[PLUG] A DNS Question

Daniel Logghe dzl at frenetic.com
Tue Sep 28 02:15:03 PDT 2004


On Mon, 2004-09-27 at 15:52 -0700, Rich Shepard wrote:
>    In /etc/resolv.conf I have nameservers with my local server listed first.
> Now that I think I have re-installed dnscache I want to test that it is
> using the local box. However, if only 'nameserver 127.0.0.1' or 'nameserver
> 192.168.55.1' is uncommented I don't seem to get any response from outside
> the firewall.

What I suspect is happening is dnscache uses resolv.conf (probably
through the standard resolver library) to figure out which dns servers
to query when it doesn't know an answer. So when you list only localhost
it can only respond with stuff it already knows about. 

>    Is there a way to test what might be broken?

Use dig, or another dns query tool to directly query dnscache and makes
sure it is giving the result as opposed to your system trying the next
server listed in resolv.conf. Optionally you can use a packet sniffing
tool to watch for when dnscache sends a query to an external server. 

I'd give you hints on how to go about doing that, but it's been quite a
while since I've had to mess with all that and I've forgotten the
syntax. 





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