[Blink] DNS lookup failure

Dan Pascu dan at ag-projects.com
Wed Jan 5 11:32:37 CET 2011

On 21 Dec 2010, at 11:06, Conrad Heiney wrote:

> The notification and sip logs are attached.
> The DNS servers do in fact return NX on the command line. However, blink reports a timeout.

I cannot reproduce this. I tried the DNS lookups that blink does, using blink's own lookup function on your domain and it immediately returned the correct answer with no timeout whatsoever. The only difference is that it was using my resolver.

I don't know if it works because you have fixed something since, but if not and you still see the problem in your environment, the issue must to be somewhere in your resolver. Unfortunately I cannot trace that since I have no access to your private resolver.

What you can do however to avoid the problem is to add a NAPTR record that indicates that you only support UDP, so it won't even try to lookup the TCP and TLS SRV records that give the timeout.

Another thing you can try in order to identify the source of your problem is to use the Google nameservers in your /etc/resolv.conf ( and instead of your local resolver ( If they work, but your local resolver gives a timeout, then the issue needs to be investigated further in your local resolver.

Attached is a script that uses the same code as blink to do the DNS lookup. Run it with "python lookup.py"
It does the whole DNS lookup for voip.tierzero.net. In my case it returns immediately with the correct answer (but again it uses my own resolver not your private one):

$ time python lookup.py
[Route('', 5060, 'udp')]

real    0m0.288s
user    0m0.247s
sys     0m0.040s

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