[Pdns-users] how do query the recursor cache to see what's in it?

Alfred B. M. Cordero otto-pilot at hushmail.com
Thu Mar 10 16:49:02 UTC 2011

On Thu, 10 Mar 2011 06:00:11 -0800 Kenneth Marshall <ktm at rice.edu> 
>On Wed, Mar 09, 2011 at 03:13:03PM -0800, Alfred B. M. Cordero 
>> On Wed, 09 Mar 2011 14:30:23 -0800 Kenneth Marshall 
><ktm at rice.edu> 
>> wrote:
>> >You can use "rec_control dump-cache filename" but the
>> >recursor will not answer queries while that cache is being
>> >dumped.
>> >
>> >Have you checked your network gear to see if you are
>> >discarding network packets. UDP is prone to that and
>> >it could cause service problems. But I would not
>> >attribute them to the recursor...
>> Thank you Ken. rec_control worked great and I read about the 
>> negative
>> values.
>> We have not seen this problem with other dns.
>Another source of network problems could be caused by a
>firewall device that tries to be too smart and either
>delays the traffic or outright mutilates it. I do not
>know your setup, but we dealt with an issue caused by
>the security features of pdns-recursor, the randomized
>source port.

djbdns also uses randomized source ports (don't all dns now?) but 
shown no
similar patterns.  Our env. is a simple LAN running pdns recursor. 
No other dns
on the LAN.

We are looking at bandwidth-limiting by the isp. If we have 256Kb 
link we don't
know how that is capped. But as you say,  they are maybe mutilated.
Once at 256Kb any other traffic is dropped. There are probably many 
different ways
to do bandwidth-limiting.

If there is anything we can do we will try it. Maybe we can do 
something with QoS.
But it is a new area so if you have any hints to share it may help.

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