I have been running Asterisk 1.4 for a few years now.  I have three providers which I have never had any issues with and Asterisk has been running fine.

I changed to Snap's SIP service earlier this year and have managed to get it essentially working OK, but I am having one minor problem that (judging by the absence of other posts) no one else is having.

I have the server set up as connect1.plus.snap.net.nz.  This will map me to either wlgacme01.plus.snap.net.nz or chcacme01.plus.snap.net.nz.  The wlg server is 123.255.8.74 and the chc server is 123.255.8.82.

The problem I am having is that sometimes I get a 403 Forbidden error when trying to make an outgoing call and incoming calls result in number unobtainable tone (I don't have voicemail).

I think the problem may be related to the IP addresses.  If I do a sip show peer 07xxxxxxx command in Asterisk, I get a ToHost of connect1.plus.snap.nz (which is correct) and an IP address of one of the two Snap servers.

Asterisk tells me what it is trying to map to like this:
ast_get_srv: SRV lookup for '_sip._udp.connect1.plus.snap.net.nz' mapped to host chcacme01.plus.snap.net.nz, port 5060

What seems to be happening is that when calls are failing, I am being told that I am connecting to either chcacme01 or wlgacme01 but when I do a sip show peer command the IP address shown is for the other server, ie I get the above mapping line indicating the chc server but the IP address will be 123.255.8.74 (the wlg server).   If I wait long enough, the IP address updates and things start working again.

I have tried setting the DNS refresh to 60 seconds (the default was 3600) and it makes no difference.

The only thing that I have found that gets things working again is to do a reload (full, not just SIP).  To this end, I have stuck a crontab line in that reloads asterisk every two minutes.  While this seems to be working fine, it seems tacky so I thought I would see if any experts out there could offer me some advice.

Thanks.