asterisk users - Oct 2013 - Extensions fail to register themselves when all trunks are unreachable.

Hi,
my asterisk server has a strange behavior when all trunks are
unreachable (for example due to internet connection), it doesn't accept
registrations from any internal extension, and, obviously, I can't do
any internal call.

On the log I see only lines like:

[2013-09-30 01:35:04] NOTICE[1827] chan_sip.c: Peer 'xxx' is now
UNREACHABLE!  Last qualify: 36

and then

[2013-09-30 01:35:07] NOTICE[1827] chan_sip.c: Peer 'yyy' is now
Reachable. (36ms / 2000ms)

How can I troubleshot this issue?

Thank you very much in advance.

Francesco Namuri

On Tuesday 01 October 2013, Francesco Namuri wrote:
> Hi,
> my asterisk server has a strange behavior when all trunks are
> unreachable (for example due to internet connection), it doesn't accept
> registrations from any internal extension, and, obviously, I can't do
> any internal call.
Asterisk really, really does not like not being able to see a DNS server, even 
if you think you have configured everything using IP addresses and hostsfile 
entries.  It won't allow even internal calls if it cannot see any name 
servers.

One way to deal with this is to install bind9 *on the Asterisk server itself*, 
and put "nameserver 127.0.0.1" in /etc/resolv.conf.

-- 
AJS

Answers come *after* questions.