[Pdns-users] pdns forward nested recurse possible?

[Brian Candler]

On 19/04/2019 09:48, abubin wrote:
> Is it possible to use recursor to forward all queries to pdns 
> authoritative server and if that query fails, it will forward all to 
> public DNS such as 8.8.8.8?

I don't think so.  (In any case, define what you mean by "failure" - 
REFUSED? SERVFAIL? NXDOMAIN? Something else?)

You might be able to do something funky like that with dnsdist, but I 
prefer DNS to work deterministically.


>
> For example, in my pdns, I have create a domain called mydomain.com 
> <http://mydomain.com> and yourdomain.moc.
>
> So instead of creating:
> forward-zones=mydomain=127.0.0.1:5300 <http://127.0.0.1:5300>
> forward-zones+=yourdomain.moc=127.0.0.1:5300 <http://127.0.0.1:5300>
> forward-zones-recurse=.=8.8.8.8
>
> I would like to create:
> forward-zones-recurse=.=127.0.0.1:5300 <http://127.0.0.1:5300>
> forward-zones-recurse+=.=8.8.8.8
>
> However, tried second method and it does not work. Please advise.

You could try using forward-zones-file to list all your domains which 
need to be forwarded:

mydomain.com=127.0.0.1:5300
yourdomain.moc=127.0.0.1:5300
+.=8.8.8.8

I am not sure about the last line, as I've never used pdns-recursor as a 
dumb forwarding cache.  I prefer to let it do its own recursion and not 
trust a third-party cache.

Also see the note about negative trust anchors at 
https://doc.powerdns.com/recursor/settings.html#forward-zones


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