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m_1607
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DNS Issue

Sun Feb 19, 2012 2:06 am

Hi-

I have a client machine that doesnt respond to internet websites ,but it works perfect with intranet websites .

what could be issue Nslookup for those internet website shows Non Authorative answer.

killabee
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Re: DNS Issue

Sun Feb 19, 2012 2:48 am

'Non authoritative answer' is normal. It just means that the query was answered by a DNS server that doesn't own the domain you queried. The answer would be considered authoritative if you queried the responsible name server yourself.

Check if that machine is behind a proxy blocking external sites...or if an internal firewall or other device blocks http/https traffic to the outside.

m_1607
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Re: DNS Issue

Sun Feb 19, 2012 3:09 am

there is no proxy server either firewall is not blocking http and https traffic.

Reggle
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Re: DNS Issue

Tue Feb 21, 2012 12:59 pm

What happens when you ping an external website? It works, times out, or can't perform DNS lookup?
http://reggle.wordpress.com

Morphic
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Re: DNS Issue

Tue Feb 21, 2012 5:21 pm

Try this...

ping google.com
(do you get 4 replies?)
ping 74.125.237.43
(do you get 4 replies?)

telnet google.com 80
(do you get something like this after hitting enter a few times -
HTTP/1.0 400 Bad Request
Content-Type: text/html; charset=UTF-8
Content-Length: 925
Date: Tue, 21 Feb 2012 22:17:37 GMT
Server: GFE/2.0

<!DOCTYPE html>
<html lang=en>
<meta charset=utf-8>
<meta name=viewport content="initial-scale=1, minimum-scale=1, width=device-w
idth">
<title>Error 400 (Bad Request)!!1</title>
<style>
*{margin:0;padding:0}html,code{font:15px/22px arial,sans-serif}html{
background:#fff;color:#222;padding:15px}body{margin:7% auto 0;max-width:390px;min-height:180px;padding:30px 0 15px}* > body{backgr
ound:url(//www.google.com/images/errors/robot.png) 100% 5px no-repeat;padding-right:205px}p{margin:11px 0 22px;overflow:hidden}ins
{color:#777;text-decoration:none}a img{border:0}@media screen and (max-width:772px){body{background:none;margin-top:0;max-width:no
ne;padding-right:0}}
</style>
<a href=//www.google.com/><img src=//www.google.com/images/errors/logo_sm.gif alt=Google></a>
<p>
<b>400.</b> <ins>ThatÔÇÖs an error.</ins>
<p>Your client has issued a malformed or illegal request. <ins>ThatÔÇÖs all we know.</ins>

Or do you get some kind of error?

Then try this

telnet 74.125.237.43 80
and what happens?

If you can telnet/ping IPs but not DNS names, you have an issue with DNS. If you can't do either, you have something blocking your communication outbound (Proxy/firewall).

Hope that helps!

m_1607
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Re: DNS Issue

Wed Feb 22, 2012 4:11 am

Does anyone help me with understanding how open dns works.

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davidrothera
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Re: DNS Issue

Wed Feb 22, 2012 5:12 am

OpenDNS is just a DNS resolver which is open and free to use by anyone.

Traditionally you would typically have used DNS resolvers that were provided/operated by your ISP (if you didn't know any better) and sometimes these servers can be a little slow / underpowered and therefore give you a slower browsing experience.

Have a read through this: http://www.opendns.com/business-solutio ... /benefits/
---
David
CCIE R&S #38338, CCIP, CCNP

http://networkbroadcast.co.uk - My Blog
http://twitter.com/davidrothera

m_1607
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Re: DNS Issue

Mon Feb 27, 2012 1:43 am

one more question how can we calculate how much time does a client take to resolve particular Domain name to IP from DNS server
is there any software that we can try with ?

killabee
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Re: DNS Issue

Mon Feb 27, 2012 2:32 am

Dig does that.

Example:
Code: Select all
Mac:~ killabee$ dig yahoo.com

; <<>> DiG 9.7.3-P3 <<>> yahoo.com
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 46291
;; flags: qr rd ra; QUERY: 1, ANSWER: 3, AUTHORITY: 0, ADDITIONAL: 0

;; QUESTION SECTION:
;yahoo.com.         IN   A

;; ANSWER SECTION:
yahoo.com.      3269   IN   A   209.191.122.70
yahoo.com.      3269   IN   A   98.139.127.62
yahoo.com.      3269   IN   A   98.139.183.24

;; Query time: 82 msec <----------------------------------- Here
;; SERVER: 8.8.8.8#53(8.8.8.8)
;; WHEN: Mon Feb 27 02:30:55 2012
;; MSG SIZE  rcvd: 75

m_1607
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Re: DNS Issue

Mon Feb 27, 2012 3:21 am

If I want to check from windows server how do we do that

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mellowd
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Re: DNS Issue

Mon Feb 27, 2012 3:22 am

Install cygwin

'

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