bind 9.11.3 - resolving troubles running as a caching server

[Ondřej Surý]

Hi,

you mentioned “forwarders” - what are these and how does AAAA answer look like on the upstream forwarders?

I would recommend enabling higher debug level (start with -d 1) and look into logs what was the answer from the forwarders preceding the failure.

Ondrej
--
Ondřej Surý — ISC

> On 20 Nov 2019, at 18:44, Bind Mailinglist <bindbandbund at ggaweb.ch> wrote:
> 
> Hello list
> I'm glad there is such an active list. Hope there is anybody out there
> who can help me with my little problem. :-)
> We are running six bind server ( all Ubuntu LTS 18.04 with bind 9.11.3
> ), so they are pretty up to date.
> Three of them have authoritative zones, one is for testing and two are
> just caching servers. And there starts my problem.
> 1. It only appears on my caching servers and only if I use my other
> servers as forwarders.
> 2. At the moment the problem appears on my chaching servers I'm still
> able to let it resolve through my forwarders.
> 3. Only one organisation with several newspapers are affected. There may
> be others but I don't know at the moment.
> 
> Ok, all these newspapers are hosted on oraclecloud with short timers
> around 30s.
> 
> # dig www.20min.ch
> ;; ANSWER SECTION:
> www.20min.ch.           39      IN      CNAME  
> tamedia.a.inregion.waas.oci.oraclecloud.net.
> tamedia.a.inregion.waas.oci.oraclecloud.net. 16 IN CNAME
> tm.inregion.waas.oci.oraclecloud.net.
> tm.inregion.waas.oci.oraclecloud.net. 16 IN CNAME
> eu-london.inregion.waas.oci.oraclecloud.net.
> eu-london.inregion.waas.oci.oraclecloud.net. 28 IN A 138.1.82.213
> eu-london.inregion.waas.oci.oraclecloud.net. 28 IN A 147.154.234.67
> eu-london.inregion.waas.oci.oraclecloud.net. 28 IN A 147.154.228.138
> 
> # dig www.tagesanzeiger.ch
> ;; ANSWER SECTION:
> www.tagesanzeiger.ch.   113     IN      CNAME   cnp-a-cre-p.newsnetz.ch.
> cnp-a-cre-p.newsnetz.ch. 113    IN      CNAME  
> tamedia.a.inregion.waas.oci.oraclecloud.net.
> tamedia.a.inregion.waas.oci.oraclecloud.net. 11 IN CNAME
> tm.inregion.waas.oci.oraclecloud.net.
> tm.inregion.waas.oci.oraclecloud.net. 12 IN CNAME
> eu-switzerland.inregion.waas.oci.oraclecloud.net.
> eu-switzerland.inregion.waas.oci.oraclecloud.net. 12 IN A 192.29.59.121
> eu-switzerland.inregion.waas.oci.oraclecloud.net. 12 IN A 192.29.58.46
> eu-switzerland.inregion.waas.oci.oraclecloud.net. 12 IN A 192.29.58.42
> 
> 
> Now if I use my caching servers with forwarders enabled I run quite
> often into cases where resolving stops working for theses two domains at
> the same time.
> When I take a dump I see the following line:
> ; answer
> tm.inregion.waas.oci.oraclecloud.net. 893 \-AAAA ;-$NXRRSET
> 
> I have to clear this host from cache to make it working again, for a few
> minutes.
> The stupid thing, this NXRRSET cache entry has a much higher lifetime.
> And so resolving stops working on my caching servers for more then 15min.
> 
> Any idea how I could find out why this happens?
> There must be something between my DNS servers. They are in the same
> network, so there is no firewall between.
> 
> Many thanks and regards
> Florian
> 
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