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I'm having a problem with my machine. A site that I used to be able to access is no longer being found. After running nslookup, I notice that about 9 times out of 10 it returns a specific IP which times out if I ping it, but about 1 in 10 times it returns a different IP which works when I ping it.

I've even tried adding an option parameter into nslookup to hit different DNS servers (such as Google's public DNS) and am getting the same result.

Any idea what would cause the IP returned by DNS lookup to change back and forth like that?

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migrated from stackoverflow.com Mar 15 '11 at 22:39

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Is it a server running something popular? Could this be DNS-based load balancing (gone terribly wrong)? –  Matti Virkkunen Mar 14 '11 at 23:45

2 Answers 2

The DNS server sending you the result might be advertising different IPs for a bunch of reasons, e.g load balancing.

Turns out you don't have access to the one it sends for you.

use dig command and whois command on unix for more info on the DNS behavior of the target.

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It is very likely configuration DNS. You can circumvent this on your end, however, by creating an entry in your hosts file for the domain in question.

Here is how to do that on windows: http://vlaurie.com/computers2/Articles/hosts.htm

On Mac OS X: http://decoding.wordpress.com/2009/04/06/how-to-edit-the-hosts-file-in-mac-os-x-leopard/

And on linux: http://linux.about.com/od/lna_guide/a/gdelna46.htm

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