[asterisk-users] sip trunk failing to register causes sip phones to become unreachable

[Warren Selby]

On Aug 23, 2012, at 10:30 AM, John Cahill <john at dmcip.com> wrote:
> I have only seen this problem when using sipgate SIP trunks which actually "register". If the ADSL connection goes down that the sip trunk uses, the sip phones registered locally become unreachable. This happens on any 1.6.x or 1.8 version of asterisk I've tried. Is there a work around that doesn't involve putting an opensips server between the asterisk server and the sip trunk?

This is a common issue that I've seen many times.  The problem has to do with DNS cache look-ups and timeouts.  What typically solves it for me is to install a local cacheing-only DNS server on the asterisk box and point the resolvers on the asterisk box to itself.  This will only solve the issue of an internet outage causing the sip phones to stop working, and only for as long as the local cache stays relevant.  If there is a power outage that takes out both the asterisk server and the internet, and your asterisk box comes up but your internet doesn't, this won't work.  


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Thanks,
Warren Selby, dCAP