[Pdns-users] CNAME to non locally hosted domain

bert hubert bert.hubert at netherlabs.nl
Thu May 4 16:19:41 UTC 2006

On Thu, May 04, 2006 at 05:35:18PM +0200, Richard Mayhew - Nashua Broadband wrote:
> Could someone explain to me how PowerDNS handles CNAME's that resolve to
> a entry that is not part of a locally hosted domain.

Ok, there are two cases. If no recursor is configured, or of the question
did not ask for recursion, PowerDNS responds with the CNAME and a ServFail,
as per the RFC. If so configured, PowerDNS will respond with a 'root
referral', but it is the same thing.

This works well in practice, recursors understand this.

If a recursor is configured AND the packet requests recursion (try this with
'dig +norecurs' or 'dig +recurs', the default) , it depends a bit. If
'lazy-recursion' is configured, only the target of the CNAME is sent to the
recursor. This is the default.

If lazy-recursion is off, the *entire* question would be handed off to the
recursor immediately, so the local database would not be queried.. but the
recursor might do that for us.

I realise this is complex, but by default we do the right thing for almost

Let me know if you need more explanation.

Kind regards,

bert hubert

http://www.PowerDNS.com      Open source, database driven DNS Software 
http://netherlabs.nl              Open and Closed source services

More information about the Pdns-users mailing list