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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