does bind depends on system DNS settings for lookup?

[Stuart Browne]

-----Original Message-----
> From: bind-users-bounces at lists.isc.org [mailto:bind-users-bounces at lists.isc.org] On Behalf Of Dil Lee
> Sent: Wednesday, 18 November 2015 3:42 PM
> To: bind-users at lists.isc.org
> Subject: does bind depends on system DNS settings for lookup?

> Hi,
> This is probably a dummy question.
> My understand of bind in handling non-authoritative queries is:
> 1) forward mode. It just forward the client queries to an upstream DNS
> server, which is defined in "forwarders" directive.

I don't think BIND forwards the request on at the packet level but proxies (creates a new request stuffing the question et al into the packet), but basically, yes.

> 2) recursive mode. It actually start asking from root DNS server, then
> 2nd level DNS server etc till it finally get an authoritative answer
> for the host in question.

This is correct.

> Non of these modes seems to depends/relates to the system DNS settings
> on the host which bind is running on, e.g. /etc/resolv.conf . AMIRITE?

What you are talking about here is a "Stub Resolver"; the OS has sufficient libraries to ask a name server for a result. It has no concept of forwarding or recursing, just "Give me an answer please!".

I believe any system that has an IP layer (and most likely others) has a stub resolver built into the core libraries. The stub resolver doesn't use BIND's libraries directly (thus no BIND needs to be installed to do DNS lookups as a client).

> Regards,
> Dil

Stuart