Gauvin Repuspolo glr0221 at
Wed Oct 24 05:30:55 UTC 2007

Hello danny and mark,
Thanks for all your answers.

As of this moment, I cant really confirm whether RES_BLAST is really
implemented in the bind9 library. My limited skills, as far as I can
muster,  produced a "grep" result that RES_BLAST is only referenced to, when
the bind library makes the decision to execute the RES_ROTATE action.

It seems that, RES_BLAST is not configurable also from "resolv.conf" file's
"options" settings. Being a newbie and all, I don't know if implementing a
simulaneous DNS lookup/query to multiple nameservers would prove to be
disastrous to a network, that is why bind9 seems to have no interface to set
the RES_BLAST option. (Again I may be wrong here.)

I agree with you totally on the behaviour of some unix resolvers when the
first name-server listed becomes unreachable. Aside from this, I intend to
take a look at how RES_BLAST will handle situations where nameserver 1
returns an NXDOMAIN and nameserver 2 responds with an authoritative result.

As for creating my own name server, is there a way for me to mimic the
effect of RES_BLAST using an IP forwarder. What I mean is, I setup an ip
forwarder, delcare two root zones (if this is even possible), within my
named.conf file so that the daemon is forced to lookup the forward list of
both root zones? Is it even possible to have two root zones? As for lwresd,
I am not yet familiar with it and will look into it also.

I hope I make sense.

Thank you all so much for the assistance,

On 10/24/07, Danny Thomas <d.thomas at> wrote:
> >       RES_BLAST is available in lib/bind
> It would be great if you could make RES_BLAST the default in resolv.conf,
> as it would overcome the bad behaviour of the (unix) resolver when the
> first name-server listed becomes unreachable. Mind you, I don't know
> whether resolv.conf directives would come from bind, or whether it
> is code managed by the OS people importing bind code in the library.
> I know there are other approaches which do keep track of how quickly
> name-servers respond, and which soon learn when a name-server is unreach-
> able, but these involve daemons like a caching name-server or lwresd.
> So resolving is affected if the daemon dies.
> Danny
> --
>   d.thomas at    Danny Thomas,
>          +61-7-3365-8221    Software Infrastructure,
>    ITS, The University of Queensland

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