[Dnsmasq-discuss] problem with wrong server being returned sometimes

[Simon Kelley]

Brad Langhorst wrote:
> I'm switching from tinydns + dnscache + dhcp server to dnsmasq.
> 
> Sometimes lookups seem to return the local server's ip address for
> external name lookups.
> 
> eg:
> amazon-images.blahblah.com  resolves to 192.168.10.2 (huh?)
> 
> maybe i've misconfigured something?
> 
> the problem seems to be much worse on my wife's os X 10.5 computer than
> on my linux machines.
> 
> If I configure dnsmasq to feed the existing dnscache server as a dhcp
> option 6, this problem does not manifest. That dnsmasq server the
> upstream server that dnsmasq uses when it's cache is empty.
> 
> 
> 
> here's my config:
> 
> domain-needed
> bogus-priv
> server=192.168.10.1
> 
> local=/home.langhorst.com/
> 
> address=/langhorst.com/192.168.10.2
> address=/langhorst.dyndns.org/192.168.10.2
> address=/bottle.home.langhorst.com/192.168.10.1
> 
> expand-hosts
> 
> domain=home.langhorst.com
> 
> dhcp-range=192.168.10.50,192.168.10.150,12h
> 
> dhcp-host=00:0d:93:4e:64:f8,charm,192.168.10.16
> dhcp-host=00:16:41:57:F7:C5,up,192.168.10.13
> 
> # default router - 3
> # DNS server - 6
> dhcp-option=3,192.168.10.1
> dhcp-option=6,192.168.10.1
> 
> dhcp-authoritative
> 
> 
> 
> 
How is the resolver set up on your clients? For Linux the config is in 
/etc/resolv.conf, Macs have something different, I guess.

I suspect you have something like

search langhorst.com

in /etc/resolv.conf.

Now, if for some reason, resolving www.google.com fails (like, a flaky, 
overloaded DNS server at your ISP) then the resolver code will try 
again, with the name

www.google.com.longhorst.com

That's caught be the line in /etc/dnsmasq.conf

address=/langhorst.com/192.168.10.2

and you get the answer 192.168.0.2

Setting the --log-queries option in dnsmasq should allow you to see 
exactly what's happening.

Cheers,

Simon.