[dns-operations] Increasing the number of search path entries in a stub resolver

Nico CARTRON nicolas at ncartron.org
Wed May 4 07:39:55 UTC 2016

Hi Florian,

> On 04 May 2016, at 09:05, Florian Weimer <fweimer at redhat.com> wrote:
> Our stub resolver currently has a hard limit for 6 search domains that can be specified in /etc/resolv.conf.  We are considering lifting that limit.  Apparently, this is desirable for deployments which migrate from NIS host name lookups to DNS because NIS supports a larger number of default domain names (or something equivalent to that).
> From a larger ecosystem perspective, do you think that longer search paths would increase resolver load in an unacceptable way?  For example, host name lookups with a 10-element search path could easily require 20 queries.

How many search domains are you thinking of?
20? 50? No limit?

I've seen Windows clients with long lists (15+); while this didn't really affect resolution times seriously, there was a collateral effect: the cache was much bigger with of course a lot of NXDOMAIN for all the tested search domains. 


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