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

[--[ UxBoD ]--]

----- "Olle E. Johansson" <oej at edvina.net> wrote:

> 5 feb 2010 kl. 09.28 skrev --[ UxBoD ]--:
> 
> > ----- "Randy R" <randulo2008 at gmail.com> wrote:
> > 
> >> 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
> > 
> > Why not run a internal DNS with forwarders to your ISP ? That way
> Asterisk can still resolve itself and hosts internally.
> > 
> See above:
> >> you need a local
> >> resolver, like a caching BIND server, on the same host. 
> 
> /O :-)

Doh! :) My philosophy has always been to install a local named server, whether it be for Asterisk or something else, as most of the time everything I do is behind NAT and I prefer to resolve internal addresses.  This also help if you run your own mailserver and make extensive queries to RBLs etc.
-- 
Thanks, Phil