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 From:  "Bryan K. Brayton" <bryan at sonicburst dot net>
 To:  <m0n0wall at lists dot m0n0 dot ch>
 Subject:  RE: [m0n0wall] DNS problem
 Date:  Mon, 21 Nov 2005 18:19:38 -0500
Well, I'm assuming that your laptop is configured to use the m0n0wall
lan IP as the first dns server, since you're getting the right IP
address initially, and I'm guessing you have a secondary dns server
configured on the laptop somehow too (either statically or by dhcp).

I don't think that nslookup will use the cached information from the
windows dns resolver, so it does happen sometimes that nslookup will use
your primary dns server, while your machine is actually using the
secondary dns server.  This can lead to different results.

For reasons I'm not quite sure about yet, I've seen Windows machines
switch to using the secondary dns server address.  I've usually been
able to trace this to a temporary unavailability of the primary dns
server.  If the scenario above is true, I'm not sure why your laptop
would be able to access a wan dns server, but not the resolver on m0n0,
except maybe if that process died or was unavailable/overloaded for some
reason.  I'd sniff the machine's traffic to find out just what dns
server it is using for normal dns lookups.

-Bryan

  
> -----Original Message-----
> From: Norman H. Azadian [mailto:norman at azadian dot ch]
> Sent: Monday, November 21, 2005 4:55 PM
> To: m0n0wall at lists dot m0n0 dot ch
> Subject: [m0n0wall] DNS problem
> 
> Someone want to tell me how this can happen?
> 
> > C:\>nslookup mail.azadian.ch
> > Server:  fw.azadian.ch
> > Address:  192.168.3.3
> >
> > Name:    mail.azadian.ch
> > Address:  192.168.3.10
> >
> >
> > C:\>ping mail.azadian.ch
> >
> > Pinging mail.azadian.ch [80.238.205.32] with 32 bytes of data:
> >
> > Reply from 80.238.205.32: bytes=32 time<10ms TTL=63
> 
> This is on my W2K laptop, which is connected to the mail server via
WLAN.
> mail.azadian.ch is DNS forwarded to mail server's internal address of
> 192.168.3.10 by m0n0wall-1.2.  When the laptop comes up, it runs
correctly
> for a while, meaning that both nslookup and ping use the internal
address.
>   Then it can't find the mail server, and I have the state shown
above.
> It
> is perhaps important to note that my ADSL is going up and down like a
yo-
> yo
> these days, due to either a bad modem or a bad line; I don't know
which
> yet.
> 
> NHA
> ---
> Norman H. Azadian    Taegerishalde 13    CH-3110 Muensingen
Switzerland
> norman at azadian dot ch      tel: +41 31 721 7855      fax: +41 31 55 898 55
>