Hi Ben, thanks for the answer.
Yeah, I think you are right. I see a lot of udpInOverflows on the system, which suggest that the receive buffer is too small indeed. Is there any kind of recommendation or best-practice advice what the buffers should ideally be set to on Solaris ? I did search the ISC Knowledge Base, but didn't find any useful advice. Regards arc On 06/28/17 14:37, Ben Croswell wrote: > Have you checked deeper at the OS level? I have seen on Linux DNS servers > silent drops of queries on very busy servers that were exhausting UDP > receive buffers. > > On Jun 28, 2017 10:26 AM, "Marc Richter" <marc.rich...@de.verizon.com > <mailto:marc.rich...@de.verizon.com>> wrote: > > Hi, > > we have a setup here consisting of a recursive DNS server and two > monitoring servers. The monitoring servers sent a test query to the DNS > server once every two minutes to check if it is answering properly. > > We now have the problems that these test queries are timing out from time > to time, (correctly) resulting in alarms in our monitoring system. > > I have checked this now and noticed that each time we see that alarm, the > query sent by the monitoring server is not being answered at all. > To debug that I ran tcpdump on both the monitoring server and the > recursive > DNS server. I see the query being sent out on the monitoring server and I > also see the query being received on the DNS server, however there is no > response sent to this query at all. > Looking at the query log, which I enabled temporarily, the query is also > not logged there so it looks like BIND is ignoring that query somewhere, > although it is properly received by the IP stack of the server. > > Do you have any suggestions how to debug this further, to hopefully find > out where these queries are stuck/dropped/ignored, as I have run out of > ideas ? > > The environment is: > BIND 9.9.9-P5 (Extended Support Version) <id:1ab232a> > running on SunOS sun4v 5.11 11.3 > > > Thanks ! > Marc > _______________________________________________ > Please visit https://lists.isc.org/mailman/listinfo/bind-users > > <https://urldefense.proofpoint.com/v2/url?u=https-3A__lists.isc.org_mailman_listinfo_bind-2Dusers&d=DwMFaQ&c=udBTRvFvXC5Dhqg7UHpJlPps3mZ3LRxpb6__0PomBTQ&r=wDgZv-d1RrBMzWr_7pSF_09ZAXIr59EgoXQU4ctOHMk&m=t6jk-SZ5v_kNlupaNbpfob7Dm6Iddy_gUndDBwWnkmc&s=Ko40xVILMIdx3tQ9ElkdPqboTH8RpH1ZKJ4ZXcGp9NM&e=> > to unsubscribe from this list > > bind-users mailing list > bind-users@lists.isc.org <mailto:bind-users@lists.isc.org> > https://lists.isc.org/mailman/listinfo/bind-users > > <https://urldefense.proofpoint.com/v2/url?u=https-3A__lists.isc.org_mailman_listinfo_bind-2Dusers&d=DwMFaQ&c=udBTRvFvXC5Dhqg7UHpJlPps3mZ3LRxpb6__0PomBTQ&r=wDgZv-d1RrBMzWr_7pSF_09ZAXIr59EgoXQU4ctOHMk&m=t6jk-SZ5v_kNlupaNbpfob7Dm6Iddy_gUndDBwWnkmc&s=Ko40xVILMIdx3tQ9ElkdPqboTH8RpH1ZKJ4ZXcGp9NM&e=> > > -- Marc Richter Engr III Cslt-Ntwk Eng&Ops Sebrathweg 20 44149 Dortmund Germany O +49 231 972 1293 F +49 231 972 2587 E marc.rich...@de.verizon.com _______________________________________________ Please visit https://lists.isc.org/mailman/listinfo/bind-users to unsubscribe from this list bind-users mailing list bind-users@lists.isc.org https://lists.isc.org/mailman/listinfo/bind-users
