option forward question

[Kevin Darcy]

If your nameserver has the answer already (because it's in an authoritative
zone or because it's been cached from a previous query), then it will *not* use
the forwarders to resolve the name. "forward first" has nothing to do with
this. "forward first" only affects what your nameserver does if it tries to
forward a query and none of the forwarders are available. If "forward first" is
in effect, in that situation it will then try to resolve the name without using
forwarding. If "forward only" is in effect, in that situation it will just give
up. So you should only use "forward first" if your nameserver is capable of
resolving *any* name without using forwarding. What I usually say is that
"forward first" is only appropriate when you are using forwarding purely for
purposes of enhancing query performance.

As for stub resolvers using your nameserver, they don't know and don't care
whether your nameserver is using forwarding or not. They just use nameservers
in the order specified in /etc/resolv.conf or whatever.


- Kevin

Jean-Christian Imbeault wrote:

> A simple question on the forward option. I have read the both the DNS&BIND
> book and the BIND 9 ARM but still am confused as to what forward actually
> does.
>
> My question boils down to this: if I use a forwarders list does that mean
> that the DNS servers listed therein get queried *before* my local DNS
> server? I'm asking because it seems kind of silly to query other DNS servers
> for hosts that my local server can answer for ... Especially since my server
> is for a local LAN and the "upstream" DNS server can't answer for local
> names at all.
>
> I have the following:
>
> options {
>         directory "/var/named";
>          query-source address * port 53;
>          forward first;
>          forwarders {
>              165.76.16.2;
>              165.76.8.2;
>          };
> };
>
> Does my local DNS server answer first or second for hosts it knows about? If
> I remove the "forward first" option will that make my local DNS server
> answer first for hosts it knows about?
>
> Thanks,
>
> Jc
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