resolver options ..

Kevin Darcy kcd at daimlerchrysler.com
Wed Dec 7 22:54:04 UTC 2005


Claus van de Vlierd wrote:

>  Hallo ,
>
>  a) are these possible options available
>     in the "/etc/resolv"  - file (at least under
>      "RedHat AS 3")  like
>
>     "options timeout:3 attempts:1 rotate"
>
>
>     (which means , in my humble opinion :
>       "ask for a DNS-resolution  the first IP-address
>        in /etc/resolv.conf  only ONE time -- wait 3 seconds
>        for an answer -- and having received none  ask the next IP given
>        in "/etc/resolv !"  -- is this interpreatation correct ?!)
>
>
>      really being used by ordinary applications ?!
>
>   b) we still have the problem that our "sendmail" - daemon
>      (RedHat AS 3) doesn't seem to care about these options :
>       if the FIRST IP-address in "/etc/resolv.conf" does NOT answer to
>        a DNS (port 53) query it (the sendmail - daemon) doesn't process
>        any more -- instead of switching to the second IP address in
>        "/etc/resolv.conf" and repeating the query with that address .. !
>
>  c) do I MISUNDERSTAND something concerning this "resolv" - file   ----
>      OR is it the fault of the "sendmail"-daemon ?!
>       (applications like "ftp" , "scp" , Browsers etc. have NO problem
>        to use the second entry in case the first does NOT answer ..  !)
>
>   d) HOW con one FORCE to behave properly even when "the first entry" in
>      "/etc/resolv.conf" does NOT answer to DNS-queries ?!
>
>      perhaps  installing a caching DNS-Server on our Mail-System
>      ist the BEST (ONLY ?!?) solution ?!
>
>   e) thanx for a short hint -- and kind regards :
>
Not all resolver-library implementations support all resolv.conf 
options. sendmail implements DNS resolver code at a fairly low level, 
have you looked at the various Timeout.resolver.* options/suboptions 
within sendmail? Maybe you can tune them to your liking.

- Kevin




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