nslookup, dig, and host when name server is down

Gilles Espinasse g.esp at free.fr
Sun Apr 12 22:34:55 UTC 2009


----- Original Message ----- 
From: "Ming-Ching Tiew" <mctiew at yahoo.com>
To: <busybox at busybox.net>
Sent: Monday, April 13, 2009 12:12 AM
Subject: Re: nslookup, dig, and host when name server is down


>
>
>
> --- On Sun, 4/12/09, Gilles Espinasse <g.esp at free.fr> wrote:
>
> >
> > I suppose you did not define a local domain.
> > dnsmasq did not know it is not needed to forward
> > those related address
> > queries to the upstream servers. So everything is
> > forwarded
> > Apply the advice on this message
> >
http://lists.thekelleys.org.uk/pipermail/dnsmasq-discuss/2009q1/002807.html
> >
>
> OK then.
>
> Sound like the behaviour I need is not achievable with dnsmasq too.
>
> My desired behaviour is this: Cache whatever successful queries.
> When clients make queries, reply with cache entry if there is one,
> but asynchronously make an attempt to query upstream.  If successful,
> update cache. If fail, do nothing.
>
dont try to re-invent what exist
dnsmasq should work for your need

> This gives an absolutely responsive dns cache behaviour which
> does not slow down or block the clients.
>
When name server is down, don't try to use dig, nslookup or whatever
program.
Fix the reason why the name server is down.
This is not for nothing that you usually have 2 name server adresses.
The switch is made by dnsmasq (tranparently except the little delay related
to the first server timeout and the new election)

    Gilles



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