asterisk users - Jul 2006 - Using dproxy to solve "no DNS hangs everything" problem?

The subject pretty much says it.

Wondering if there's anyone out there who, as an alternative to 
hard-coding IP addresses in /etc/hosts, has implemented dproxy or 
somesuch to enable Asterisk to survive DNS outages.

I had a royal mess on my hands this morning after my Internet connection 
went down for a while.  No DNS = No Anything if there are FQDNs in the 
conf files.  The server hangs, affecting the Zap stuff too, which is WAY 
bad for me.

I need to bite this particular bullet.  My POTS line was offhook all 
morning because my Internet was out, and the first call that came in 
caused everything to freeze up and the channels were all hung.

Thanks.

B.

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> 
> The subject pretty much says it.
> 
> Wondering if there's anyone out there who, as an alternative to
> hard-coding IP addresses in /etc/hosts, has implemented dproxy or
> somesuch to enable Asterisk to survive DNS outages.
> 
> I had a royal mess on my hands this morning after my Internet
connection
> went down for a while.  No DNS = No Anything if there are FQDNs in the
> conf files.  The server hangs, affecting the Zap stuff too, which is
WAY
> bad for me.
> 
> I need to bite this particular bullet.  My POTS line was offhook all
> morning because my Internet was out, and the first call that came in
> caused everything to freeze up and the channels were all hung.
> 
This is a problem that affects more than just asterisk, so I'm sure
there are solutions out there!

One thing you might do is to put a trailing '.' on all fully qualified
DNS names. Without the '.', the system will first try appending the
default domain(s), which will cause extra lookups and delays. If all the
names that you care about can be resolved locally without needing the
internet then the trailing '.' should make it work much faster.

Of course, I'm assuming that you do have a local DNS of some sort, and
the delays you are seeing are caused by your systems thinking they want
to look up external names.

James

Yeah, I thought dnsmasq was the cure, too. We had an internet outage last
week. It was odd, our ISP (AT&T) changed out static IP's (don't
ask... No
one knows why... At least I figured out what was going on...). Thus, our
modem/router was whacked, as well as our firewall. So, I think every piece
of hardware saw the link as being up, but of course routing was not
operating. For clarity, dnsmasq is installed on our firewall, a PC that
routes traffic to our modem/router.

As far as I understand, the way dnsmasq works is that it proxys DNS requests
to your ISP's DNS servers (or wherever). At some point, if dnsmasq
determines that the upstream DNS servers are down/unreachable, then it will
respond to DNS requests with a failure/immediately timeout, thus precluding
Asterisk from hanging while it waits for a DNS query. Sounds like a good fix
for our problem, right?

Well, last week it did not behave well. Calls on Zap channels came in, they
would sit for several seconds (maybe 20-30, oddly some callers sat through
that silence just waiting!), then when no SIP phones could be found it would
go to the IVR (all attendants are busy, leave a message, etc...). All
connectivity with the SIP phones was gone, even trying to initiate a call
from the phones (Cisco _79[46]0's) to the Asterisk server was out. All
connectivity on the local LAN was good, even dnsmasq serving the local DNS
names.

Can anyone explain why Asterisk would not ring the SIP phones on our LAN?
The phones all register with the Asterisk server, the Asterisk server does
not need to look anything up to contact the IP's of the SIP phones on the
local LAN. I just don't know which direction to turn here.

>Thanks Brian for your work, I have had the same problem I installed
>dnsmasq and I *think* the problem is gone now, I'm repeating I think,
>I'll only know when the internet goes down again.

Sincerely,

Brent A. Torrenga

Torrenga Engineering, Inc.
907 Ridge Road
Munster, Indiana 46321-1771

tel:+1 219 836 8918 x325
fax:+1 219 836 1138
email:brent.torrenga@torrenga.com
web:www.torrenga.com