[Pdns-users] recursor fail to resolve

Otto Moerbeek otto at drijf.net
Mon May 4 08:22:47 UTC 2020


On Fri, May 01, 2020 at 11:31:21AM -0500, Sergio P Cesar via Pdns-users 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

Please share your full config and the names involved. It now is a
guessing game.  

The recursor tries other auth nameservers if one fails. But there are
also other factors that could play a role. Unless you share your
complete config and the actual names that cause trouble, it is
impossible to help you.

Also, the final 4.3.0 is out, so please upgrade the rc2 you are running.

        -Otto


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