600000 IN      NS      I.ROOT-SERVERS.NET.
.                       3600000 IN      NS      J.ROOT-SERVERS.NET.
.                       3600000 IN      NS      K.ROOT-SERVERS.NET.
.                       3600000 IN      NS      L.ROOT-SERVERS.NET.
.                       3600000 IN      NS      M.ROOT-SERVERS.NET.
;; Received 228 bytes from 66.231.91.222#53(66.231.91.222) in 1 ms
com.                    172800  IN      NS      g.gtld-servers.net.
com.                    172800  IN      NS      f.gtld-servers.net.
com.                    172800  IN      NS      l.gtld-servers.net.
com.                    172800  IN      NS      h.gtld-servers.net.
com.                    172800  IN      NS      j.gtld-servers.net.
com.                    172800  IN      NS      c.gtld-servers.net.
com.                    172800  IN      NS      i.gtld-servers.net.
com.                    172800  IN      NS      d.gtld-servers.net.
com.                    172800  IN      NS      k.gtld-servers.net.
com.                    172800  IN      NS      m.gtld-servers.net.
com.                    172800  IN      NS      a.gtld-servers.net.
com.                    172800  IN      NS      e.gtld-servers.net.
com.                    172800  IN      NS      b.gtld-servers.net.
;; Received 504 bytes from 198.41.0.4#53(A.ROOT-SERVERS.NET) in 35 ms
google.com.             172800  IN      NS      ns2.google.com.
google.com.             172800  IN      NS      ns1.google.com.
google.com.             172800  IN      NS      ns3.google.com.
google.com.             172800  IN      NS      ns4.google.com.
;; Received 184 bytes from 192.42.93.30#53(g.gtld-servers.net) in 75 ms
google-public-dns-a.google.com. 86400 IN A      8.8.8.8
;; Received 64 bytes from 216.239.34.10#53(ns2.google.com) in 39 ms
 
What's going on?
 
Thanks!
Marty
 
 
 

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