[asterisk-users] Interoffice phone setup

[Col Ferguson]

----- Original Message -----
From: "Joseph L. Casale" <JCasale at activenetwerx.com>
To: "'Asterisk Users Mailing List - Non-Commercial Discussion'"
<asterisk-users at lists.digium.com>
Sent: Tuesday, June 10, 2008 10:47 AM
Subject: Re: [asterisk-users] Interoffice phone setup


> >I've seen this behaviour from Asterisk as well... while I can't say I
have
> >tracked it down and verified this... I've seen other talks about how
Asterisk
> >gets rather unhappy when it can't preform DNS queries.  I suspect that
may be
> >your problem.   Might want to check the archives for other issues that
people
> >have talked about DNS as a possible cause and see if there are any
> >similarities.
> >
> >--
> >Matt Watson
> >http://www.mattgwatson.ca
>
>
> Good info! I am on this now. I hope I find why so I can prevent this...
> Thanks!
> jlc


I had a recent experience the same.
The internet connection went down, and not even ZAP channels would work
anymore.
It seems that the guts of the problem (I think) is that Asterisk has a real
problem when it can't get DNS responses.

I found one forum post (a trixbox forum) that someone had worked out that
even if there was no SIP channels involved in a call, Asterisk still would
timeout on DNS before bridging ZAP channels. The post suggested creating a
dummy SIP trunk that registers to 127.0.0.1 and name it _something. This
apparently makes Asterisk check it first, Asterisk is then happy and can
bridge ZAP channels.

I have it fixed now by;
1. Running a DNS server with caching on the asterisk box, forwarding
requests to the ADSL router.
2. set srvlookup=no in sip_general_custom.conf (using freePBX, probably
really in sip.conf under [general])
3. created the _Dummy SIP trunk
4. put qualify=yes into any real SIP trunks.

1. Was what I thought might help. 2,3,4 were all google results.

As this was a production system, I didn't have time to try each of these to
see which would actually fix it, so implemented them all at once and then
tested.
They can now turn off their internet connection and everything works fine.
We left the internet down for 30mins.
I am worried that if the cache time on the DNS server runs out the problem
may come back, but this is set to 6 hours.

Hope this helps, and if anyone can shed some more light on this I'd
appreciate it. I'm still very much a novice.

Cheers,
Col