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What is non-authoritive answer in nslookup?

Posted on 2009-04-18
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Last Modified: 2012-05-06
Does it mean the answer I got is not from the reliable source? how to get the 'authoritative' answer?
bash-3.2$ nslookup google.com
Server:		4.2.2.1
Address:	4.2.2.1#53
 
Non-authoritative answer:
Name:	google.com
Address: 74.125.67.100
Name:	google.com
Address: 209.85.171.100
Name:	google.com
Address: 74.125.45.100

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Question by:beer9
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fdduran earned 600 total points
ID: 24176031
It means your dns server (4.2.2.1) had to query google's dns servers for obtaining ns lookup answer. You may ask googles ns server directly by using the code below.
It works in the following way:
nslookup   name_to_lookup   server_to_ask_to
Otherwise it defaults to your local network (or your ISP) dns server.
~$ nslookup google.com ns1.google.com
Server:		ns1.google.com
Address:	216.239.32.10#53
 
Name:	google.com
Address: 74.125.67.100
Name:	google.com
Address: 74.125.45.100
Name:	google.com
Address: 209.85.171.100

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by:arnold
arnold earned 400 total points
ID: 24176442
Not Authoritative DNS response means that the DNS server providing the answer is not directly responsible for the zone.  I.e. from a Caching server.
The 4.2.2.1 is your Providers Caching DNS server.

This is similar to you asking person A for some information. Person A does not have the information, but person A knows that person B should have the information.  Person A gets the answer from Person B and provides it to you.
While you received a response, it is not authoritative since it did not come directly from Person B.

Is there a particular concern you are trying to address?
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by:beer9
ID: 24177679
I see this configuration in /etc/resolv.conf where 192.168.0.1 is my netgear wifi router. so 192.168.0.1 is serving as both the default gateway and default DNS server. I am not sure whether there is any DNS server is running on 192.168.0.1. But still it is helping to resolve the DNS name. I can not telnet to 192.168.0.1 on port 53

I have configured 4.2.2.1 and 4.2.2.2 as the primary and secondary DNS server in my wifi router(192.168.0.1). How this name query transaction is happening?
bash-3.2$ cat /etc/resolv.conf 
nameserver 192.168.0.1
 
---
 
bash-3.2$ telnet 192.168.0.1 53
Trying 192.168.0.1...
^C
bash-3.2$
 
---
 
bash-3.2$ nslookup google.com 
Server:		192.168.0.1
Address:	192.168.0.1#53
 
Non-authoritative answer:
Name:	google.com
Address: 74.125.67.100
Name:	google.com
Address: 209.85.171.100
Name:	google.com
Address: 74.125.45.100

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by:omarfarid
ID: 24178014
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Expert Comment

by:arnold
ID: 24179764
In short DNS works on both UDP and TCP port 53.  The TCP connection mode is used for large data transfers.  Normally routers that provide dns responses only listen on UDP 53 port only.
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Author Closing Comment

by:beer9
ID: 31571810
Thank you :-)
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