[asterisk-users] Losing local SIP phones when internet goes down?

[Randy R]

On Fri, Feb 5, 2010 at 8:41 AM, Olle E. Johansson <oej at edvina.net> wrote:
>>> What I have seen on my asterisk box when I had a up/down adsl line was
>>> that the asterisk box couldn't do dns resolution and would hang( well no
>>> other internal calls could be made, seemed like some sort of semaphore
>>> was stuck) when the adsl came up and dns could be done, everything
>>> worked fine again

Confirmed and experienced years ago in a release far, far away.

> Yes, that is the case. Asterisk doesn't have asynchronus DNS support, so in order to work when the link is down, you need a local resolver, like a caching BIND server, on the same host. The calls to DNS resolvers in Asterisk is synchronus, so Asterisk will wait for the response to arrive.

IIRC, at the time I had this problem, asterisk did not answer analog
phone lines either so as a company we had no phones and had to revert
to regular telephones plugged into the wall. Even if Internet is
working, if the configured DNS is down, you're still sunk. This sorely
needs to be fixed IMO.

/r