[Pdns-users] recursor fail to resolve

Aki Tuomi cmouse at cmouse.fi
Fri May 1 16:37:30 UTC 2020

> On 05/01/2020 6:31 PM Sergio P Cesar via Pdns-users <pdns-users at mailman.powerdns.com> wrote:
> I am new with pdns, just installed a resolver 4.3.0-rc2 to learn and all 
> seems to work but stumbled into an issue I cant resolve.
> My mailserver failed to deliver email to a few domains, in tracking it I 
> found that their DNS will drop the first packet on every new query  but 
> will respond on a second query ok and every one after that. (5 minutes 
> timeout) it will drop the 1st packet again.
> I was expecting the recursor to query the 2nd and 3rd server in their 
> list but it does not look like it is doing that.
> It seems like it is caching the failure and does not query again at all 
> for a while.
> I changed packetcache-servfail-ttl=0 and now it looks like after the 3rd 
> query attempt it will work as the far end server now respond.
> Not sure this is correct setting  or I will have adverse effect setting 
> this to 0.
> Perhaps I have not set something else that will tell the recursor to try 
> the next server if the first one fail to respond or send a second packet 
> or a retry.
> I used bind to test and it gets a response on the first try. I did not 
> try to trace the packets from a bind query.
> Thanks

Try `rec_control trace-regex domain.com` and post that. Without censoring the results.


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