DNS NS Question
brad at stop.mail-abuse.org
Mon Nov 14 19:01:21 UTC 2005
At 2:07 PM +0000 2005-11-13, News wrote:
> Does the DNS resolveer work like this.
> Try ns1.example.net if there is no host found then it tries
> ns2.example.net and so on. So it keeps working its way down until
> one of the NS servers says it can Resolve the query?
The resolver will retry the query and try alternative servers,
but a lot depends on the order in which the records have been given
to it, and what information it already has about which servers.
> Or does it simply make a dns type query if it is not found then
> say that is not there Return host not found.
No, it will try more than once.
> So the multiple NS
> records just mean if it can make a tcp connection To the first
> it tries the next one.
The resolver won't fall back to TCP unless there is a truncation
with the data returned via UDP.
> This is what I am trying to understand how
> it works?
The best explanation I know of can be found in the book _DNS and
BIND_ by Paul Albitz and Cricket Liu. If you want to understand how
DNS works, buy a copy of this book, but make sure you get 4th edition.
Brad Knowles, <brad at stop.mail-abuse.org>
"Those who would give up essential Liberty, to purchase a little
temporary Safety, deserve neither Liberty nor Safety."
-- Benjamin Franklin (1706-1790), reply of the Pennsylvania
Assembly to the Governor, November 11, 1755
SAGE member since 1995. See <http://www.sage.org/> for more info.
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