The Ethical Hacker Network - Primary and Secondary DNS

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Manu Zacharia (-M-)

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Primary and Secondary DNS

« on: September 05, 2006, 01:32:22 AM »

Hi All,

Recently I came across a book on Ethical Hacking. One of the chapters talk about DNS as follows:

Quote

"A DNS Server is basically a server running DNS software. The server that the browser first looks for a translation is the Primary DNS Server, if this doesn't show any match, then it contacts another DNS server somewhere on the Internet, or the Secondary DNS server. If a match is found on the Secondary server, then the Primary server updates its database so that it doesn't have to contact the Secondary server again for the same match."

I was under the impression that the browser will contact the Primary DNS Server and if the DNS Server is alive and not able to resolve the name, the browser will not contact the secondary DNS Server as the primary DNS server is running. The secondary DNS server is contacted only when the primary DNS server is down due to some reason.

After reading the above quoted paragraph, I am in a little bit confustion.

Please comment on this.

Regards,

The Morpheus


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Manu Zacharia
MVP (Enterprise Security), ISLA-2010 (ISC)², C|EH, C|HFI, CCNA, MCP,
Certified ISO 27001:2005 Lead Auditor

There are 3 roads to spoil; women, gambling & hacking. The most pleasant with women, the quickest with gambling, but the surest is hacking - c0c0n

pcsneaker

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Re: Primary and Secondary DNS

« Reply #1 on: September 05, 2006, 02:13:09 AM »

You are right. The authors of that book obviously don't have much clue about how DNS works.


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jimbob

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Re: Primary and Secondary DNS

« Reply #2 on: September 05, 2006, 04:23:10 AM »

Yes, I'd second that. Note that you'll only contact the secondary DNS server if the primary is unavailable. If the primary is up and a host/IP address lookup fails the client won't contact the secondary since it will have received an error message back from the primary.

Jim


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Manu Zacharia (-M-)

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Re: Primary and Secondary DNS

« Reply #3 on: September 05, 2006, 08:51:51 PM »

Hi All,

Thanks for the answer. I am planning to write to the Author and the Publisher of the Book regarding the wrong info.

However, for doing the same, I need some references or materials either from the Internet or some other resources. I have tried googling, but infortunately almost all of the articles talk about the Primary and Secondary DNS Zones rather than on the Primary and Secondary DNS Server name resolution approach or process. If any of you have come across any resources that explicitly says about the subject matter, plese post is there.

Regards,

The Morpheus