[asterisk-users] DNS

[Rich Adamson]

Bill Gibbs wrote:
> Asterisk server is setup in /etc/resolv.conf to query my primary and 
> backup NS.  Had an issue with my primary NS and asterisk refused to 
> complete any calls or forward inbound calls to extensions.  I had to 
> manually switch it to look at the backup NS first then reboot for it to 
> start working while I fixed the primary.  Is this behavior normal or am 
> I missing a step?  All hosts, etc are identified by IP.
> 
>  
> 
> Ver 1.2.10

Most people don't think much about dns, but if your primary dns server 
responded with "anything" (including a simple I don't know response), 
the secondary dns server will not be attempted.  So, depending upon 
exactly what was wrong with your primary, your stated result can be very 
normal.

Regarding asterisk stop responding when no dns server is present, that's 
been discussed many many times on this list, the latest as of earlier 
this week. Asterisk code does have a problem, and I'd be reasonably 
certain part of the problem is the OS underlying dns resolver operates 
in a blocking mode.

In the past, one of the suggested workarounds was to implement a dns 
caching-only server on the asterisk box. I've not done that and I don't 
recall hearing anyone's actual experience after doing it.

Another suggested workaround is to use IP addresses only in your configs 
(which is what I've been doing for three years). But, you'll need to 
make sure nothing in the configs gets interpreted as a dns name.