forwarder selection logic by bind9

[Barry Margolin]

In article <mailman.0.1542618692.716.bind-users at lists.isc.org>,
 József Lázár <jozsef.gabor.lazar at gmail.com> wrote:

> Did you have a chance to look at my email below? Thanks again, Joe

Have you tried googling "bind smoothed round trip time"?

> 
> On Tue, 13 Nov 2018 at 10:42, József Lázár <jozsef.gabor.lazar at gmail.com>
> wrote:
> 
> > Ok, I see. However, could you please specify this "time to time" period?
> > Does it depends of the dns traffic which the bind receives?
> > I've tried the following scenario:
> > Configured two dns forwarders, both of them worked at the beginning. After
> > one minute I turned off the first dns forwarder and after an another minute
> > I restarted it.
> > Then I sent one dns request to bind in every 1,5 second for over one hour,
> > but the first dns server didn't receive any request after the restart.
> >
> > Thanks, Joe
> >
> > On Sun, 11 Nov 2018 at 15:06, Matus UHLAR - fantomas <uhlar at fantomas.sk>
> > wrote:
> >
> >> On 10.11.18 15:59, József Lázár wrote:
> >> >I'm wondering what the selection logic in bind for forwarders. I tried to
> >> >look for this information in the official documentation but couldn't find
> >> >it. Could you please describe it for me briefly?
> >> >
> >> >Actually, the scenario is that I have two DNS servers and I'm using bind
> >> to
> >> >forward only the incoming DNS requests and if the "primary" one is failed
> >> >for a short period of time then the bind will try to use the "secondary"
> >> >one, but when the "primary" comes back, then it doesn't try to connect to
> >> >it at all, only if the connection breaks for the "secondary" server.
> >> >
> >> >Is there any way to configure this logic somehow?
> >>
> >> No. BIND technically choses server that responds faster. If one of servers
> >> doesn't respond (it's down), BIND uses the another one. However, time to
> >> time, BIND rechecks the other server(s) to see if situation has changed.
> >>
> >> BIND does not differ between servers as primary and secondary.
> >>
> >> --
> >> Matus UHLAR - fantomas, uhlar at fantomas.sk ; http://www.fantomas.sk/
> >> Warning: I wish NOT to receive e-mail advertising to this address.
> >> Varovanie: na tuto adresu chcem NEDOSTAVAT akukolvek reklamnu postu.
> >> They that can give up essential liberty to obtain a little temporary
> >> safety deserve neither liberty nor safety. -- Benjamin Franklin, 1759
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> >

-- 
Barry Margolin
Arlington, MA