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Re: how to properly add a dns server

On Tue, Mar 12, 2013 at 1:52 AM, Bob Proulx <bob@proulx.com> wrote:
ChadDavis wrote:
> > Why are you overriding the nameserver?  If you control the dhcp server
> > then the better option is to have it provide the desired information
> > there instead of having clients override it.
> I don't want to override it.  I want to add additional nameservers that
> "know" about a domain that I need to resolve.

It doesn't work that way.  Nameservers listed in /etc/resolv.conf are
tried in order.  The first one that can be contacted is the one used.
If a contacted nameserver does not know about a name then it is a
negative response.  No other nameservers are contacted.

The reason for listing up to three nameservers is that if one is
offline then it will fall through to the next one.  But when the first
one answers then the answer it provides will be authoritative.  See

Ok. I believe you are correct on this behavior, i.e. if I have two DNS nameservers configured, the second one is purely a failover.  In other words, if the first one can't resolve a given hostname, it does NOT then consult the second one.  The second nameserver is only contacted if the first one is down.  This is what I understand you to have said.  And I do believe you.  

But when I try to resolve a hostname that I know isn't valid, it sure looks like the second one is consulted.  Here's my output from nslookup on a invalid hostname.

chadmichael@heraclitus:~$ nslookup chad-vm2
;; Got SERVFAIL reply from, trying next server

** server can't find chad-vm2: SERVFAIL

Doesn't this mean that .20 said "I can't resolve that hostname", and this caused a second attempt at my second nameserver .85?  This contradicts what I thought you had explained.  How does this all relate?

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