really weird(?) DNS setup on linksys router running DD-WRT

[Lennart Sorensen]

On Mon, Sep 21, 2009 at 10:23:52AM -0400, Robert P. J. Day wrote:
>   i figure i might as well bug the tlug list on this one, since the
> location is in TO.
> 
>   was helping someone install some linux software this weekend, and
> there seemed to be intermittent network problems (losing ssh login
> sessions), as well as DNS resolvability errors.
> 
>   took a look at a couple of the internal linux systems (call them
> 192.168.1.100 and 192.168.1.101), and their /etc/resolv.conf files
> read:
> 
>   nameserver 127.0.0.1
>   nameserver 192.168.1.1   (the router)
>   search domain1 domain2

resolv.conf controls what the router uses to resolve dns queries.
It has no effect on how clients behind the router get DNS at all.
Does the router have any need for external DNS at all really?

Clients that use the router for dns will get whatever the nameserver on
port 53 of the router is configured to do (and it never cares at all about
/etc/resolv.conf).  Any box that has a nameserver installed will usually
have resolv.conf point at itself to talk to its own nameserver on port 53.
Very sensible setup.

> ok, i thought, they'll try to access the router for DNS info.  but
> when i browsed over to the router, it was set up for DNS statically
> with the first two entries:
> 
>   192.168.1.100
>   192.168.1.101

So it can offer DNS service to the local network.  It is almost certainly
configured to offer forwarding to an outside DNS for anything it doesn't
know itself.  Perfectly normal setup.

> am i just confused?  that makes no sense to me.  the internal systems
> will consult the router for DNS, while the router turns around and
> consults the internal systems?  am i missing something here?
> shouldn't the router be set up to consult 3 *external* DNS servers, as
> supplied by whoever their network provider is?  or am i just being
> clueless?

I suspect it is completely normal, and you just need to learn how DNS
and name resolution works.

-- 
Len Sorensen
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