resolver search order question

[Norman P. B. Joseph]

But I wasn't asking about multiple "nameserver" directives in
resolv.conf, I was asking about multiple domains in a "search"
directive.

You're saying getting a NODATA response for "aj-mail1.ctc.com" (tagging
on the first domain in the search directive) would cause the resolver to
return that as a definitive answer and to not consult other nameservers.
I understand that, but that wasn't my question.  My question was, "Why
doesn't the resolver tag on the next domain name in the search directive
and search again until found or no more domains are left to search?"
Isn't that what the "search" directive is for?

Sorry if my original post wasn't clear.

-norm



On Thu, 2006-05-25 at 16:29 -0400, Kevin Darcy wrote:
> Right, the purpose of having multiple resolvers in the resolver list is 
> to enhance availability, not to accommodate disparate namespaces or get 
> a "second opinion" on lookups. All resolvers in the resolver list are 
> assumed to have the same data, temporary replication delays 
> notwithstanding. So, as soon as an answer is received from one resolver, 
> even if it's a SERVFAIL, NXDOMAIN, NODATA (a pseudo-RCODE meaning 
> NOERROR and an empty Answer Section, as you'd be getting here for 
> aj-mail1.ctc.com), it's treated as definitive and the other resolvers 
> are not consulted.
> 
>                                                                          
>                                        - Kevin
> 
> Norman P. B. Joseph wrote:
> 
> >Is this expected resolver behavior?  It doesn't fit my understanding,
> >but maybe my understanding is at fault.  The clients and servers in this
> >scenario are all BIND 9.2.4 under RHEL.
> >
> >I have the following search order in a client's resolver configuration:
> >
> >        search ctc.com ctcgsc.org ad.ctcgsc.org
> >
> >and I have the following two RRs in our DNS space:
> >
> >        aj-mail1.ctc.com.	MX	0 aj-mail1.ad.ctcgsc.org.
> >        aj-mail1.ad.ctcgsc.org.	A	10.x.x.x
> >
> >If I look for an A record for an unqualified "aj-mail1" the query fails,
> >but if I fully qualify the name in the query it succeeds.  I would have
> >expected the resolver to append the domains in the "search" directive in
> >order to the query name until it found "aj-mail1.ad.ctcgsc.org".
> >
> >I'm guessing that the resolver discovers the label "aj-mail1.ctc.com"
> >first, because of the order of domains in the "search" directive, but
> >since it is an MX record and not an A record the search fails, but the
> >resolver doesn't continue with the other search domains because of the
> >existence of the label.  Or something like that.
> >
> >What's the correct behavior?
> >
> >-norm
> >
> >
> >
> >
> >  
> >
> 
> 
> 
-- 
 Norman Joseph, System Engineer             joseph at ctc.com        IC|XC
 Concurrent Technologies Corporation         814/269.2633         --+--
 Information Systems Management Office (ISMO)                     NI|KA
  --=: It's not the voting that's democracy, it's the counting. :=--