[Dnsmasq-discuss] Why dnsmasq got external DNS requests on one system and not another

[Simon Kelley]

On 27/05/14 11:14, Chris Green wrote:
> I think I have finally fathomed out why my new dnsmasq installation on
> my desktop machine didn't work whereas an apparently idetical setup on
> a small server did work.
>
> I *think* it's because Network Manager puts a file in /etc/dnsmasq.d
> that just has one directive in it:-
>      bind-interfaces
> I believe this is left there from the 'dnsmasq run by Network Manager'
> mode which is the default on [x]ubuntu systems.
>
> On the small server (where everything did work OK) the bind-interfaces
> directive didn't really do much as eth0 was already up and running
> when dnsmasq started so dnsmasq would listen on eth0.  However on my
> desktop machine, for whatever reason, eth0 takes a long time to start
> working (there are loads of messages about it in syslog at start-up
> time) and thus bind-interfaces stops dnsmasq from listening on eth0
> because it's not there when dnsmasq starts.
>
> I've fixed it on my desktop machine simply by removing the
> bind-interfaces directive.  Now there are no 'listen-address' or
> 'interface' directives (as per the original setup) and without the
> bind-interfaces directive dnsmasq listens on everything, which is
> OK on my small home LAN.
>
> Does this make sense?  I.e.  is my understanding correct?  ...  and
> again is it worth adding to the FAQ if my diagnosis is correct, I
> guess an interface being late to start up isn't *that* rare an
> occurrence.  Maybe just a note to say that one should remove the
> 'bind-interface' directive left there by Network Manager if installing
> a 'proper' dnsmasq.
>


One effect of "bind-interfaces" is exactly that dnsmasq only listens on 
interfaces hat exist when it starts up, so that's enough to explain what 
you saw. Well done for finding the problem.


Cheers,

Simon.