[Pdns-users] potential side effects of ALIAS records

Pieter Lexis pieter.lexis at powerdns.com
Wed Feb 8 17:53:39 UTC 2017

Hello Klaus,

On Wed, 8 Feb 2017 16:48:19 +0100
Klaus Darilion <klaus.mailinglists at pernau.at> wrote:

> - Will outstanding recursion somehow block or slow down the answering of
> normal ressource records?

Resolving the answer of an ALIAS record will block only the query that initiated it.

> - Will the expanded ALIAS result locally cached? (besides the packet
> cache, e.g. based on TTL or is it the job of the resolver to cache)

This is the job of the resolver. Apart from the packet cache, ALIAS is resolved each time when needed.

> - IS it correct that ALIAS is not activated unless I explicitly
> configure "recursor=..."?

If you have resolvers set in /etc/resolv.conf, these nameservers will be used as recursors.

> - If ALIAS is not enabled, will PDNS just ignore these records?

ALIAS is always "enabled". When we encounter an ALIAS record for the name queried, it is expanded.

> Any other things I need to know? I am a bit concerned doing potential
> time consuming activities on my name servers.

What do you mean by this?

Best regards,


Pieter Lexis
PowerDNS.COM BV -- https://www.powerdns.com

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